Reference tool
Common Error Code Reference
Look up common HTTP and system error codes and fixes.
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Frequently asked questions
What is the difference between a 401 and a 403 HTTP error?
A 401 Unauthorized means the server requires authentication and the request did not include valid credentials — you need to log in. A 403 Forbidden means the server recognized your credentials but you do not have permission to access the requested resource. In practice: 401 means 'who are you?' and 403 means 'I know who you are, but you cannot be here.' If you encounter a 403, check role assignments and permissions with your administrator.
Why do I see a 502 Bad Gateway error and how do I fix it?
A 502 Bad Gateway means the server acting as a proxy or load balancer received an invalid response from an upstream server. Common causes include a crashed application server behind the load balancer, a misconfigured reverse proxy (Nginx, Cloudflare, Azure Front Door), or a deployment in progress. For end users: wait a few minutes and retry — 502s from cloud services are often transient. For operators: check the upstream application server health, review proxy timeout settings, and inspect error logs for the upstream service.
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