diff --git a/src/routes/(app)/[username]/components/ChangeHandleModal.svelte b/src/routes/(app)/[username]/components/ChangeHandleModal.svelte
index 84285a81..f097fb04 100644
--- a/src/routes/(app)/[username]/components/ChangeHandleModal.svelte
+++ b/src/routes/(app)/[username]/components/ChangeHandleModal.svelte
@@ -24,6 +24,10 @@
 
 	let selectedTab = $state(0);
 	let handle = $state('');
+	$effect(() => {
+		const lowercase = handle.toLowerCase();
+		if (lowercase != handle) handle = lowercase;
+	});
 	let domain = $state('');
 	let error = $state(null) as null | string;
 	let publicSuffix = $state(usernames.defaultSuffix());
diff --git a/src/routes/(app)/claim-handle/components/ClaimHandleForm.svelte b/src/routes/(app)/claim-handle/components/ClaimHandleForm.svelte
index 082c3990..14288b00 100644
--- a/src/routes/(app)/claim-handle/components/ClaimHandleForm.svelte
+++ b/src/routes/(app)/claim-handle/components/ClaimHandleForm.svelte
@@ -14,6 +14,10 @@
 	} = $props();
 
 	let handle = $state('');
+	$effect(() => {
+		const lowercase = handle.toLowerCase();
+		if (lowercase != handle) handle = lowercase;
+	});
 	let randomNumberSuffix = $state(usernames.genRandomUsernameSuffix());
 	let publicSuffix = $state(usernames.defaultSuffix());
 	let fullHandleSuffix = $derived(