diff --git a/src/app.jsx b/src/app.jsx
index c8cccc91..86cf33e5 100644
--- a/src/app.jsx
+++ b/src/app.jsx
@@ -82,7 +82,7 @@ function App() {
         let account = accounts.find((a) => a.info.id === mastoAccount.id);
         if (account) {
           account.info = mastoAccount;
-          account.instanceURL = instanceURL;
+          account.instanceURL = instanceURL.toLowerCase();
           account.accessToken = accessToken;
         } else {
           account = {
@@ -166,7 +166,7 @@ function App() {
           console.log(info);
           const { uri, domain } = info;
           const instances = store.local.getJSON('instances') || {};
-          instances[domain || uri] = info;
+          instances[(domain || uri).toLowerCase()] = info;
           store.local.setJSON('instances', instances);
         })();
       });
diff --git a/src/components/compose.jsx b/src/components/compose.jsx
index 05fda4bd..ac059ce5 100644
--- a/src/components/compose.jsx
+++ b/src/components/compose.jsx
@@ -73,9 +73,9 @@ function Compose({
   const configuration = useMemo(() => {
     try {
       const instances = store.local.getJSON('instances');
-      const currentInstance = accounts.find(
-        (a) => a.info.id === currentAccount,
-      ).instanceURL;
+      const currentInstance = accounts
+        .find((a) => a.info.id === currentAccount)
+        .instanceURL.toLowerCase();
       const config = instances[currentInstance].configuration;
       console.log(config);
       return config;
diff --git a/src/pages/login.jsx b/src/pages/login.jsx
index fcf797ce..63312d5c 100644
--- a/src/pages/login.jsx
+++ b/src/pages/login.jsx
@@ -16,14 +16,14 @@ function Login() {
 
   useEffect(() => {
     if (cachedInstanceURL) {
-      instanceURLRef.current.value = cachedInstanceURL;
+      instanceURLRef.current.value = cachedInstanceURL.toLowerCase();
     }
   }, []);
 
   const onSubmit = (e) => {
     e.preventDefault();
     const { elements } = e.target;
-    let instanceURL = elements.instanceURL.value;
+    let instanceURL = elements.instanceURL.value.toLowerCase();
     // Remove protocol from instance URL
     instanceURL = instanceURL.replace(/(^\w+:|^)\/\//, '');
     store.local.set('instanceURL', instanceURL);