HTTP
503 Service Unavailable
The server is temporarily unable to handle the request due to maintenance or overload. Should include a Retry-After header.
When You See This Code
During maintenance windows, server overload, or when the application pool is exhausted.
How to Fix
Wait and retry. Check the Retry-After header. Scale up servers if it's a capacity issue.
Specification
View RFC / Specification →Related Codes
Cross-Protocol Equivalents
Comparisons
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