Common error codes

Updated July 2026 · 2 min read

Your tagging endpoint answers every request with a standard HTTP status code. Reading that code is the fastest way to tell whether the problem is in the browser, the container or the URL between them.

Where to find the codes

• Browser DevTools — the Network tab shows the status of every request your site sends to your tagging domain.
• Container logs — show the same requests as the server saw them, with the response code for each.

2xx — the request was accepted

200 or 204 means the container received and accepted the request. If events still don't reach the platform, the problem is inside the server container's tags — open Preview and debug mode and check which tags fire and what the platform answers.

4xx — the request was rejected

The endpoint is reachable but refused what it got. Typical meanings:

• 400 — no client in your server container claimed the request. The matching client (the GA4 client, for example) is missing, disabled or listening on a different request path.
• 404 — the URL is wrong: a typo or stray path in the server container URL your web tags send to.
• 401 / 403 — something in front of the endpoint is blocking the request, such as a firewall or security rule at your DNS provider.

5xx — the container couldn't respond

• 500 — an error inside the container, often a broken custom template or a misconfigured tag.
• 502 / 503 — the container is temporarily unreachable: still provisioning, restarting or briefly overloaded. These usually clear on their own.

If a 5xx persists, check the container's status in the app, then run the Events not showing up checklist.