diff --git a/.cspell/dart_flutter.txt b/.cspell/dart_flutter.txt
new file mode 100644
index 00000000..0639e559
--- /dev/null
+++ b/.cspell/dart_flutter.txt
@@ -0,0 +1,9 @@
+autofocus
+gapless
+lerp
+pubspec
+sublist
+todos
+unawaited
+unfocus
+writeln
diff --git a/.cspell/misc.txt b/.cspell/misc.txt
new file mode 100644
index 00000000..94f59994
--- /dev/null
+++ b/.cspell/misc.txt
@@ -0,0 +1,11 @@
+browsable
+cleartext
+deeplinking
+flathub
+foss
+fullscreen
+playstore
+postmarket
+provokateurin
+subroutes
+uncategorized
diff --git a/.cspell/neon.txt b/.cspell/neon.txt
new file mode 100644
index 00000000..175b008f
--- /dev/null
+++ b/.cspell/neon.txt
@@ -0,0 +1,20 @@
+crypton
+exportables
+fcmup
+filesize
+gotify
+heckel
+mocktail
+nextpush
+noprovider
+ntfy
+oled
+oledas
+rxdart
+seti
+siacs
+sqflite
+underspecified
+updateshouldnotify
+wakelock
+zxing
diff --git a/.cspell/nextcloud.txt b/.cspell/nextcloud.txt
new file mode 100644
index 00000000..0880b4e9
--- /dev/null
+++ b/.cspell/nextcloud.txt
@@ -0,0 +1,71 @@
+apirequest
+applist
+apppassword
+approximative
+appstore
+bigfilechunking
+bools
+bulkupload
+commenters
+csapi
+datetime
+deletedshares
+displayname
+etag
+fediverse
+getapppassword
+groupid
+hovercard
+iscustomavatar
+itemsperpage
+keepalive
+keypair
+lastmod
+licence
+logfile
+logoheader
+mimetypes
+mountpoint
+navigations
+nextcloud
+nextcloud's
+openlocaleditor
+organisation
+prio
+productname
+publicpreview
+reshares
+resharing
+rgdnvw
+r'sharebymail
+r'updatenotification
+r'uppush
+shareapi
+sharebymail
+sharee
+shareesapi
+shareinfo
+statuscode
+stime
+stylesheet
+subadmin
+subadmins
+subfiles
+subline
+tasktypes
+textprocessing
+totalitems
+transferownership
+trashbin
+undelete
+unifiedpush
+unsharing
+unstar
+updatenotification
+uppush
+usercount
+usergroup
+userid
+userroom
+versionstring
+whatsnew
diff --git a/.cspell/tools.txt b/.cspell/tools.txt
new file mode 100644
index 00000000..35a57397
--- /dev/null
+++ b/.cspell/tools.txt
@@ -0,0 +1,60 @@
+aarch
+allprojects
+appindicator
+autoptr
+buildscript
+buildsystem
+buildx
+cest
+classpath
+cloc
+commitlint
+dapplication
+dists
+endforeach
+endfunction
+endlegend
+endswith
+enduml
+euxo
+exiftool
+extglob
+freedesktop
+fullpath
+gboolean
+gchar
+genhtml
+gradlew
+hicolor
+icudtl
+inkscape
+intellij
+jetbrains
+jvmargs
+klass
+lcov
+libapp
+libappindicator
+libayatana
+libflutter
+libindicator
+libsqlite
+mipmap
+ndebug
+nproc
+plantuml
+precache
+puml
+rpath
+startuml
+stdlib
+strconcat
+strdupv
+strfreev
+subprojects
+sysroot
+tsvg
+werror
+workdir
+xxxh
+xxxhdpi
diff --git a/.cspell/webdav.txt b/.cspell/webdav.txt
new file mode 100644
index 00000000..8085aee1
--- /dev/null
+++ b/.cspell/webdav.txt
@@ -0,0 +1,50 @@
+copymove
+dasl
+davgetcontentlength
+davgetcontenttype
+davgetetag
+davgetlastmodified
+davresourcetype
+fileid
+getcontentlength
+getcontenttype
+getetag
+getlastmodified
+largefile
+mkcol
+multistatus
+nccreationtime
+ncdatafingerprint
+nchaspreview
+ncisencrypted
+ncmetadataetag
+ncmounttype
+ncnote
+ncrichworkspace
+ncuploadtime
+nodestcoll
+noncoll
+noparent
+occommentscount
+occommentshref
+occommentsunread
+ocdownloadurl
+ocfavorite
+ocfileid
+ocid
+ocmsharepermissions
+ocownerdisplayname
+ocownerid
+ocpermissions
+ocsize
+ocssharepermissions
+owncloud
+propertyupdate
+propfind
+proppatch
+propstat
+propstats
+resourcetype
+sharees
+systemtag
+webdav
diff --git a/.github/workflows/spellcheck.yaml b/.github/workflows/spellcheck.yaml
new file mode 100644
index 00000000..65e0751b
--- /dev/null
+++ b/.github/workflows/spellcheck.yaml
@@ -0,0 +1,10 @@
+name: 'Check spelling'
+on:
+  pull_request:
+
+jobs:
+  spellcheck:
+    runs-on: ubuntu-22.04
+    steps:
+      - uses: actions/checkout@v4
+      - uses: streetsidesoftware/cspell-action@v3
diff --git a/cspell.json b/cspell.json
new file mode 100644
index 00000000..eb3a04ff
--- /dev/null
+++ b/cspell.json
@@ -0,0 +1,60 @@
+{
+  "version": "0.2",
+  "language": "en",
+  "words": [
+    "OpenAPI"
+  ],
+  "ignorePaths": [
+    "**.iml",
+    "**.log",
+    "**.svg",
+    "**/assets/**",
+    "**/build/**",
+    "**/coverage/**",
+    "**/ephemeral/**",
+    "**/l10n/!(en.arb)",
+    "external",
+    "packages/app/android/app/src/main/java/io/flutter/plugins/GeneratedPluginRegistrant.java",
+    "packages/app/android/gradlew*",
+    "packages/file_icons/lib/src/data.dart",
+    "packages/neon_lints/lib",
+    "packages/nextcloud/test/files"
+  ],
+  "dictionaries": [
+    "bash",
+    "dart_flutter",
+    "en_US",
+    "misc",
+    "neon",
+    "nextcloud",
+    "softwareTerms",
+    "tools",
+    "webdav"
+  ],
+  "dictionaryDefinitions": [
+    {
+      "name": "dart_flutter",
+      "path": ".cspell/dart_flutter.txt"
+    },
+    {
+      "name": "misc",
+      "path": ".cspell/misc.txt"
+    },
+    {
+      "name": "neon",
+      "path": ".cspell/neon.txt"
+    },
+    {
+      "name": "nextcloud",
+      "path": ".cspell/nextcloud.txt"
+    },
+    {
+      "name": "tools",
+      "path": ".cspell/tools.txt"
+    },
+    {
+      "name": "webdav",
+      "path": ".cspell/webdav.txt"
+    }
+  ]
+}
diff --git a/tool/update-cspell-dictionaries.sh b/tool/update-cspell-dictionaries.sh
new file mode 100755
index 00000000..18dd4e78
--- /dev/null
+++ b/tool/update-cspell-dictionaries.sh
@@ -0,0 +1,8 @@
+#!/bin/bash
+set -euxo pipefail
+cd "$(dirname "$0")/.."
+
+for file in .cspell/*; do
+  rm "$file"
+  cspell lint --quiet --unique --words-only . | tr '[:upper:]' '[:lower:]' | sort -f | uniq > "$file" || true
+done