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The TryFast inspector#
The TryFast inspector is the program that fetches a web page when someone asks TryFast to check it. If you found it in your server logs, this page explains what it does and why.
How it identifies itself#
User-Agent: TryFastInspector/1 (+https://tryfast.eu/docs/inspect)
When it fetches a page#
Only on request, one URL at a time. It never crawls or follows links on its own:
- Install checks: a TryFast customer (or their AI agent) asks whether the TryFast snippet is installed correctly on a page of their own website ("Check a page" in the app,
verify_installation,POST /api/v1/projects/{id}/install-check). - Page inspection: a customer's AI agent asks for the structure of a page of the customer's website to find stable selectors for an experiment (
inspect_page). - AI agent registration: when an AI client connects to TryFast's MCP server, TryFast fetches the client's public metadata document from the client's own website (for example claude.ai) to show its name in the consent window.
A customer can only check URLs on the domains of their own TryFast project.
What it does and does not do#
- It sends one
GETrequest (following at most 5 redirects, each of which must stay on the project's domains), with no cookies and no login. - It reads at most 2 MB of HTML and gives up after 10 seconds. Client metadata documents are limited to 16 KB and 5 seconds.
- It does not run JavaScript, submit forms, load images or follow links.
- It only connects to public addresses on ports 443 and 80; private, local and reserved network addresses are refused.
- It is rate limited per TryFast workspace (30 requests a minute) and runs at most 8 requests at a time in total.
- It returns to the customer only structural information: the title, language, headings, buttons, links, forms (field names and types, never values), image alt texts, whether the snippet is present, and suggested selectors. Texts are cut to 200 characters.
Allow or block it#
If your bot protection blocks the inspector, the customer's check reports fetch_blocked; TryFast still sees real visits through the snippet, so blocking it never breaks anything. To allow it, allowlist the user agent above. To have it stop checking your site, write to support@tryfast.eu with the domain.
Contact#
Questions or concerns: support@tryfast.eu. Security reports: security@tryfast.eu (vulnerability disclosure policy).