Guide
Case: sign-up emails still linked to localhost although the settings looked right
Updated
This is our own test app, not a customer's. New users got a confirmation email whose link opened localhost:3000, a dead end for anyone but the app's owner. The Site URL setting already showed the live address, and the app's own code asked for the live page, which was on the allowed list.
Why it happens
A settings screen and a code review can both say "fixed" while real emails still behave the old way. Only a real sign-up, reading the real email, showed the difference.
Possible causes
- What happened here: the builder's AI said the sign-in service was still running with its old settings. After a backend restart, the next real sign-up landed on the live site. We saw this once, on this one app, so treat it as a possibility, not a rule.
- The Site URL setting is still the default local address.
- The live address is missing from the allowed redirect list.
- The preview or local address is written into the app's own code.
You can't see it yourself
You're signed in, your customers aren't. You are already signed in, so you never receive that email. The bug was first spotted on 16 October 2026 and the check that showed the change was run on 17 October 2026.
Related: The confirmation link in my sign-up email opens localhost · Sign-up or login broken after publishing: users bounce back to login or land on localhost · My builder says the app is tested, but my customers hit problems
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