diff --git a/package-lock.json b/package-lock.json
index cdcaec9e..22d02159 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -8,6 +8,7 @@
       "name": "phanpy",
       "version": "0.1.0",
       "dependencies": {
+        "@formatjs/intl-localematcher": "~0.2.32",
         "@github/text-expander-element": "~2.3.0",
         "@iconify-icons/mingcute": "~1.2.4",
         "@szhsin/react-menu": "~3.5.1",
@@ -2508,6 +2509,14 @@
         "node": ">=12"
       }
     },
+    "node_modules/@formatjs/intl-localematcher": {
+      "version": "0.2.32",
+      "resolved": "https://registry.npmjs.org/@formatjs/intl-localematcher/-/intl-localematcher-0.2.32.tgz",
+      "integrity": "sha512-k/MEBstff4sttohyEpXxCmC3MqbUn9VvHGlZ8fauLzkbwXmVrEeyzS+4uhrvAk9DWU9/7otYWxyDox4nT/KVLQ==",
+      "dependencies": {
+        "tslib": "^2.4.0"
+      }
+    },
     "node_modules/@github/combobox-nav": {
       "version": "2.1.5",
       "resolved": "https://registry.npmjs.org/@github/combobox-nav/-/combobox-nav-2.1.5.tgz",
@@ -8694,6 +8703,14 @@
       "dev": true,
       "optional": true
     },
+    "@formatjs/intl-localematcher": {
+      "version": "0.2.32",
+      "resolved": "https://registry.npmjs.org/@formatjs/intl-localematcher/-/intl-localematcher-0.2.32.tgz",
+      "integrity": "sha512-k/MEBstff4sttohyEpXxCmC3MqbUn9VvHGlZ8fauLzkbwXmVrEeyzS+4uhrvAk9DWU9/7otYWxyDox4nT/KVLQ==",
+      "requires": {
+        "tslib": "^2.4.0"
+      }
+    },
     "@github/combobox-nav": {
       "version": "2.1.5",
       "resolved": "https://registry.npmjs.org/@github/combobox-nav/-/combobox-nav-2.1.5.tgz",
diff --git a/package.json b/package.json
index bc5bff5d..2ee389b7 100644
--- a/package.json
+++ b/package.json
@@ -10,6 +10,7 @@
     "sourcemap": "npx source-map-explorer dist/assets/*.js"
   },
   "dependencies": {
+    "@formatjs/intl-localematcher": "~0.2.32",
     "@github/text-expander-element": "~2.3.0",
     "@iconify-icons/mingcute": "~1.2.4",
     "@szhsin/react-menu": "~3.5.1",
diff --git a/src/components/compose.jsx b/src/components/compose.jsx
index ca0ca335..0eafecf0 100644
--- a/src/components/compose.jsx
+++ b/src/components/compose.jsx
@@ -1,5 +1,6 @@
 import './compose.css';
 
+import { match } from '@formatjs/intl-localematcher';
 import '@github/text-expander-element';
 import equal from 'fast-deep-equal';
 import { forwardRef } from 'preact/compat';
@@ -84,7 +85,11 @@ const observer = new IntersectionObserver((entries) => {
 });
 observer.observe(menu);
 
-const DEFAULT_LANG = 'en';
+const DEFAULT_LANG = match(
+  [new Intl.DateTimeFormat().resolvedOptions().locale, ...navigator.languages],
+  supportedLanguages.map((l) => l[0]),
+  'en',
+);
 
 // https://github.com/mastodon/mastodon/blob/c4a429ed47e85a6bbf0d470a41cc2f64cf120c19/app/javascript/mastodon/features/compose/util/counter.js
 const urlRegexObj = new RegExp(urlRegex.source, urlRegex.flags);