diff --git a/.github/workflows/luacheck.yml b/.github/workflows/luacheck.yml
new file mode 100644
index 000000000000..83f552b94806
--- /dev/null
+++ b/.github/workflows/luacheck.yml
@@ -0,0 +1,13 @@
+name: Luacheck
+
+on: [ push, pull_request ]
+
+jobs:
+
+  luacheck:
+    runs-on: ubuntu-22.04
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+      - name: Luacheck
+        uses: lunarmodules/luacheck@v1
diff --git a/.luacheckrc b/.luacheckrc
new file mode 100644
index 000000000000..fe49afb937d0
--- /dev/null
+++ b/.luacheckrc
@@ -0,0 +1,27 @@
+std = "lua54"
+
+max_line_length = false
+
+files["**/test/lua/**"] = {
+  std = "+pandoc_filter"
+}
+
+files["**/test/*.lua"] = {
+  std = "+pandoc_custom"
+}
+
+files["data/**"] = {
+  std = "+pandoc_custom"
+}
+
+files["tools/**"] = {
+  std = "+pandoc_custom"
+}
+
+files["man/**"] = {
+  std = "+pandoc_script"
+}
+
+exclude_files = {
+  ".stack-work"
+}
diff --git a/data/creole.lua b/data/creole.lua
index 590dfc87179d..9084cb5efe40 100644
--- a/data/creole.lua
+++ b/data/creole.lua
@@ -2,9 +2,7 @@
 -- http://www.wikicreole.org/wiki/CheatSheet
 
 -- For better performance we put these functions in local variables:
-local P, S, R, Cf, Cc, Ct, V, Cs, Cg, Cb, B, C, Cmt =
-  lpeg.P, lpeg.S, lpeg.R, lpeg.Cf, lpeg.Cc, lpeg.Ct, lpeg.V,
-  lpeg.Cs, lpeg.Cg, lpeg.Cb, lpeg.B, lpeg.C, lpeg.Cmt
+local P, S, Cc, Ct, V, C = lpeg.P, lpeg.S, lpeg.Cc, lpeg.Ct, lpeg.V, lpeg.C
 
 local whitespacechar = S(" \t\r\n")
 local specialchar = S("/*~[]\\{}|")
@@ -52,7 +50,7 @@ local function ListItem(lev, ch)
 end
 
 -- Grammar
-G = P{ "Doc",
+local grammar = P{ "Doc",
   Doc = Ct(V"Block"^0)
       / pandoc.Pandoc ;
   Block = blankline^0
@@ -185,6 +183,6 @@ G = P{ "Doc",
          / pandoc.Strong ;
 }
 
-function Reader(input, reader_options)
-  return lpeg.match(G, tostring(input))
+function Reader(input, _reader_options)
+  return lpeg.match(grammar, tostring(input))
 end
diff --git a/man/manfilter.lua b/man/manfilter.lua
index 6abd950fc7e1..b7797feb305c 100644
--- a/man/manfilter.lua
+++ b/man/manfilter.lua
@@ -5,8 +5,8 @@ local text = require('text')
 function Header(el)
     if el.level == 1 then
       return pandoc.walk_block(el, {
-        Str = function(el)
-            return pandoc.Str(text.upper(el.text))
+        Str = function(str_el)
+            return pandoc.Str(text.upper(str_el.text))
         end })
     end
 end
@@ -17,11 +17,11 @@ function Table(el)
   local rendered = pandoc.write(pandoc.Pandoc({el}), "plain")
   local adjusted = rendered  -- tame grid table lines
                      :gsub("%+([=:][=:]+)",
-                       function(s)
-                         return " " .. string.rep("-", #s - 1)
+                       function(str)
+                         return " " .. string.rep("-", #str - 1)
                        end)
                      :gsub("(%+[-:][-:]+)",
-                       function(s)
+                       function(_str)
                          return ""
                        end)
                      :gsub("%+\n","\n")
@@ -39,6 +39,6 @@ function Link(el)
 end
 
 -- remove notes
-function Note(el)
+function Note(_el)
     return {}
 end
diff --git a/pandoc-lua-engine/test/bytestring-reader.lua b/pandoc-lua-engine/test/bytestring-reader.lua
index 7908479ecb75..27ed0a8bbcd0 100644
--- a/pandoc-lua-engine/test/bytestring-reader.lua
+++ b/pandoc-lua-engine/test/bytestring-reader.lua
@@ -1,4 +1,4 @@
-function ByteStringReader (input, opts)
+function ByteStringReader (input, _opts)
   local chars = pandoc.List{}
   for i = 1, #input do
     chars:insert(utf8.char(input:byte(i,i)))
diff --git a/pandoc-lua-engine/test/bytestring.lua b/pandoc-lua-engine/test/bytestring.lua
index f872e28d497d..4499e8e839ab 100644
--- a/pandoc-lua-engine/test/bytestring.lua
+++ b/pandoc-lua-engine/test/bytestring.lua
@@ -1,4 +1,4 @@
-function ByteStringWriter (doc, opts)
+function ByteStringWriter (_doc, _opts)
   local buffer = {}
   for i=0, 255 do
     table.insert(buffer, string.char(i))
diff --git a/pandoc-lua-engine/test/extensions.lua b/pandoc-lua-engine/test/extensions.lua
index d286f5c416b0..538f5ede042d 100644
--- a/pandoc-lua-engine/test/extensions.lua
+++ b/pandoc-lua-engine/test/extensions.lua
@@ -1,4 +1,4 @@
-function Writer (doc, opts)
+function Writer (_doc, opts)
   local output = 'smart extension is %s;\ncitations extension is %s\n'
   local status = function (ext)
     return opts.extensions:includes(ext) and 'enabled' or 'disabled'
diff --git a/pandoc-lua-engine/test/lua/block-count.lua b/pandoc-lua-engine/test/lua/block-count.lua
index 508b05ea8733..0a54e45df878 100644
--- a/pandoc-lua-engine/test/lua/block-count.lua
+++ b/pandoc-lua-engine/test/lua/block-count.lua
@@ -1,10 +1,10 @@
 local num_blocks = 0
 
-function Block(el)
+function Block(_el)
   num_blocks = num_blocks + 1
 end
 
-function Pandoc(blocks, meta)
+function Pandoc(_blocks, _meta)
   return pandoc.Pandoc {
     pandoc.Para{pandoc.Str(num_blocks)}
   }
diff --git a/pandoc-lua-engine/test/lua/hello-world-doc.lua b/pandoc-lua-engine/test/lua/hello-world-doc.lua
index 62236584e6b7..890d320ffa5e 100644
--- a/pandoc-lua-engine/test/lua/hello-world-doc.lua
+++ b/pandoc-lua-engine/test/lua/hello-world-doc.lua
@@ -1,6 +1,6 @@
 return {
   {
-    Pandoc = function(doc)
+    Pandoc = function(_doc)
       local meta = {}
       local hello = { pandoc.Str "Hello,", pandoc.Space(), pandoc.Str "World!" }
       local blocks = { pandoc.Para(hello) }
diff --git a/pandoc-lua-engine/test/lua/implicit-doc-filter.lua b/pandoc-lua-engine/test/lua/implicit-doc-filter.lua
index f053dc1b2483..6ae03d898945 100644
--- a/pandoc-lua-engine/test/lua/implicit-doc-filter.lua
+++ b/pandoc-lua-engine/test/lua/implicit-doc-filter.lua
@@ -1,4 +1,4 @@
-function Pandoc (doc)
+function Pandoc (_doc)
   local meta = {}
   local hello = { pandoc.Str "Hello,", pandoc.Space(), pandoc.Str "World!" }
   local blocks = { pandoc.Para(hello) }
diff --git a/pandoc-lua-engine/test/lua/inlines-filter.lua b/pandoc-lua-engine/test/lua/inlines-filter.lua
index 69608bd77a34..54a76fa82c88 100644
--- a/pandoc-lua-engine/test/lua/inlines-filter.lua
+++ b/pandoc-lua-engine/test/lua/inlines-filter.lua
@@ -1,4 +1,4 @@
-function isWorldAfterSpace (fst, snd)
+local function isWorldAfterSpace (fst, snd)
   return fst and fst.t == 'LineBreak'
    and snd and snd.t == 'Str' and snd.text == 'World!'
 end
diff --git a/pandoc-lua-engine/test/lua/metatable-catch-all.lua b/pandoc-lua-engine/test/lua/metatable-catch-all.lua
index 05df16bbf875..f36fad7a772f 100644
--- a/pandoc-lua-engine/test/lua/metatable-catch-all.lua
+++ b/pandoc-lua-engine/test/lua/metatable-catch-all.lua
@@ -1,12 +1,12 @@
 local num_inlines = 0
 
-function catch_all(el)
+local function catch_all(el)
   if el.tag and pandoc.Inline.constructor[el.tag] then
     num_inlines = num_inlines + 1
   end
 end
 
-function Pandoc(blocks, meta)
+function Pandoc(_blocks, _meta)
   return pandoc.Pandoc {
     pandoc.Para{pandoc.Str(num_inlines)}
   }
diff --git a/pandoc-lua-engine/test/lua/module/pandoc-list.lua b/pandoc-lua-engine/test/lua/module/pandoc-list.lua
index 27790ce96cee..de1da8117284 100644
--- a/pandoc-lua-engine/test/lua/module/pandoc-list.lua
+++ b/pandoc-lua-engine/test/lua/module/pandoc-list.lua
@@ -7,7 +7,7 @@ local group = tasty.test_group
 
 return {
   group 'List as function' {
-    test('equivalent to List:new', function (x)
+    test('equivalent to List:new', function ()
       local new = List:new {'ramen'}
       local list = List {'ramen'}
       assert.are_same(new, list)
@@ -109,25 +109,25 @@ return {
     end),
     test('leaves original list unchanged', function ()
       local primes = List:new {2, 3, 5, 7}
-      local squares = primes:map(function (x) return x^2 end)
+      local _ = primes:map(function (x) return x^2 end)
       assert.are_same({2, 3, 5, 7}, primes)
     end)
   },
 
   group 'new' {
     test('make table usable as list', function ()
-      local test = List:new{1, 1, 2, 3, 5}
+      local out = List:new{1, 1, 2, 3, 5}
       assert.are_same(
         {1, 1, 4, 9, 25},
-        test:map(function (x) return x^2 end)
+        out:map(function (x) return x^2 end)
       )
     end),
     test('return empty list if no argument is given', function ()
        assert.are_same({}, List:new())
     end),
     test('metatable of result is pandoc.List', function ()
-      local test = List:new{5}
-      assert.are_equal(List, getmetatable(test))
+      local out = List:new{5}
+      assert.are_equal(List, getmetatable(out))
     end)
   },
 
diff --git a/pandoc-lua-engine/test/lua/module/pandoc-structure.lua b/pandoc-lua-engine/test/lua/module/pandoc-structure.lua
index af19785c92a5..bc3b661e2491 100644
--- a/pandoc-lua-engine/test/lua/module/pandoc-structure.lua
+++ b/pandoc-lua-engine/test/lua/module/pandoc-structure.lua
@@ -1,7 +1,5 @@
 local tasty = require 'tasty'
 local structure = require 'pandoc.structure'
-local path = require 'pandoc.path'
-local system = require 'pandoc.system'
 
 local assert = tasty.assert
 local test = tasty.test_case
diff --git a/pandoc-lua-engine/test/lua/module/pandoc-template.lua b/pandoc-lua-engine/test/lua/module/pandoc-template.lua
index 65e0798f5c38..8e32e072badc 100644
--- a/pandoc-lua-engine/test/lua/module/pandoc-template.lua
+++ b/pandoc-lua-engine/test/lua/module/pandoc-template.lua
@@ -25,7 +25,7 @@ return {
       )
     end),
     test('fails on unknown format', function ()
-           local success, msg = pcall(function ()
+           local success, _ = pcall(function ()
                return pandoc.utils.type(template.default 'nosuchformat')
            end)
            assert.is_falsy(success)
@@ -42,7 +42,7 @@ return {
       )
     end),
     test('fails on non-existent file', function ()
-      local success, msg = pcall(function ()
+      local success, _ = pcall(function ()
         return pandoc.utils.type(template.get 'nosuchfile.nope')
       end)
       assert.is_falsy(success)
diff --git a/pandoc-lua-engine/test/lua/module/pandoc-utils.lua b/pandoc-lua-engine/test/lua/module/pandoc-utils.lua
index 573a5987ae5d..2c6f20da4c00 100644
--- a/pandoc-lua-engine/test/lua/module/pandoc-utils.lua
+++ b/pandoc-lua-engine/test/lua/module/pandoc-utils.lua
@@ -149,6 +149,7 @@ return {
     test("doesn't change the local environment by default", function ()
       pandoc.system.with_temporary_directory('lua-filter', function (dir)
         local filter_path = pandoc.path.join{dir, 'test.lua'}
+        -- luacheck: ignore foo
         local foo
         local filter = 'foo = 42'
         local fh = io.open(filter_path, 'wb')
@@ -284,7 +285,7 @@ return {
 
   group 'to_simple_table' {
     test('convertes Table', function ()
-      function simple_cell (blocks)
+      local function simple_cell (blocks)
         return {
           attr = pandoc.Attr(),
           alignment = "AlignDefault",
diff --git a/pandoc-lua-engine/test/lua/module/pandoc.lua b/pandoc-lua-engine/test/lua/module/pandoc.lua
index 5df547d2420e..99fee675a400 100644
--- a/pandoc-lua-engine/test/lua/module/pandoc.lua
+++ b/pandoc-lua-engine/test/lua/module/pandoc.lua
@@ -4,7 +4,7 @@ local test = tasty.test_case
 local group = tasty.test_group
 local assert = tasty.assert
 
-function os_is_windows ()
+local function os_is_windows ()
   return package.config:sub(1,1) == '\\'
 end
 
diff --git a/pandoc-lua-engine/test/sample.lua b/pandoc-lua-engine/test/sample.lua
index 0294cfbaf899..8e61e488bf1d 100644
--- a/pandoc-lua-engine/test/sample.lua
+++ b/pandoc-lua-engine/test/sample.lua
@@ -21,7 +21,6 @@ function Writer (doc, opts)
 end
 
 local pipe = pandoc.pipe
-local stringify = (require 'pandoc.utils').stringify
 
 -- Choose the image format based on the value of the
 -- `image_format` environment variable.
@@ -80,7 +79,7 @@ end
 -- This gives you a fragment.  You could use the metadata table to
 -- fill variables in a custom lua template.  Or, pass `--template=...`
 -- to pandoc, and pandoc will do the template processing as usual.
-function Doc(body, metadata, variables)
+function Doc(body, _metadata, _variables)
   local buffer = {}
   local function add(s)
     table.insert(buffer, s)
@@ -146,7 +145,7 @@ function Link(s, tgt, tit, attr)
          escape(tit,true) .. '"' .. attributes(attr) .. '>' .. s .. '</a>'
 end
 
-function Image(s, src, tit, attr)
+function Image(_s, src, tit, _attr)
   return '<img src="' .. escape(src,true) .. '" title="' ..
          escape(tit,true) .. '"/>'
 end
@@ -283,7 +282,7 @@ local function html_align(align)
   end
 end
 
-function CaptionedImage(src, tit, caption, attr)
+function CaptionedImage(src, _tit, caption, attr)
   if #caption == 0 then
     return '<p><img src="' .. escape(src,true) .. '" id="' .. attr.id ..
       '"/></p>'
diff --git a/tools/extract-changes.lua b/tools/extract-changes.lua
index 5d19c8d03ac6..8702c3356bc6 100644
--- a/tools/extract-changes.lua
+++ b/tools/extract-changes.lua
@@ -2,7 +2,7 @@
 
 function Pandoc(el)
   local newblocks = {}
-  i = 1
+  local i = 1
   while i <= #el.blocks and
       not (el.blocks[i].t == "Header" and el.blocks[i].level == 2) do
     i = i+1
diff --git a/tools/moduledeps.lua b/tools/moduledeps.lua
index 038eb5cc490f..af9c1e4416f5 100644
--- a/tools/moduledeps.lua
+++ b/tools/moduledeps.lua
@@ -14,12 +14,12 @@ end
 
 if not (mode == "tree" or mode == "transitive") then
   io.write("Usage: lua moduledeps (tree|transitive) modulename\n")
-  io.exit(1)
+  os.exit(1)
 end
 
 if #roots == 0 then
   io.write("Usage: lua moduledeps modulename+\n")
-  io.exit(1)
+  os.exit(1)
 end
 
 for line in lines do
@@ -35,11 +35,11 @@ end
 
 local transitive = {}
 
-function prind(ind, s)
+local function prind(ind, s)
   io.write(string.rep(" ",ind) .. s .. "\n")
 end
 
-function add_transitive_deps(mod)
+local function add_transitive_deps(mod)
   if transitive[mod] then
     return
   end
@@ -53,7 +53,7 @@ function add_transitive_deps(mod)
   end
 end
 
-function print_direct_deps(mod, ind)
+local function print_direct_deps(mod, ind)
   ind = ind or 0
   prind(ind, mod)
   for dep,_ in pairs(dependencies[mod]) do
diff --git a/tools/update-lua-module-docs.lua b/tools/update-lua-module-docs.lua
index 1491cc7dd9bc..fac0d5a21ae1 100644
--- a/tools/update-lua-module-docs.lua
+++ b/tools/update-lua-module-docs.lua
@@ -264,10 +264,9 @@ local function render_type (name, level, modulename)
   local properties = Blocks{}
   if next(metatable.docs.properties) then
     local propattr = {'type-' .. id .. '-properties'}
-    local attr
     properties:insert(Header(level + 1, "Properties", propattr))
     for propname, prop in sorted(metatable.docs.properties) do
-      attr = {'type-' .. nameprefix .. '.' .. name .. '.' .. propname}
+      local attr = {'type-' .. nameprefix .. '.' .. name .. '.' .. propname}
       properties:insert(Header(level + 2, propname, attr))
       properties:insert(
         Plain(read_inlines(prop.description) ..
@@ -280,9 +279,10 @@ local function render_type (name, level, modulename)
   if next(metatable.methods) then
     local attr = {'type-' .. id .. '-methods'}
     methods:insert(Header(level + 1, "Methods", attr))
-    for _, method in sorted(metatable.methods) do
-      -- attr = {'type-' .. modulename .. '.' .. name .. '.' .. name}
-      -- methods:insert(Header(level + 2, name, attr))
+    -- luacheck: ignore propname
+    for propname, method in sorted(metatable.methods) do
+      -- attr = {'type-' .. modulename .. '.' .. name .. '.' .. propname}
+      -- methods:insert(Header(level + 2, propname, attr))
       methods:extend(render_function(documentation(method), level+2, id))
     end
   end
@@ -342,12 +342,11 @@ end
 local function render_main_pandoc_module (doc)
   local constants_section = Blocks{Header(2, "Constants")}
   local fields = List{}
-  for i, field in ipairs(doc.fields) do
+  for _, field in ipairs(doc.fields) do
     if tostring(field.type) == 'string' then
       constants_section:extend(render_field(field, 2, "pandoc"))
-    elseif field.name:match '^[A-Z]' then
-      -- Ignore (these are the `Block` and `Inline` tables)
-    else
+    -- Ignore (these are the `Block` and `Inline` tables)
+    elseif not field.name:match '^[A-Z]' then
       fields:insert(field)
     end
   end
diff --git a/tools/update-readme.lua b/tools/update-readme.lua
index 38662d6277fc..3130b58d54e9 100644
--- a/tools/update-readme.lua
+++ b/tools/update-readme.lua
@@ -3,9 +3,9 @@
 
 local f = assert(io.open("MANUAL.txt", "r"))
 local manual = f:read("*all")
-mdoc = pandoc.read(manual, "markdown")
+local mdoc = pandoc.read(manual, "markdown")
 f:close()
-result = {}
+local result = {}
 
 function Div(elem)
   local ident = elem.identifier or ""