250 handcrafted themes with living, animated backgrounds — from quiet dark modes to cherry blossoms and aurora, to a black hole, neon city streets, and a whole arcade of playable-looking classics. Set the speed of any of them. One click, both platforms.
Three quick steps — and one that really matters.
Install Vellum free from the Chrome Web Store. It works on both Claude and ChatGPT — no account or setup needed.
In Claude or ChatGPT settings, set appearance to Dark. Vellum's themes are crafted for dark mode — on light mode they'll look washed out.
Click the Vellum icon in your toolbar, choose any theme, and it applies instantly across the whole interface.
Why dark mode? Vellum's animated backgrounds and palettes are designed to glow against a dark interface. If a theme looks faded, you're still in light mode — switch your AI app to Dark in its appearance settings and it'll come alive.
10 free · 240 Pro
Pick a theme and it applies at once — sidebar, composer, buttons, scrollbars. The entire interface, retuned.
Cherry blossoms, northern lights, rising embers, a retro synthwave grid. Subtle enough to work against, striking enough to enjoy.
Every animated theme has a speed dial, from 10% to full. Turn a busy one down until it barely drifts. The slowdown happens inside the animation, so it stays smooth rather than juddering.
Drop in any picture and Vellum reads a palette out of it, so the sidebar, composer and text settle around your image instead of fighting it. It stays on your machine.
250 is a lot to scroll. Filter by category, search by name or by what you actually mean — “japan”, “oled”, “rain” — and star the ones you keep returning to.
No tracking, analytics, or telemetry. No account. Beyond checking a Pro key, the extension talks to nobody — it ships every font and pixel it uses. Your theme choice syncs through Chrome; that is the whole of it.
Every install starts with a 7-day Pro trial. Keep 10 themes free forever, or unlock all 250.
250 themes. Two platforms. One click. Free to start.
Add to Chrome — Free