diff --git a/src/apps/settings/index.tsx b/src/apps/settings/index.tsx
index 1b5b643..d2c431b 100644
--- a/src/apps/settings/index.tsx
+++ b/src/apps/settings/index.tsx
@@ -24,6 +24,7 @@ import {
   CURATED_WALLPAPERS,
   DEFAULT_CURATED_ID,
   isSafeWallpaperUrl,
+  MAX_WALLPAPER_URL_LENGTH,
   resolveCurated,
   type WallpaperFit,
 } from '@/lib/wallpaper';
@@ -207,6 +208,10 @@ export function WallpaperSection() {
       toast({ title: 'Enter a valid https:// image URL', variant: 'destructive' });
       return;
     }
+    if (trimmed.length > MAX_WALLPAPER_URL_LENGTH) {
+      toast({ title: 'That URL is too long', description: `URLs must be ${MAX_WALLPAPER_URL_LENGTH} characters or fewer.`, variant: 'destructive' });
+      return;
+    }
     setPendingPreviewUrl(trimmed);
   };
 
diff --git a/src/lib/wallpaper.ts b/src/lib/wallpaper.ts
index 33b541f..3f286ec 100644
--- a/src/lib/wallpaper.ts
+++ b/src/lib/wallpaper.ts
@@ -90,6 +90,9 @@ export function sanitizeWallpaperUrl(value: string | undefined): string | undefi
   return isSafeWallpaperUrl(value) ? value : undefined;
 }
 
+/** Kept in sync with the Zod schema's `url` length cap below. */
+export const MAX_WALLPAPER_URL_LENGTH = 2048;
+
 const WallpaperPresentationSchema = z.object({
   fit: z.enum(['cover', 'contain']),
   dim: z.number().min(0).max(80),
@@ -102,7 +105,7 @@ const CuratedSelectionSchema = z.object({
 
 const UrlSelectionSchema = z.object({
   source: z.literal('url'),
-  url: z.string().max(2048).refine(isSafeWallpaperUrl, 'Wallpaper URL must be a valid https:// URL'),
+  url: z.string().max(MAX_WALLPAPER_URL_LENGTH).refine(isSafeWallpaperUrl, 'Wallpaper URL must be a valid https:// URL'),
   presentation: WallpaperPresentationSchema,
 });