Two ways, depending on where the site lives
Onlay hosts it. Your agent built a static site or a single-page app. Push the build folder:
onlay push dist/
Every file goes up as it is, under one link. Every HTML page takes comments, and each thread is filed under its page. A pull names the page and quotes the source lines from that page's file. Up to 2,000 files and 200 MB. Pushing a folder is part of Pro and needs the CLI.
You host it. The app runs on your own deploy (Vercel, Netlify, your own servers). Add Onlay with one script tag in the layout:
onlay app add myapp.com --host https://myapp.com
That prints the tag. It does nothing for a visitor without a review link, so public pages are unaffected. Make a review link with onlay app link myapp.com and send it. Reviewers comment on the real pages at their real URLs, with pictures and drawings. Production and each branch's preview are separate environments. Apps are part of Pro.
What your agent gets
onlay pull myapp.com
Each thread names the page it was left on and the words or element it points at, and says when the reader was on a narrow screen, in dark mode, or inside a dialog or a tab. With the optional build plugin for Vite, Next, webpack and others, each thread also says which file and line drew the element: drawn at src/components/hero.tsx:12. Onlay does not search your code or guess; your agent has the checkout and finds the words there.
Differences from a single document
On an app, readers comment but do not edit text in place. Comments on any page of a pushed folder come back on the same pull. The docs cover every command.
When something else fits better
If your site already deploys to Vercel and your reviewers are on your Vercel team, Vercel's preview comments are built in, and Vercel's MCP server can read them. For bug reports from users of a site in production, with console logs and browser details, a bug-capture tool is the better fit. See the comparisons.