AI API error 503: unavailable or overloaded endpoints
A 503 means the responding endpoint is unavailable for this request. Read its error details and the matching official report; it does not by itself confirm a global outage.
Quick answer
A 503 means the responding endpoint is unavailable for this request. Read its error details and the matching official report; it does not by itself confirm a global outage.
Provider differences
OpenAI documents 503 overload responses, including server_is_overloaded. Honor Retry-After when supplied. Gemini identifies 503 UNAVAILABLE as a transient error for which bounded backoff can be appropriate.
Claude’s direct API documents 529 for overload. A 503 seen through a gateway should be attributed to the responding layer until you have further evidence.
Recommended application response
Use exponential backoff with jitter and an explicit attempt and time budget. Avoid sending the same failed request in a tight loop. Keep a request ID and sanitized response details for investigation.
If you consider another endpoint, verify its supported model, authentication, data handling and actual response. A normal status page is only one piece of evidence. A router’s report cannot establish every upstream model’s availability.
Related service pages
Each entry shows its own collection coverage. A linked service is not necessarily automatically collected.
Editorial review date applies to this guide. Live report collection times appear on the service pages.