Bolt.new is StackBlitz’s AI builder: you describe an app, it writes a full project in the browser, and you can publish it in one click. Its sites are harder to recognise than Lovable’s, because Bolt’s starter writes little of its own into the page. In our accuracy test we name Bolt on 15 of 23 Bolt sites (65%); the others keep nothing we can tie to it.
Here are the traces we look for, from the strongest.
1. A .bolt.host address
Sites published on Bolt’s own hosting, Bolt Cloud, live at an address ending in .bolt.host. That is as clear as it gets: Bolt is serving the site.
2. A custom domain pointed at Bolt
Bolt’s domain guide asks owners who connect their own domain to add a CNAME record pointing to site-dns.bolt.host. Any DNS lookup tool shows it; we read a site’s DNS records with every scan.
3. The “Built with Bolt” badge
Bolt offers a badge that sites can show. Its images keep the names Bolt ships them with, such as white_circle_360x360.png, black_circle_360x360.png or logotext_poweredby_360w.png, and often load from Bolt’s own storage. Right-click the badge and open the image in a new tab to see its address. We look for these names in the page and in the site’s own scripts.
4. A header naming Bolt
Some pages Bolt serves answer with an x-powered-by header that names Bolt. Your browser’s developer tools show it in the Network tab, under the page’s response headers.
Weaker traces, counted only together
Most Bolt projects are published to Netlify, and Bolt’s starter is a Vite app that keeps Vite’s own icon (vite.svg), uses the Lucide icon set and often stores its data in a Supabase project. Each of these is common on sites built by hand: Netlify, a Vite build and Vite’s icon together fit one in five hand-made Vite projects on Netlify. With Lucide and a Supabase project as well, they fit 1.4% of them. So we count the five only together, and rate them Medium, never High.
What doesn’t count
A link to bolt.new is not a trace. Design blogs, tutorials and documentation link to it all the time, so a link never counts, only what Bolt itself puts in the page.
How sure can you be?
Traces 1 to 4 are Bolt’s own, and any one of them is a builder signature: we rate the AI traces High. The starter combination is weaker, and says so.
The reverse doesn’t hold. A Bolt project downloaded and hosted elsewhere, with its badge removed and its icon changed, looks like any other Vite app, and “none found” is never proof that a site wasn’t made with Bolt or any AI tool.
And being made with Bolt says nothing about whether a business is honest. It’s a fact about how a site was built, not a judgement of the people behind it.
Check any site for these traces at once: the AI Website Detector shows each one it finds, with the exact line from the page.