Why aren’t rules applying?

Scope or timing issues can prevent rules from firing. Prefer MV3 DNR with explicit URL patterns.

Is there a more predictable option?

VibeHeader 1.1 keeps headers in named Profiles, scopes them with Request Filters, and includes a URL tester so you can verify a target request before reloading the page.

ModHeader Rules Not Applying? Try a Lightweight Alternative

See which Profile is active, limit it to the intended request URLs, and test the scope before you return to your app.

TL;DR: A header can miss because the target request URL differs from the address bar, a filter is disabled, or another active Profile overrides the same name. VibeHeader makes each of those states visible.

Explore the alternative Install for Chrome Manual install

VibeHeader 1.1 editing two request headers with a Request Filter active on the current tab

Troubleshooting basics

Test the exact document, fetch, XHR, or asset URL—not only the page URL in the address bar.
Confirm the Request Filter and Profile are both enabled.
If multiple Profiles set the same header, the later Profile takes priority; check the override warning.
Reload, then inspect the effective request in DevTools → Network.