How to tell if a website was built with Replit

To tell if a website was built with Replit, check the address and the response headers. Replit is an online coding platform: people write, run and publish code there, and since its Replit Agent launched, many also have AI build entire apps from a prompt. Both kinds of project end up on the same hosting. That makes Replit easy to spot but harder to read than builders like Lovable or Bolt.

Replit's hosting domains

• *.replit.app: apps published with Replit Deployments
• *.replit.dev: development previews of a project while someone works on it
• *.repl.co: an older Replit domain still seen on some projects

An address on any of these tells you the site runs on Replit. It does not, by itself, tell you whether a person or Replit Agent wrote it.

The replit-cluster header

Replit hosting adds a replit-cluster header to its responses. On a custom domain, this is how you find out a site is still served by Replit. Open the developer tools (F12, or Option+Command+I on a Mac), go to Network, reload, click the first request and look under Response Headers. Some Replit-hosted sites also show a reference to .repl.it in an expect-ct header.

Banners and badges

Search the page source (Ctrl+U) for replit. You may find:

• replit-dev-banner: a script that shows a small banner on development previews
• replit-badge: a "made with Replit" badge some projects display

These confirm Replit, with the same caveat: they say where the project lives, not who wrote it.

Why Replit counts for less

Lovable, Bolt, v0 and Base44 exist to generate apps with AI, so their fingerprints strongly suggest an AI-built site. Replit is different. Students, hobbyists and professional developers have written code by hand on Replit for years, and many still do. A replit.app address is roughly as informative as a vercel.app or netlify.app one: it names the host.

That is why Kitsuvo gives Replit hosting about half the weight of the dedicated AI builders' domains, and looks for other signs before calling a Replit site AI-built.

Signs a Replit site came from Replit Agent

To tell an Agent-built app from hand-written code, look for the same supporting signs as any vibe-coded site:

• The common AI stack: React with Tailwind CSS and shadcn/ui class names such as text-muted-foreground.
• Template leftovers: a default tab title, a stock favicon, placeholder people like John Doe in testimonials.
• Stock copy: dense use of the phrases in our AI copy guide.
• The stock landing-page sequence: badge, headline, three feature cards, testimonials, pricing.

Several of these together on a Replit site make "possibly vibe coded" a fair reading. A hand-written Python dashboard with plain HTML on replit.app would not match, and shouldn't be called AI-built.

Worked example

Two made-up sites, both on Replit:

• habit-garden.replit.app uses React, shadcn/ui cards, a violet gradient hero, the title Habit Garden - Grow Better Habits and copy that promises to transform your daily routine. Replit hosting plus the stack plus stock copy: Possibly vibe coded, builder Replit.
• physics-lab-notes.replit.app is a single page of plain HTML with a hand-drawn diagram, a student's name and a Python backend. Replit hosting and nothing else: No strong AI signs.

Same host, different stories. The host is a starting point, not a verdict.

Checking automatically

Kitsuvo, our no-AI web browser, reads the hosting, headers and source of every page you open and weighs Replit's traces at their real strength. It names Replit when it finds them and shows every signal it counted. For the dedicated AI builders, see the guides to Lovable, Bolt, v0 and Base44.