Show HN: Testmagic.link – Zero-setup magic link testing for coding agents

I know there are existing email testing services, but the ones I found require signing up, getting credentials, and integrating an API. That felt like overkill when I just wanted to tell Claude Code: "test the email sign-in using testmagic.link".

So I made testmagic.link. No signup, no API keys, no integration. It’s basically a one-liner with a domain that’s easy to remember. I also added an llms.txt file at the root, so agents instantly know how to read the inbox without me explaining it.

There’s also an optional mail-scanner simulation: add ?prefetch=1 to the inbox URL, and testmagic.link will GET each message’s magic link once before you open it, without following redirects — similar to how Outlook Safe Links or a corporate mail scanner might prefetch links. This is useful for catching magic-link flows that break when a security scanner visits a single-use link first.

Would love to hear your feedback, or if you've run into any other weird email auth edge cases I should simulate. I'll be around to answer questions!