The Traefik regex that silently keeps your old config

You edit a redirect, apply it, and nothing changes — no error, no warning. The culprit is a quoting rule you’ll only learn the hard way.

The one-character bug

In Traefik dynamic YAML, a redirectRegex written with double quotes lets YAML eat the backslash in \. before Traefik sees it. The regex becomes invalid, Traefik silently rejects the whole dynamic config, and keeps serving the last good version. Your change never took — and nothing told you.

Wrong (silently ignored)

regex: "^https://old\.example\.com/(.*)"

Right (single quotes)

regex: '^https://old\.example\.com/(.*)'

Single-quote your regexes in YAML. Double quotes turn \. into a trap that fails quietly.

The general lesson: when a config change “doesn’t take” with no error, assume the whole document was rejected and the old one is still live. Check the loader’s logs, not just the endpoint.