The field guide

Was this site built with v0, Lovable, or Bolt?

Q: How can I tell if a site was made with Lovable?

Check three things: the domain (unedited projects stay on a lovable.app subdomain), the page source for data-lov-id attributes that Lovable stamps on elements, and script references to lovable.dev or gptengineer. Any of these is strong evidence; data-lov-id is close to conclusive.

Q: Does v0 leave a watermark?

Not a visible one, but it typically leaves a generator meta tag naming v0 and references to v0.dev in the page metadata. A developer who exports the code and cleans it up can remove these, which is why absence of fingerprints doesn't prove absence of v0.

Q: Can these fingerprints be removed?

Yes, and that's fine. Moving to a custom domain, cleaning the metadata, replacing default components and rewriting the copy removes most tells. That's not cheating a detector; that's finishing the work. Detectors like Slopdar measure the craftsmanship applied after generation, not whether AI was involved at the start.

Q: Is it bad if a site was built with v0, Lovable, or Bolt?

No. They're legitimate tools that let people ship things they couldn't build before. The fingerprints matter for context: a portfolio claiming 'hand-crafted with care' on an unedited Lovable subdomain is a different story from a weekend prototype that says what it is.

Q: What's the fastest way to check for all builders at once?

Slopdar (slopdar.com) checks fingerprints for v0, Lovable, Bolt, Base44, Replit, Framer, Webflow, Wix and a dozen smaller builders in one scan, alongside ~40 other tells, and shows the exact evidence found. Free, about ten seconds per site.

Here's the secret about AI site builders: they sign their work. Generator meta tags, stamped element attributes, scripts pointing home, default hosting subdomains. If nobody cleaned up after the tool, attribution takes one View Source and one Ctrl+F. Below are the exact fingerprints each builder leaves, straight from the checks Slopdar runs on every scan.

Before you start: open the source

Every check below happens in the page source: right-click the page, choose View Page Source, and search with Ctrl+F (Cmd+F on a Mac). You're looking in three places: meta tags near the top (especially <meta name="generator">), script URLs, and attributes on elements. The address bar counts too: builders host unedited projects on their own subdomains.

The fingerprints, builder by builder

v0 (by Vercel)

v0 generates React pages from prompts and deploys to Vercel. It announces itself in the page's metadata: a generator meta tag naming v0, or references to v0.dev among the scripts and meta tags.

How to check → View Page Source and search for 'v0'. A <meta name="generator"> tag mentioning v0, or v0.dev in script URLs, is the tell.

Lovable

Lovable (formerly GPT Engineer) is the loudest signer of the bunch. Its pages carry data-lov-id attributes on elements, projects often stay on a lovable.app subdomain, and older builds reference gptengineer scripts.

How to check → Search the source for 'data-lov-id' or 'lovable'. A site still hosted at something.lovable.app is a giveaway before you even open the source.

Bolt (by StackBlitz)

Bolt.new generates and deploys full-stack apps from a chat prompt. It leaves bolt.new references among the page's scripts and meta tags, and unedited projects tend to keep the default Vite build artifacts too.

How to check → Search the source for 'bolt.new'. Pair it with the other defaults: stock favicon, empty metadata, untouched component stack.

Base44

Base44 builds full apps from prompts and hosts them on its own domain. Unedited projects live on a base44.app subdomain and reference base44.app or base44.com in their scripts.

How to check → Check the address bar first (something.base44.app), then search the source for 'base44'.

Replit

Replit's agent deploys straight to Replit hosting: replit.app, replit.dev or the older repl.co. The hosting domain is the fingerprint; code exported elsewhere is harder to attribute.

How to check → Look at the domain. Anything ending in replit.app, replit.dev or repl.co was built and shipped on Replit.

The long tail

Create.xyz, Rocket.new, Tempo, Databutton, Softgen and friends follow the same pattern: default hosting on their own subdomain, plus script and meta references to the mothership. New builders appear monthly; the pattern never changes.

How to check → If the domain ends in the builder's name, the mystery is solved. Otherwise search the source for the builder domains listed above.

When the fingerprints are gone

A cleaned-up site isn't unattributable so much as unfingerprinted: you can no longer say which tool made it, and honestly, at that point it stops mattering. What remains detectable is the style: untouched default components, template layouts, AI copy patterns. Those are the softer tells covered in the ten signs a website is AI-generated. And if you're wondering why so many sites ship with the fingerprints still in place, that's vibe coding for you.

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Or check all of them in one scan

Slopdar runs every fingerprint check on this page, plus ~40 more tells (default stacks, AI copy patterns, leftover placeholders, template layouts), and returns a 0 to 100 Slop Score with the exact evidence found. When several builder names appear at once it discards the weak matches, because no real site was built by three competing tools; an article about Lovable shouldn't get flagged as built with it. Here's how the scoring works.

Questions people ask

How can I tell if a site was made with Lovable?+

Does v0 leave a watermark?+

Can these fingerprints be removed?+

Is it bad if a site was built with v0, Lovable, or Bolt?+

What's the fastest way to check for all builders at once?+

Run the fingerprint check →