diff --git a/packages/core/src/blocks/HeadingBlockContent/HeadingBlockContent.ts b/packages/core/src/blocks/HeadingBlockContent/HeadingBlockContent.ts
index 8299892a0..f008b53b1 100644
--- a/packages/core/src/blocks/HeadingBlockContent/HeadingBlockContent.ts
+++ b/packages/core/src/blocks/HeadingBlockContent/HeadingBlockContent.ts
@@ -10,9 +10,11 @@ import {
 import { createDefaultBlockDOMOutputSpec } from "../defaultBlockHelpers.js";
 import { defaultProps } from "../defaultProps.js";
 
+const HEADING_LEVELS = [1, 2, 3, 4, 5, 6] as const;
+
 export const headingPropSchema = {
   ...defaultProps,
-  level: { default: 1, values: [1, 2, 3] as const },
+  level: { default: 1, values: HEADING_LEVELS },
 } satisfies PropSchema;
 
 const HeadingBlockContent = createStronglyTypedTiptapNode({
@@ -26,7 +28,7 @@ const HeadingBlockContent = createStronglyTypedTiptapNode({
 
   addInputRules() {
     return [
-      ...[1, 2, 3].map((level) => {
+      ...HEADING_LEVELS.map((level) => {
         // Creates a heading of appropriate level when starting with "#", "##", or "###".
         return new InputRule({
           find: new RegExp(`^(#{${level}})\\s$`),
@@ -58,63 +60,29 @@ const HeadingBlockContent = createStronglyTypedTiptapNode({
   },
 
   addKeyboardShortcuts() {
-    return {
-      "Mod-Alt-1": () => {
-        const blockInfo = getBlockInfoFromSelection(this.editor.state);
-        if (
-          !blockInfo.isBlockContainer ||
-          blockInfo.blockContent.node.type.spec.content !== "inline*"
-        ) {
-          return true;
-        }
-
-        // call updateBlockCommand
-        return this.editor.commands.command(
-          updateBlockCommand(blockInfo.bnBlock.beforePos, {
-            type: "heading",
-            props: {
-              level: 1 as any,
-            },
-          }),
-        );
-      },
-      "Mod-Alt-2": () => {
-        const blockInfo = getBlockInfoFromSelection(this.editor.state);
-        if (
-          !blockInfo.isBlockContainer ||
-          blockInfo.blockContent.node.type.spec.content !== "inline*"
-        ) {
-          return true;
-        }
-
-        return this.editor.commands.command(
-          updateBlockCommand(blockInfo.bnBlock.beforePos, {
-            type: "heading",
-            props: {
-              level: 2 as any,
-            },
-          }),
-        );
-      },
-      "Mod-Alt-3": () => {
-        const blockInfo = getBlockInfoFromSelection(this.editor.state);
-        if (
-          !blockInfo.isBlockContainer ||
-          blockInfo.blockContent.node.type.spec.content !== "inline*"
-        ) {
-          return true;
-        }
+    return Object.fromEntries(
+      HEADING_LEVELS.map((level) => [
+        `Mod-Alt-${level}`,
+        () => {
+          const blockInfo = getBlockInfoFromSelection(this.editor.state);
+          if (
+            !blockInfo.isBlockContainer ||
+            blockInfo.blockContent.node.type.spec.content !== "inline*"
+          ) {
+            return true;
+          }
 
-        return this.editor.commands.command(
-          updateBlockCommand(blockInfo.bnBlock.beforePos, {
-            type: "heading",
-            props: {
-              level: 3 as any,
-            },
-          }),
-        );
-      },
-    };
+          return this.editor.commands.command(
+            updateBlockCommand(blockInfo.bnBlock.beforePos, {
+              type: "heading",
+              props: {
+                level: level as any,
+              },
+            })
+          );
+        },
+      ])
+    );
   },
   parseHTML() {
     return [
@@ -123,22 +91,11 @@ const HeadingBlockContent = createStronglyTypedTiptapNode({
         tag: "div[data-content-type=" + this.name + "]",
         contentElement: ".bn-inline-content",
       },
-      // Parse from external HTML.
-      {
-        tag: "h1",
-        attrs: { level: 1 },
+      ...HEADING_LEVELS.map((level) => ({
+        tag: `h${level}`,
+        attrs: { level },
         node: "heading",
-      },
-      {
-        tag: "h2",
-        attrs: { level: 2 },
-        node: "heading",
-      },
-      {
-        tag: "h3",
-        attrs: { level: 3 },
-        node: "heading",
-      },
+      })),
     ];
   },
 
diff --git a/packages/core/src/editor/Block.css b/packages/core/src/editor/Block.css
index 8d8437a16..e000e955b 100644
--- a/packages/core/src/editor/Block.css
+++ b/packages/core/src/editor/Block.css
@@ -134,6 +134,15 @@ NESTED BLOCKS
 [data-content-type="heading"][data-level="3"] {
   --level: 1.3em;
 }
+[data-content-type="heading"][data-level="4"] {
+  --level: 1em;
+}
+[data-content-type="heading"][data-level="5"] {
+  --level: 0.9em;
+}
+[data-content-type="heading"][data-level="6"] {
+  --level: 0.8em;
+}
 
 [data-prev-level="1"] {
   --prev-level: 3em;
@@ -144,6 +153,15 @@ NESTED BLOCKS
 [data-prev-level="3"] {
   --prev-level: 1.3em;
 }
+[data-prev-level="4"] {
+  --prev-level: 1em;
+}
+[data-prev-level="5"] {
+  --prev-level: 0.9em;
+}
+[data-prev-level="6"] {
+  --prev-level: 0.8em;
+}
 
 .bn-block-outer[data-prev-type="heading"] > .bn-block > .bn-block-content {
   font-size: var(--prev-level);
diff --git a/packages/core/src/editor/editor.css b/packages/core/src/editor/editor.css
index 3c5871b89..eb267a7b5 100644
--- a/packages/core/src/editor/editor.css
+++ b/packages/core/src/editor/editor.css
@@ -44,6 +44,9 @@ Tippy popups that are appended to document.body directly
 .bn-default-styles h1,
 .bn-default-styles h2,
 .bn-default-styles h3,
+.bn-default-styles h4,
+.bn-default-styles h5,
+.bn-default-styles h6,
 .bn-default-styles li {
   margin: 0;
   padding: 0;
diff --git a/packages/core/src/i18n/locales/ar.ts b/packages/core/src/i18n/locales/ar.ts
index 4cdaa0b47..d4b420bc3 100644
--- a/packages/core/src/i18n/locales/ar.ts
+++ b/packages/core/src/i18n/locales/ar.ts
@@ -20,6 +20,24 @@ export const ar: Dictionary = {
       aliases: ["ع3", "عنوان3", "عنوان فرعي"],
       group: "العناوين",
     },
+    heading_4: {
+      title: "عنوان 4",
+      subtext: "عنوان فرعي ثانوي صغير",
+      aliases: ["ع4", "عنوان4", "عنوان فرعي صغير"],
+      group: "العناوين",
+    },
+    heading_5: {
+      title: "عنوان 5",
+      subtext: "عنوان فرعي صغير",
+      aliases: ["ع5", "عنوان5", "عنوان فرعي صغير"],
+      group: "العناوين",
+    },
+    heading_6: {
+      title: "عنوان 6",
+      subtext: "أدنى مستوى للعناوين",
+      aliases: ["ع6", "عنوان6", "العنوان الفرعي الأدنى"],
+      group: "العناوين",
+    },
     quote: {
       title: "اقتباس",
       subtext: "اقتباس أو مقتطف",
diff --git a/packages/core/src/i18n/locales/de.ts b/packages/core/src/i18n/locales/de.ts
index d80ef907c..21784124a 100644
--- a/packages/core/src/i18n/locales/de.ts
+++ b/packages/core/src/i18n/locales/de.ts
@@ -20,6 +20,24 @@ export const de: Dictionary = {
       aliases: ["h3", "überschrift3", "unterüberschrift"],
       group: "Überschriften",
     },
+    heading_4: {
+      title: "Überschrift 4",
+      subtext: "Überschrift für kleinere Unterabschnitte",
+      aliases: ["h4", "überschrift4", "unterüberschrift4"],
+      group: "Überschriften",
+    },
+    heading_5: {
+      title: "Überschrift 5",
+      subtext: "Überschrift für tiefere Unterabschnitte",
+      aliases: ["h5", "überschrift5", "unterüberschrift5"],
+      group: "Überschriften",
+    },
+    heading_6: {
+      title: "Überschrift 6",
+      subtext: "Überschrift auf der untersten Ebene",
+      aliases: ["h6", "überschrift6", "unterüberschrift6"],
+      group: "Überschriften",
+    },
     quote: {
       title: "Zitat",
       subtext: "Zitat oder Auszug",
diff --git a/packages/core/src/i18n/locales/en.ts b/packages/core/src/i18n/locales/en.ts
index 162fbf40c..4902c8254 100644
--- a/packages/core/src/i18n/locales/en.ts
+++ b/packages/core/src/i18n/locales/en.ts
@@ -18,6 +18,24 @@ export const en = {
       aliases: ["h3", "heading3", "subheading"],
       group: "Headings",
     },
+    heading_4: {
+      title: "Heading 4",
+      subtext: "Minor subsection heading",
+      aliases: ["h4", "heading4", "subheading4"],
+      group: "Headings",
+    },
+    heading_5: {
+      title: "Heading 5",
+      subtext: "Small subsection heading",
+      aliases: ["h5", "heading5", "subheading5"],
+      group: "Headings",
+    },
+    heading_6: {
+      title: "Heading 6",
+      subtext: "Lowest-level heading",
+      aliases: ["h6", "heading6", "subheading6"],
+      group: "Headings",
+    },
     quote: {
       title: "Quote",
       subtext: "Quote or excerpt",
diff --git a/packages/core/src/i18n/locales/es.ts b/packages/core/src/i18n/locales/es.ts
index 9444beaa9..68cd4b7ac 100644
--- a/packages/core/src/i18n/locales/es.ts
+++ b/packages/core/src/i18n/locales/es.ts
@@ -20,6 +20,24 @@ export const es: Dictionary = {
       aliases: ["h3", "encabezado3", "subencabezado"],
       group: "Encabezados",
     },
+    heading_4: {
+      title: "Encabezado 4",
+      subtext: "Encabezado de subsección menor",
+      aliases: ["h4", "encabezado4", "subencabezado4"],
+      group: "Encabezados",
+    },
+    heading_5: {
+      title: "Encabezado 5",
+      subtext: "Encabezado de subsección pequeña",
+      aliases: ["h5", "encabezado5", "subencabezado5"],
+      group: "Encabezados",
+    },
+    heading_6: {
+      title: "Encabezado 6",
+      subtext: "Encabezado de nivel más bajo",
+      aliases: ["h6", "encabezado6", "subencabezado6"],
+      group: "Encabezados",
+    },
     quote: {
       title: "Cita",
       subtext: "Cita o extracto",
diff --git a/packages/core/src/i18n/locales/fr.ts b/packages/core/src/i18n/locales/fr.ts
index 3969b0e33..dad638872 100644
--- a/packages/core/src/i18n/locales/fr.ts
+++ b/packages/core/src/i18n/locales/fr.ts
@@ -21,6 +21,24 @@ export const fr: Dictionary = {
       aliases: ["h3", "titre3", "sous-titre"],
       group: "Titres",
     },
+    heading_4: {
+      title: "Titre 4",
+      subtext: "Titre de sous‑section mineure",
+      aliases: ["h4", "titre4", "sous‑titre4"],
+      group: "Titres",
+    },
+    heading_5: {
+      title: "Titre 5",
+      subtext: "Titre de sous-section mineure",
+      aliases: ["h5", "titre5", "sous-titre5"],
+      group: "Titres",
+    },
+    heading_6: {
+      title: "Titre 6",
+      subtext: "Titre de niveau le plus bas",
+      aliases: ["h6", "titre6", "sous-titre6"],
+      group: "Titres",
+    },
     quote: {
       title: "Citation",
       subtext: "Citation ou extrait",
diff --git a/packages/core/src/i18n/locales/hr.ts b/packages/core/src/i18n/locales/hr.ts
index c558d42ed..d0ad3abd9 100644
--- a/packages/core/src/i18n/locales/hr.ts
+++ b/packages/core/src/i18n/locales/hr.ts
@@ -20,6 +20,24 @@ export const hr: Dictionary = {
       aliases: ["h3", "naslov3", "podnaslov"],
       group: "Naslovi",
     },
+    heading_4: {
+      title: "Naslov 4",
+      subtext: "Manji naslov podpoglavlja",
+      aliases: ["h4", "naslov4", "podnaslov4"],
+      group: "Naslovi",
+    },
+    heading_5: {
+      title: "Naslov 5",
+      subtext: "Mali naslov podpoglavlja",
+      aliases: ["h5", "naslov5", "podnaslov5"],
+      group: "Naslovi",
+    },
+    heading_6: {
+      title: "Naslov 6",
+      subtext: "Naslov najniže razine",
+      aliases: ["h6", "naslov6", "podnaslov6"],
+      group: "Naslovi",
+    },
     quote: {
       title: "Citat",
       subtext: "Citat ili izvadak",
diff --git a/packages/core/src/i18n/locales/is.ts b/packages/core/src/i18n/locales/is.ts
index 780da27a9..13bf05d07 100644
--- a/packages/core/src/i18n/locales/is.ts
+++ b/packages/core/src/i18n/locales/is.ts
@@ -20,6 +20,24 @@ export const is: Dictionary = {
       aliases: ["h3", "fyrirsogn3", "undirfyrirsogn"],
       group: "Fyrirsagnir",
     },
+    heading_4: {
+      title: "Fyrirsögn 4",
+      subtext: "Titill fyrir minni undirhluta",
+      aliases: ["h4", "fyrirsogn4", "undirfyrirsogn4"],
+      group: "Fyrirsagnir",
+    },
+    heading_5: {
+      title: "Fyrirsögn 5",
+      subtext: "Titill fyrir litla undirkafla",
+      aliases: ["h5", "fyrirsogn5", "undirfyrirsogn5"],
+      group: "Fyrirsagnir",
+    },
+    heading_6: {
+      title: "Fyrirsögn 6",
+      subtext: "Titill á lægsta stigi",
+      aliases: ["h6", "fyrirsogn6", "undirfyrirsogn6"],
+      group: "Fyrirsagnir",
+    },
     quote: {
       title: "Tilvitnun",
       subtext: "Tilvitnun eða útdráttur",
diff --git a/packages/core/src/i18n/locales/it.ts b/packages/core/src/i18n/locales/it.ts
index c48a5e27e..25f0fc958 100644
--- a/packages/core/src/i18n/locales/it.ts
+++ b/packages/core/src/i18n/locales/it.ts
@@ -20,6 +20,24 @@ export const it: Dictionary = {
       aliases: ["h3", "intestazione3", "sottotitolo"],
       group: "Intestazioni",
     },
+    heading_4: {
+      title: "Intestazione 4",
+      subtext: "Intestazione di sottosezione minore",
+      aliases: ["h4", "intestazione4", "sottotitolo4"],
+      group: "Intestazioni",
+    },
+    heading_5: {
+      title: "Intestazione 5",
+      subtext: "Intestazione di sottosezione minore",
+      aliases: ["h5", "intestazione5", "sottotitolo5"],
+      group: "Intestazioni",
+    },
+    heading_6: {
+      title: "Intestazione 6",
+      subtext: "Intestazione di livello più basso",
+      aliases: ["h6", "intestazione6", "sottotitolo6"],
+      group: "Intestazioni",
+    },
     quote: {
       title: "Citazione",
       subtext: "Citazione o estratto",
diff --git a/packages/core/src/i18n/locales/ja.ts b/packages/core/src/i18n/locales/ja.ts
index ca6550144..d2fcddd42 100644
--- a/packages/core/src/i18n/locales/ja.ts
+++ b/packages/core/src/i18n/locales/ja.ts
@@ -20,6 +20,24 @@ export const ja: Dictionary = {
       aliases: ["h3", "見出し3", "subheading", "小見出し"],
       group: "見出し",
     },
+    heading_4: {
+      title: "見出し４",
+      subtext: "小さなサブセクションの見出しに使用",
+      aliases: ["h4", "見出し4", "subheading4", "小見出し4"],
+      group: "見出し",
+    },
+    heading_5: {
+      title: "見出し５",
+      subtext: "小さなサブセクションの見出しに使用",
+      aliases: ["h5", "見出し5", "subheading5", "小見出し5"],
+      group: "見出し",
+    },
+    heading_6: {
+      title: "見出し６",
+      subtext: "最下位レベルの見出しに使用",
+      aliases: ["h6", "見出し6", "subheading6", "小見出し6"],
+      group: "見出し",
+    },
     quote: {
       title: "引用",
       subtext: "引用または抜粋",
diff --git a/packages/core/src/i18n/locales/ko.ts b/packages/core/src/i18n/locales/ko.ts
index ffaf5ee24..877b73e1a 100644
--- a/packages/core/src/i18n/locales/ko.ts
+++ b/packages/core/src/i18n/locales/ko.ts
@@ -20,6 +20,24 @@ export const ko: Dictionary = {
       aliases: ["h3", "제목3", "subheading"],
       group: "제목",
     },
+    heading_4: {
+      title: "제목4",
+      subtext: "하위 소단락 제목",
+      aliases: ["h4", "제목4", "소제목4"],
+      group: "제목",
+    },
+    heading_5: {
+      title: "제목5",
+      subtext: "작은 하위 섹션 제목",
+      aliases: ["h5", "제목5", "소제목5"],
+      group: "제목",
+    },
+    heading_6: {
+      title: "제목6",
+      subtext: "가장 하위 수준 제목",
+      aliases: ["h6", "제목6", "소제목6"],
+      group: "제목",
+    },
     quote: {
       title: "인용",
       subtext: "인용문 또는 발췌",
diff --git a/packages/core/src/i18n/locales/nl.ts b/packages/core/src/i18n/locales/nl.ts
index 83110200e..0536bdd44 100644
--- a/packages/core/src/i18n/locales/nl.ts
+++ b/packages/core/src/i18n/locales/nl.ts
@@ -20,6 +20,24 @@ export const nl: Dictionary = {
       aliases: ["h3", "kop3", "subkop"],
       group: "Koppen",
     },
+    heading_4: {
+      title: "Kop 4",
+      subtext: "Gebruikt voor kleinere subsecties",
+      aliases: ["h4", "kop4", "subkop4"],
+      group: "Koppen",
+    },
+    heading_5: {
+      title: "Kop 5",
+      subtext: "Gebruikt voor kleinere subsecties",
+      aliases: ["h5", "kop5", "subkop5"],
+      group: "Koppen",
+    },
+    heading_6: {
+      title: "Kop 6",
+      subtext: "Gebruikt voor koppen op het laagste niveau",
+      aliases: ["h6", "kop6", "subkop6"],
+      group: "Koppen",
+    },
     quote: {
       title: "Citaat",
       subtext: "Citaat of uittreksel",
diff --git a/packages/core/src/i18n/locales/no.ts b/packages/core/src/i18n/locales/no.ts
index f8c045481..43f88b291 100644
--- a/packages/core/src/i18n/locales/no.ts
+++ b/packages/core/src/i18n/locales/no.ts
@@ -20,6 +20,24 @@ export const no: Dictionary = {
       aliases: ["h3", "overskrift3", "underoverskrift"],
       group: "Overskrifter",
     },
+    heading_4: {
+      title: "Overskrift 4",
+      subtext: "Underoverskrift for mindre underseksjoner",
+      aliases: ["h4", "overskrift4", "underoverskrift4"],
+      group: "Overskrifter",
+    },
+    heading_5: {
+      title: "Overskrift 5",
+      subtext: "Overskrift for mindre underseksjoner",
+      aliases: ["h5", "overskrift5", "underoverskrift5"],
+      group: "Overskrifter",
+    },
+    heading_6: {
+      title: "Overskrift 6",
+      subtext: "Overskrift på laveste nivå",
+      aliases: ["h6", "overskrift6", "underoverskrift6"],
+      group: "Overskrifter",
+    },
     quote: {
       title: "Sitat",
       subtext: "Sitat eller utdrag",
diff --git a/packages/core/src/i18n/locales/pl.ts b/packages/core/src/i18n/locales/pl.ts
index 43b9f9bea..9a4ae215d 100644
--- a/packages/core/src/i18n/locales/pl.ts
+++ b/packages/core/src/i18n/locales/pl.ts
@@ -20,6 +20,24 @@ export const pl: Dictionary = {
       aliases: ["h3", "naglowek3", "podnaglowek"],
       group: "Nagłówki",
     },
+    heading_4: {
+      title: "Nagłówek 4",
+      subtext: "Nagłówek mniejszej podsekcji",
+      aliases: ["h4", "naglowek4", "podnaglowek4"],
+      group: "Nagłówki",
+    },
+    heading_5: {
+      title: "Nagłówek 5",
+      subtext: "Nagłówek mniejszej podsekcji",
+      aliases: ["h5", "naglowek5", "podnaglowek5"],
+      group: "Nagłówki",
+    },
+    heading_6: {
+      title: "Nagłówek 6",
+      subtext: "Nagłówek najniższego poziomu",
+      aliases: ["h6", "naglowek6", "podnaglowek6"],
+      group: "Nagłówki",
+    },
     quote: {
       title: "Cytat",
       subtext: "Cytat lub fragment",
diff --git a/packages/core/src/i18n/locales/pt.ts b/packages/core/src/i18n/locales/pt.ts
index 88212d62f..b7ce0aaec 100644
--- a/packages/core/src/i18n/locales/pt.ts
+++ b/packages/core/src/i18n/locales/pt.ts
@@ -20,6 +20,24 @@ export const pt: Dictionary = {
       aliases: ["h3", "titulo3", "subtitulo"],
       group: "Títulos",
     },
+    heading_4: {
+      title: "Título 4",
+      subtext: "Usado para subseções menores",
+      aliases: ["h4", "titulo4", "subtitulo4"],
+      group: "Títulos",
+    },
+    heading_5: {
+      title: "Título 5",
+      subtext: "Usado para títulos de subseções pequenas",
+      aliases: ["h5", "titulo5", "subtitulo5"],
+      group: "Títulos",
+    },
+    heading_6: {
+      title: "Título 6",
+      subtext: "Usado para títulos de nível mais baixo",
+      aliases: ["h6", "titulo6", "subtitulo6"],
+      group: "Títulos",
+    },
     quote: {
       title: "Citação",
       subtext: "Citação ou trecho",
diff --git a/packages/core/src/i18n/locales/ru.ts b/packages/core/src/i18n/locales/ru.ts
index c43d766dd..a875dc9a3 100644
--- a/packages/core/src/i18n/locales/ru.ts
+++ b/packages/core/src/i18n/locales/ru.ts
@@ -20,6 +20,24 @@ export const ru: Dictionary = {
       aliases: ["h3", "heading3", "subheading", "заголовок3", "подзаголовок"],
       group: "Заголовки",
     },
+    heading_4: {
+      title: "Заголовок 4 уровня",
+      subtext: "Используется для более мелких подразделов",
+      aliases: ["h4", "heading4", "subheading4", "заголовок4", "подзаголовок4"],
+      group: "Заголовки",
+    },
+    heading_5: {
+      title: "Заголовок 5 уровня",
+      subtext: "Используется для заголовков небольших подразделов",
+      aliases: ["h5", "heading5", "subheading5", "заголовок5", "подзаголовок5"],
+      group: "Заголовки",
+    },
+    heading_6: {
+      title: "Заголовок 6 уровня",
+      subtext: "Используется для заголовков самого низкого уровня",
+      aliases: ["h6", "heading6", "subheading6", "заголовок6", "подзаголовок6"],
+      group: "Заголовки",
+    },
     quote: {
       title: "Цитата",
       subtext: "Цитата или отрывок",
diff --git a/packages/core/src/i18n/locales/uk.ts b/packages/core/src/i18n/locales/uk.ts
index 6dbb8c696..dc73c284d 100644
--- a/packages/core/src/i18n/locales/uk.ts
+++ b/packages/core/src/i18n/locales/uk.ts
@@ -20,6 +20,24 @@ export const uk: Dictionary = {
       aliases: ["h3", "heading3", "subheading", "заголовок3"],
       group: "Заголовки",
     },
+    heading_4: {
+      title: "Заголовок 4",
+      subtext: "Використовується для менших підрозділів",
+      aliases: ["h4", "heading4", "subheading4", "заголовок4"],
+      group: "Заголовки",
+    },
+    heading_5: {
+      title: "Заголовок 5",
+      subtext: "Використовується для заголовків менших підрозділів",
+      aliases: ["h5", "heading5", "subheading5", "заголовок5", "підзаголовок5"],
+      group: "Заголовки",
+    },
+    heading_6: {
+      title: "Заголовок 6",
+      subtext: "Використовується для заголовків найнижчого рівня",
+      aliases: ["h6", "heading6", "subheading6", "заголовок6", "підзаголовок6"],
+      group: "Заголовки",
+    },
     quote: {
       title: "Цитата",
       subtext: "Цитата або уривок",
diff --git a/packages/core/src/i18n/locales/vi.ts b/packages/core/src/i18n/locales/vi.ts
index 13ac0048a..94d20d8e1 100644
--- a/packages/core/src/i18n/locales/vi.ts
+++ b/packages/core/src/i18n/locales/vi.ts
@@ -20,6 +20,24 @@ export const vi: Dictionary = {
       aliases: ["h3", "tieude3", "tieudephu"],
       group: "Tiêu đề",
     },
+    heading_4: {
+      title: "Tiêu đề H4",
+      subtext: "Sử dụng cho tiêu đề phụ nhỏ hơn",
+      aliases: ["h4", "tieude4", "tieudephu4"],
+      group: "Tiêu đề",
+    },
+    heading_5: {
+      title: "Tiêu đề H5",
+      subtext: "Sử dụng cho tiêu đề phụ nhỏ hơn",
+      aliases: ["h5", "tieude5", "tieudephu5"],
+      group: "Tiêu đề",
+    },
+    heading_6: {
+      title: "Tiêu đề H6",
+      subtext: "Sử dụng cho tiêu đề cấp thấp nhất",
+      aliases: ["h6", "tieude6", "tieudephu6"],
+      group: "Tiêu đề",
+    },
     quote: {
       title: "Trích dẫn",
       subtext: "Trích dẫn hoặc đoạn trích",
diff --git a/packages/core/src/i18n/locales/zh-tw.ts b/packages/core/src/i18n/locales/zh-tw.ts
index c39906033..e1a042fad 100644
--- a/packages/core/src/i18n/locales/zh-tw.ts
+++ b/packages/core/src/i18n/locales/zh-tw.ts
@@ -20,6 +20,24 @@ export const zhTW: Dictionary = {
       aliases: ["h3", "heading3", "subheading", "標題", "三級標題"],
       group: "標題",
     },
+    heading_4: {
+      title: "四級標題",
+      subtext: "用於小節和分組標題",
+      aliases: ["h4", "heading4", "subheading", "標題", "四級標題"],
+      group: "標題",
+    },
+    heading_5: {
+      title: "五級標題",
+      subtext: "用於小節和分組標題",
+      aliases: ["h5", "heading5", "subheading", "標題", "五級標題"],
+      group: "標題",
+    },
+    heading_6: {
+      title: "六級標題",
+      subtext: "用於小節和分組標題",
+      aliases: ["h6", "heading6", "subheading", "標題", "六級標題"],
+      group: "標題",
+    },
     quote: {
       title: "引用",
       subtext: "引用或摘錄",
diff --git a/packages/core/src/i18n/locales/zh.ts b/packages/core/src/i18n/locales/zh.ts
index a7a934fd1..bffae742d 100644
--- a/packages/core/src/i18n/locales/zh.ts
+++ b/packages/core/src/i18n/locales/zh.ts
@@ -20,6 +20,24 @@ export const zh: Dictionary = {
       aliases: ["h3", "heading3", "subheading", "标题", "三级标题"],
       group: "标题",
     },
+    heading_4: {
+      title: "四级标题",
+      subtext: "用于较小的子节标题",
+      aliases: ["h4", "heading4", "subheading4", "四级标题"],
+      group: "标题",
+    },
+    heading_5: {
+      title: "五级标题",
+      subtext: "用于较小的子节标题",
+      aliases: ["h5", "heading5", "subheading5", "五级标题"],
+      group: "标题",
+    },
+    heading_6: {
+      title: "六级标题",
+      subtext: "用于最低层级的标题",
+      aliases: ["h6", "heading6", "subheading6", "六级标题"],
+      group: "标题",
+    },
     quote: {
       title: "引用",
       subtext: "引用或摘录",
diff --git a/packages/react/src/components/FormattingToolbar/DefaultSelects/BlockTypeSelect.tsx b/packages/react/src/components/FormattingToolbar/DefaultSelects/BlockTypeSelect.tsx
index 9da718425..163367ea7 100644
--- a/packages/react/src/components/FormattingToolbar/DefaultSelects/BlockTypeSelect.tsx
+++ b/packages/react/src/components/FormattingToolbar/DefaultSelects/BlockTypeSelect.tsx
@@ -11,6 +11,9 @@ import {
   RiH1,
   RiH2,
   RiH3,
+  RiH4,
+  RiH5,
+  RiH6,
   RiListCheck3,
   RiListOrdered,
   RiListUnordered,
@@ -76,6 +79,36 @@ export const blockTypeSelectItems = (
       "level" in block.props &&
       block.props.level === 3,
   },
+  {
+    name: dict.slash_menu.heading_4.title,
+    type: "heading",
+    props: { level: 4 },
+    icon: RiH4,
+    isSelected: (block) =>
+      block.type === "heading" &&
+      "level" in block.props &&
+      block.props.level === 4,
+  },
+  {
+    name: dict.slash_menu.heading_5.title,
+    type: "heading",
+    props: { level: 5 },
+    icon: RiH5,
+    isSelected: (block) =>
+      block.type === "heading" &&
+      "level" in block.props &&
+      block.props.level === 5,
+  },
+  {
+    name: dict.slash_menu.heading_6.title,
+    type: "heading",
+    props: { level: 6 },
+    icon: RiH6,
+    isSelected: (block) =>
+      block.type === "heading" &&
+      "level" in block.props &&
+      block.props.level === 6,
+  },
   {
     name: dict.slash_menu.quote.title,
     type: "quote",
diff --git a/packages/react/src/components/SuggestionMenu/getDefaultReactSlashMenuItems.tsx b/packages/react/src/components/SuggestionMenu/getDefaultReactSlashMenuItems.tsx
index 791be083a..2bd33e305 100644
--- a/packages/react/src/components/SuggestionMenu/getDefaultReactSlashMenuItems.tsx
+++ b/packages/react/src/components/SuggestionMenu/getDefaultReactSlashMenuItems.tsx
@@ -13,6 +13,9 @@ import {
   RiH1,
   RiH2,
   RiH3,
+  RiH4,
+  RiH5,
+  RiH6,
   RiImage2Fill,
   RiListCheck3,
   RiListOrdered,
@@ -30,6 +33,9 @@ const icons: Record<string, IconType> = {
   heading: RiH1,
   heading_2: RiH2,
   heading_3: RiH3,
+  heading_4: RiH4,
+  heading_5: RiH5,
+  heading_6: RiH6,
   quote: RiQuoteText,
   numbered_list: RiListOrdered,
   bullet_list: RiListUnordered,
diff --git a/packages/xl-ai/src/api/schema/__snapshots__/schemaToJSONSchema.test.ts.snap b/packages/xl-ai/src/api/schema/__snapshots__/schemaToJSONSchema.test.ts.snap
index 818662b13..361c3e4bb 100644
--- a/packages/xl-ai/src/api/schema/__snapshots__/schemaToJSONSchema.test.ts.snap
+++ b/packages/xl-ai/src/api/schema/__snapshots__/schemaToJSONSchema.test.ts.snap
@@ -45,6 +45,9 @@ exports[`creates json schema 1`] = `
                     1,
                     2,
                     3,
+                    4,
+                    5,
+                    6,
                   ],
                   "type": "number",
                 },
diff --git a/packages/xl-pdf-exporter/src/pdf/defaultSchema/blocks.tsx b/packages/xl-pdf-exporter/src/pdf/defaultSchema/blocks.tsx
index 31e4c2332..2ae9ed055 100644
--- a/packages/xl-pdf-exporter/src/pdf/defaultSchema/blocks.tsx
+++ b/packages/xl-pdf-exporter/src/pdf/defaultSchema/blocks.tsx
@@ -59,12 +59,18 @@ export const pdfBlockMappingForDefaultSchema: BlockMapping<
     );
   },
   heading: (block, exporter) => {
-    const fontSizeEM =
-      block.props.level === 1 ? 2 : block.props.level === 2 ? 1.5 : 1.17;
+    const levelFontSizeEM = {
+      1: 2,
+      2: 1.5,
+      3: 1.17,
+      4: 1,
+      5: 0.83,
+      6: 0.67,
+    }[block.props.level];
     return (
       <Text
         style={{
-          fontSize: fontSizeEM * FONT_SIZE * PIXELS_PER_POINT,
+          fontSize: levelFontSizeEM * FONT_SIZE * PIXELS_PER_POINT,
           fontWeight: 700,
         }}
       >
diff --git a/tests/src/unit/core/formatConversion/parse/__snapshots__/html/basicBlockTypes.json b/tests/src/unit/core/formatConversion/parse/__snapshots__/html/basicBlockTypes.json
index 6bc719997..4787a9ffc 100644
--- a/tests/src/unit/core/formatConversion/parse/__snapshots__/html/basicBlockTypes.json
+++ b/tests/src/unit/core/formatConversion/parse/__snapshots__/html/basicBlockTypes.json
@@ -58,11 +58,65 @@
     "content": [
       {
         "styles": {},
-        "text": "Paragraph",
+        "text": "Heading 4",
         "type": "text",
       },
     ],
     "id": "4",
+    "props": {
+      "backgroundColor": "default",
+      "level": 4,
+      "textAlignment": "left",
+      "textColor": "default",
+    },
+    "type": "heading",
+  },
+  {
+    "children": [],
+    "content": [
+      {
+        "styles": {},
+        "text": "Heading 5",
+        "type": "text",
+      },
+    ],
+    "id": "5",
+    "props": {
+      "backgroundColor": "default",
+      "level": 5,
+      "textAlignment": "left",
+      "textColor": "default",
+    },
+    "type": "heading",
+  },
+  {
+    "children": [],
+    "content": [
+      {
+        "styles": {},
+        "text": "Heading 6",
+        "type": "text",
+      },
+    ],
+    "id": "6",
+    "props": {
+      "backgroundColor": "default",
+      "level": 6,
+      "textAlignment": "left",
+      "textColor": "default",
+    },
+    "type": "heading",
+  },
+  {
+    "children": [],
+    "content": [
+      {
+        "styles": {},
+        "text": "Paragraph",
+        "type": "text",
+      },
+    ],
+    "id": "7",
     "props": {
       "backgroundColor": "default",
       "textAlignment": "left",
@@ -73,7 +127,7 @@
   {
     "children": [],
     "content": undefined,
-    "id": "5",
+    "id": "8",
     "props": {
       "backgroundColor": "default",
       "caption": "Image Caption",
@@ -131,7 +185,7 @@
         "type": "text",
       },
     ],
-    "id": "6",
+    "id": "9",
     "props": {
       "backgroundColor": "default",
       "textAlignment": "left",
diff --git a/tests/src/unit/core/formatConversion/parse/__snapshots__/html/deepNestedContent.json b/tests/src/unit/core/formatConversion/parse/__snapshots__/html/deepNestedContent.json
index 48a412514..af4b4a5bd 100644
--- a/tests/src/unit/core/formatConversion/parse/__snapshots__/html/deepNestedContent.json
+++ b/tests/src/unit/core/formatConversion/parse/__snapshots__/html/deepNestedContent.json
@@ -126,11 +126,65 @@
     "content": [
       {
         "styles": {},
-        "text": "Paragraph",
+        "text": "Heading 4",
         "type": "text",
       },
     ],
     "id": "8",
+    "props": {
+      "backgroundColor": "default",
+      "level": 4,
+      "textAlignment": "left",
+      "textColor": "default",
+    },
+    "type": "heading",
+  },
+  {
+    "children": [],
+    "content": [
+      {
+        "styles": {},
+        "text": "Heading 5",
+        "type": "text",
+      },
+    ],
+    "id": "9",
+    "props": {
+      "backgroundColor": "default",
+      "level": 5,
+      "textAlignment": "left",
+      "textColor": "default",
+    },
+    "type": "heading",
+  },
+  {
+    "children": [],
+    "content": [
+      {
+        "styles": {},
+        "text": "Heading 6",
+        "type": "text",
+      },
+    ],
+    "id": "10",
+    "props": {
+      "backgroundColor": "default",
+      "level": 6,
+      "textAlignment": "left",
+      "textColor": "default",
+    },
+    "type": "heading",
+  },
+  {
+    "children": [],
+    "content": [
+      {
+        "styles": {},
+        "text": "Paragraph",
+        "type": "text",
+      },
+    ],
+    "id": "11",
     "props": {
       "backgroundColor": "default",
       "textAlignment": "left",
@@ -141,7 +195,7 @@
   {
     "children": [],
     "content": undefined,
-    "id": "9",
+    "id": "12",
     "props": {
       "backgroundColor": "default",
       "caption": "Image Caption",
@@ -214,7 +268,7 @@
         "type": "text",
       },
     ],
-    "id": "10",
+    "id": "13",
     "props": {
       "backgroundColor": "default",
       "textAlignment": "left",
@@ -231,7 +285,7 @@
         "type": "text",
       },
     ],
-    "id": "11",
+    "id": "14",
     "props": {
       "backgroundColor": "default",
       "textAlignment": "left",
diff --git a/tests/src/unit/core/formatConversion/parse/__snapshots__/html/googleDocs.json b/tests/src/unit/core/formatConversion/parse/__snapshots__/html/googleDocs.json
index 99d97889c..91342052e 100644
--- a/tests/src/unit/core/formatConversion/parse/__snapshots__/html/googleDocs.json
+++ b/tests/src/unit/core/formatConversion/parse/__snapshots__/html/googleDocs.json
@@ -59,6 +59,66 @@
     },
     "type": "heading",
   },
+  {
+    "children": [],
+    "content": [
+      {
+        "styles": {
+          "bold": true,
+        },
+        "text": "Heading 4",
+        "type": "text",
+      },
+    ],
+    "id": "4",
+    "props": {
+      "backgroundColor": "default",
+      "level": 4,
+      "textAlignment": "left",
+      "textColor": "default",
+    },
+    "type": "heading",
+  },
+  {
+    "children": [],
+    "content": [
+      {
+        "styles": {
+          "bold": true,
+        },
+        "text": "Heading 5",
+        "type": "text",
+      },
+    ],
+    "id": "5",
+    "props": {
+      "backgroundColor": "default",
+      "level": 5,
+      "textAlignment": "left",
+      "textColor": "default",
+    },
+    "type": "heading",
+  },
+  {
+    "children": [],
+    "content": [
+      {
+        "styles": {
+          "bold": true,
+        },
+        "text": "Heading 6",
+        "type": "text",
+      },
+    ],
+    "id": "6",
+    "props": {
+      "backgroundColor": "default",
+      "level": 6,
+      "textAlignment": "left",
+      "textColor": "default",
+    },
+    "type": "heading",
+  },
   {
     "children": [],
     "content": [
@@ -68,7 +128,7 @@
         "type": "text",
       },
     ],
-    "id": "4",
+    "id": "7",
     "props": {
       "backgroundColor": "default",
       "textAlignment": "left",
@@ -85,7 +145,7 @@
         "type": "text",
       },
     ],
-    "id": "5",
+    "id": "8",
     "props": {
       "backgroundColor": "default",
       "textAlignment": "left",
@@ -102,7 +162,7 @@
         "type": "text",
       },
     ],
-    "id": "6",
+    "id": "9",
     "props": {
       "backgroundColor": "default",
       "textAlignment": "left",
@@ -120,7 +180,7 @@ Hard Break",
         "type": "text",
       },
     ],
-    "id": "7",
+    "id": "10",
     "props": {
       "backgroundColor": "default",
       "textAlignment": "left",
@@ -177,7 +237,7 @@ Hard Break",
         "type": "text",
       },
     ],
-    "id": "8",
+    "id": "11",
     "props": {
       "backgroundColor": "default",
       "textAlignment": "left",
@@ -198,7 +258,7 @@ Hard Break",
                 "type": "text",
               },
             ],
-            "id": "11",
+            "id": "14",
             "props": {
               "backgroundColor": "default",
               "textAlignment": "left",
@@ -215,7 +275,7 @@ Hard Break",
                 "type": "text",
               },
             ],
-            "id": "12",
+            "id": "15",
             "props": {
               "backgroundColor": "default",
               "textAlignment": "left",
@@ -231,7 +291,7 @@ Hard Break",
             "type": "text",
           },
         ],
-        "id": "10",
+        "id": "13",
         "props": {
           "backgroundColor": "default",
           "textAlignment": "left",
@@ -248,7 +308,7 @@ Hard Break",
             "type": "text",
           },
         ],
-        "id": "13",
+        "id": "16",
         "props": {
           "backgroundColor": "default",
           "textAlignment": "left",
@@ -264,7 +324,7 @@ Hard Break",
         "type": "text",
       },
     ],
-    "id": "9",
+    "id": "12",
     "props": {
       "backgroundColor": "default",
       "textAlignment": "left",
@@ -281,7 +341,7 @@ Hard Break",
         "type": "text",
       },
     ],
-    "id": "14",
+    "id": "17",
     "props": {
       "backgroundColor": "default",
       "textAlignment": "left",
@@ -298,7 +358,7 @@ Hard Break",
         "type": "text",
       },
     ],
-    "id": "15",
+    "id": "18",
     "props": {
       "backgroundColor": "default",
       "textAlignment": "left",
@@ -315,7 +375,7 @@ Hard Break",
         "type": "text",
       },
     ],
-    "id": "16",
+    "id": "19",
     "props": {
       "backgroundColor": "default",
       "textAlignment": "left",
@@ -326,7 +386,7 @@ Hard Break",
   {
     "children": [],
     "content": undefined,
-    "id": "17",
+    "id": "20",
     "props": {
       "backgroundColor": "default",
       "caption": "",
@@ -348,7 +408,7 @@ Hard Break",
         "type": "text",
       },
     ],
-    "id": "18",
+    "id": "21",
     "props": {
       "backgroundColor": "default",
       "textAlignment": "left",
@@ -535,7 +595,7 @@ Hard Break",
       ],
       "type": "tableContent",
     },
-    "id": "19",
+    "id": "22",
     "props": {
       "textColor": "default",
     },
@@ -550,7 +610,7 @@ Hard Break",
         "type": "text",
       },
     ],
-    "id": "20",
+    "id": "23",
     "props": {
       "backgroundColor": "default",
       "textAlignment": "left",
@@ -568,7 +628,7 @@ Hard Break",
         "type": "text",
       },
     ],
-    "id": "21",
+    "id": "24",
     "props": {
       "backgroundColor": "default",
       "textAlignment": "left",
diff --git a/tests/src/unit/core/formatConversion/parse/__snapshots__/html/notion.json b/tests/src/unit/core/formatConversion/parse/__snapshots__/html/notion.json
index b1eb97dd2..d95864ff7 100644
--- a/tests/src/unit/core/formatConversion/parse/__snapshots__/html/notion.json
+++ b/tests/src/unit/core/formatConversion/parse/__snapshots__/html/notion.json
@@ -58,11 +58,65 @@
     "content": [
       {
         "styles": {},
-        "text": "Paragraph 1",
+        "text": "Heading 4",
         "type": "text",
       },
     ],
     "id": "4",
+    "props": {
+      "backgroundColor": "default",
+      "level": 4,
+      "textAlignment": "left",
+      "textColor": "default",
+    },
+    "type": "heading",
+  },
+  {
+    "children": [],
+    "content": [
+      {
+        "styles": {},
+        "text": "Heading 5",
+        "type": "text",
+      },
+    ],
+    "id": "5",
+    "props": {
+      "backgroundColor": "default",
+      "level": 5,
+      "textAlignment": "left",
+      "textColor": "default",
+    },
+    "type": "heading",
+  },
+  {
+    "children": [],
+    "content": [
+      {
+        "styles": {},
+        "text": "Heading 6",
+        "type": "text",
+      },
+    ],
+    "id": "6",
+    "props": {
+      "backgroundColor": "default",
+      "level": 6,
+      "textAlignment": "left",
+      "textColor": "default",
+    },
+    "type": "heading",
+  },
+  {
+    "children": [],
+    "content": [
+      {
+        "styles": {},
+        "text": "Paragraph 1",
+        "type": "text",
+      },
+    ],
+    "id": "7",
     "props": {
       "backgroundColor": "default",
       "textAlignment": "left",
@@ -79,7 +133,7 @@
         "type": "text",
       },
     ],
-    "id": "5",
+    "id": "8",
     "props": {
       "backgroundColor": "default",
       "textAlignment": "left",
@@ -96,7 +150,7 @@
         "type": "text",
       },
     ],
-    "id": "6",
+    "id": "9",
     "props": {
       "backgroundColor": "default",
       "textAlignment": "left",
@@ -113,7 +167,7 @@
         "type": "text",
       },
     ],
-    "id": "7",
+    "id": "10",
     "props": {
       "backgroundColor": "default",
       "textAlignment": "left",
@@ -170,7 +224,7 @@
         "type": "text",
       },
     ],
-    "id": "8",
+    "id": "11",
     "props": {
       "backgroundColor": "default",
       "textAlignment": "left",
@@ -191,7 +245,7 @@
                 "type": "text",
               },
             ],
-            "id": "11",
+            "id": "14",
             "props": {
               "backgroundColor": "default",
               "textAlignment": "left",
@@ -208,7 +262,7 @@
                 "type": "text",
               },
             ],
-            "id": "12",
+            "id": "15",
             "props": {
               "backgroundColor": "default",
               "textAlignment": "left",
@@ -224,7 +278,7 @@
             "type": "text",
           },
         ],
-        "id": "10",
+        "id": "13",
         "props": {
           "backgroundColor": "default",
           "textAlignment": "left",
@@ -241,7 +295,7 @@
             "type": "text",
           },
         ],
-        "id": "13",
+        "id": "16",
         "props": {
           "backgroundColor": "default",
           "textAlignment": "left",
@@ -257,7 +311,7 @@
         "type": "text",
       },
     ],
-    "id": "9",
+    "id": "12",
     "props": {
       "backgroundColor": "default",
       "textAlignment": "left",
@@ -274,7 +328,7 @@
         "type": "text",
       },
     ],
-    "id": "14",
+    "id": "17",
     "props": {
       "backgroundColor": "default",
       "textAlignment": "left",
@@ -291,7 +345,7 @@
         "type": "text",
       },
     ],
-    "id": "15",
+    "id": "18",
     "props": {
       "backgroundColor": "default",
       "textAlignment": "left",
@@ -308,7 +362,7 @@
         "type": "text",
       },
     ],
-    "id": "16",
+    "id": "19",
     "props": {
       "backgroundColor": "default",
       "textAlignment": "left",
@@ -325,7 +379,7 @@
         "type": "text",
       },
     ],
-    "id": "17",
+    "id": "20",
     "props": {
       "backgroundColor": "default",
       "textAlignment": "left",
@@ -353,7 +407,7 @@
         "type": "link",
       },
     ],
-    "id": "18",
+    "id": "21",
     "props": {
       "backgroundColor": "default",
       "textAlignment": "left",
@@ -540,7 +594,7 @@
       ],
       "type": "tableContent",
     },
-    "id": "19",
+    "id": "22",
     "props": {
       "textColor": "default",
     },
@@ -555,7 +609,7 @@
         "type": "text",
       },
     ],
-    "id": "20",
+    "id": "23",
     "props": {
       "backgroundColor": "default",
       "textAlignment": "left",
diff --git a/tests/src/unit/core/formatConversion/parse/__snapshots__/markdown/complex.json b/tests/src/unit/core/formatConversion/parse/__snapshots__/markdown/complex.json
index 81ac21d79..08b5c1208 100644
--- a/tests/src/unit/core/formatConversion/parse/__snapshots__/markdown/complex.json
+++ b/tests/src/unit/core/formatConversion/parse/__snapshots__/markdown/complex.json
@@ -58,11 +58,65 @@
     "content": [
       {
         "styles": {},
-        "text": "Paragraph",
+        "text": "Heading 4",
         "type": "text",
       },
     ],
     "id": "4",
+    "props": {
+      "backgroundColor": "default",
+      "level": 4,
+      "textAlignment": "left",
+      "textColor": "default",
+    },
+    "type": "heading",
+  },
+  {
+    "children": [],
+    "content": [
+      {
+        "styles": {},
+        "text": "Heading 5",
+        "type": "text",
+      },
+    ],
+    "id": "5",
+    "props": {
+      "backgroundColor": "default",
+      "level": 5,
+      "textAlignment": "left",
+      "textColor": "default",
+    },
+    "type": "heading",
+  },
+  {
+    "children": [],
+    "content": [
+      {
+        "styles": {},
+        "text": "Heading 6",
+        "type": "text",
+      },
+    ],
+    "id": "6",
+    "props": {
+      "backgroundColor": "default",
+      "level": 6,
+      "textAlignment": "left",
+      "textColor": "default",
+    },
+    "type": "heading",
+  },
+  {
+    "children": [],
+    "content": [
+      {
+        "styles": {},
+        "text": "Paragraph",
+        "type": "text",
+      },
+    ],
+    "id": "7",
     "props": {
       "backgroundColor": "default",
       "textAlignment": "left",
@@ -98,7 +152,7 @@
         "type": "text",
       },
     ],
-    "id": "5",
+    "id": "8",
     "props": {
       "backgroundColor": "default",
       "textAlignment": "left",
@@ -134,7 +188,7 @@
         "type": "text",
       },
     ],
-    "id": "6",
+    "id": "9",
     "props": {
       "backgroundColor": "default",
       "textAlignment": "left",
@@ -151,7 +205,7 @@
         "type": "text",
       },
     ],
-    "id": "7",
+    "id": "10",
     "props": {
       "backgroundColor": "default",
       "textAlignment": "left",
@@ -172,7 +226,7 @@
                 "type": "text",
               },
             ],
-            "id": "10",
+            "id": "13",
             "props": {
               "backgroundColor": "default",
               "textAlignment": "left",
@@ -188,7 +242,7 @@
             "type": "text",
           },
         ],
-        "id": "9",
+        "id": "12",
         "props": {
           "backgroundColor": "default",
           "textAlignment": "left",
@@ -207,7 +261,7 @@
                 "type": "text",
               },
             ],
-            "id": "12",
+            "id": "15",
             "props": {
               "backgroundColor": "default",
               "textAlignment": "left",
@@ -224,7 +278,7 @@
                 "type": "text",
               },
             ],
-            "id": "13",
+            "id": "16",
             "props": {
               "backgroundColor": "default",
               "textAlignment": "left",
@@ -243,7 +297,7 @@
                     "type": "text",
                   },
                 ],
-                "id": "15",
+                "id": "18",
                 "props": {
                   "backgroundColor": "default",
                   "textAlignment": "left",
@@ -259,7 +313,7 @@
                 "type": "text",
               },
             ],
-            "id": "14",
+            "id": "17",
             "props": {
               "backgroundColor": "default",
               "textAlignment": "left",
@@ -276,7 +330,7 @@
                 "type": "text",
               },
             ],
-            "id": "16",
+            "id": "19",
             "props": {
               "backgroundColor": "default",
               "textAlignment": "left",
@@ -292,7 +346,7 @@
             "type": "text",
           },
         ],
-        "id": "11",
+        "id": "14",
         "props": {
           "backgroundColor": "default",
           "textAlignment": "left",
@@ -309,7 +363,7 @@
             "type": "text",
           },
         ],
-        "id": "17",
+        "id": "20",
         "props": {
           "backgroundColor": "default",
           "textAlignment": "left",
@@ -325,7 +379,7 @@
         "type": "text",
       },
     ],
-    "id": "8",
+    "id": "11",
     "props": {
       "backgroundColor": "default",
       "textAlignment": "left",
@@ -342,7 +396,7 @@
         "type": "text",
       },
     ],
-    "id": "18",
+    "id": "21",
     "props": {
       "backgroundColor": "default",
       "textAlignment": "left",
diff --git a/tests/src/unit/core/formatConversion/parse/parseTestInstances.ts b/tests/src/unit/core/formatConversion/parse/parseTestInstances.ts
index db65f162f..24691a394 100644
--- a/tests/src/unit/core/formatConversion/parse/parseTestInstances.ts
+++ b/tests/src/unit/core/formatConversion/parse/parseTestInstances.ts
@@ -22,6 +22,9 @@ export const parseTestInstancesHTML: TestInstance<
       content: `<h1>Heading 1</h1>
 <h2>Heading 2</h2>
 <h3>Heading 3</h3>
+<h4>Heading 4</h4>
+<h5>Heading 5</h5>
+<h6>Heading 6</h6>
 <p>Paragraph</p>
 <figure><img src="exampleURL" /><figcaption>Image Caption</figcaption></figure>
 <p>None <strong>Bold </strong><em>Italic </em><u>Underline </u><s>Strikethrough </s><strong><em><s><u>All</u></s></em></strong></p>`,
@@ -576,6 +579,9 @@ export const parseTestInstancesHTML: TestInstance<
         <h1>Heading 1</h1>
         <h2>Heading 2</h2>
         <h3>Heading 3</h3>
+        <h4>Heading 4</h4>
+        <h5>Heading 5</h5>
+        <h6>Heading 6</h6>
         <p>Paragraph</p>
         <figure><img src="exampleURL"><figcaption>Image Caption</figcaption></figure>
         <p><strong>Bold</strong> <em>Italic</em> <u>Underline</u> <s>Strikethrough</s> <strong><em><s><u>All</u></s></em></strong></p>
@@ -642,6 +648,9 @@ export const parseTestInstancesHTML: TestInstance<
       content: `<meta charset='utf-8'><h1>Heading 1</h1>
 <h2>Heading 2</h2>
 <h3>Heading 3</h3>
+<h4>Heading 4</h4>
+<h5>Heading 5</h5>
+<h6>Heading 6</h6>
 <p>Paragraph 1</p>
 <p>Nested Paragraph 1</p>
 <p>Nested Paragraph 2</p>
@@ -703,6 +712,9 @@ With Hard Break</p>
 <h1 dir="ltr" style="line-height:1.38;margin-left: 18pt;text-indent: -18pt;margin-top:24pt;margin-bottom:6pt;padding:0pt 0pt 0pt 18pt;"><span style="font-size:23pt;font-family:Arial,sans-serif;color:#000000;background-color:transparent;font-weight:700;font-style:normal;font-variant:normal;text-decoration:none;vertical-align:baseline;white-space:pre;white-space:pre-wrap;">Heading 1</span></h1>
 <h2 dir="ltr" style="line-height:1.38;margin-left: 18pt;text-indent: -18pt;margin-top:18pt;margin-bottom:4pt;padding:0pt 0pt 0pt 18pt;"><span style="font-size:17pt;font-family:Arial,sans-serif;color:#000000;background-color:transparent;font-weight:700;font-style:normal;font-variant:normal;text-decoration:none;vertical-align:baseline;white-space:pre;white-space:pre-wrap;">Heading 2</span></h2>
 <h3 dir="ltr" style="line-height:1.38;margin-left: 18pt;text-indent: -18pt;margin-top:14pt;margin-bottom:4pt;padding:0pt 0pt 0pt 18pt;"><span style="font-size:13pt;font-family:Arial,sans-serif;color:#000000;background-color:transparent;font-weight:700;font-style:normal;font-variant:normal;text-decoration:none;vertical-align:baseline;white-space:pre;white-space:pre-wrap;">Heading 3</span></h3>
+<h4 dir="ltr" style="line-height:1.38;margin-left: 18pt;text-indent: -18pt;margin-top:14pt;margin-bottom:4pt;padding:0pt 0pt 0pt 18pt;"><span style="font-size:13pt;font-family:Arial,sans-serif;color:#000000;background-color:transparent;font-weight:700;font-style:normal;font-variant:normal;text-decoration:none;vertical-align:baseline;white-space:pre;white-space:pre-wrap;">Heading 4</span></h4>
+<h5 dir="ltr" style="line-height:1.38;margin-left: 18pt;text-indent: -18pt;margin-top:14pt;margin-bottom:4pt;padding:0pt 0pt 0pt 18pt;"><span style="font-size:13pt;font-family:Arial,sans-serif;color:#000000;background-color:transparent;font-weight:700;font-style:normal;font-variant:normal;text-decoration:none;vertical-align:baseline;white-space:pre;white-space:pre-wrap;">Heading 5</span></h5>
+<h6 dir="ltr" style="line-height:1.38;margin-left: 18pt;text-indent: -18pt;margin-top:14pt;margin-bottom:4pt;padding:0pt 0pt 0pt 18pt;"><span style="font-size:13pt;font-family:Arial,sans-serif;color:#000000;background-color:transparent;font-weight:700;font-style:normal;font-variant:normal;text-decoration:none;vertical-align:baseline;white-space:pre;white-space:pre-wrap;">Heading 6</span></h6>
 <p dir="ltr" style="line-height:1.38;margin-top:12pt;margin-bottom:12pt;"><span style="font-size:11pt;font-family:Arial,sans-serif;color:#000000;background-color:transparent;font-weight:400;font-style:normal;font-variant:normal;text-decoration:none;vertical-align:baseline;white-space:pre;white-space:pre-wrap;">Paragraph 1</span></p>
 <p dir="ltr" style="line-height:1.38;margin-top:12pt;margin-bottom:12pt;"><span style="font-size:11pt;font-family:Arial,sans-serif;color:#000000;background-color:transparent;font-weight:400;font-style:normal;font-variant:normal;text-decoration:none;vertical-align:baseline;white-space:pre;white-space:pre-wrap;">Paragraph 2</span></p>
 <p dir="ltr" style="line-height:1.38;margin-top:12pt;margin-bottom:12pt;"><span style="font-size:11pt;font-family:Arial,sans-serif;color:#000000;background-color:transparent;font-weight:400;font-style:normal;font-variant:normal;text-decoration:none;vertical-align:baseline;white-space:pre;white-space:pre-wrap;">Paragraph 3</span></p>
@@ -854,6 +866,12 @@ Paragraph
 
 ### Heading 3
 
+#### Heading 4
+
+##### Heading 5
+
+###### Heading 6
+
 Paragraph
 
 P**ara***grap*h