HTTP 422 Unprocessable Content vs 502 Bad Gateway
HTTP 422 (Unprocessable Content) is a 4xx Client Error response, while 502 (Bad Gateway) is a 5xx Server Error response. 422 indicates that the server understands the content type and syntax, but was unable to process the contained instructions. Common in API validation errors. In contrast, 502 means that the server, acting as a gateway or proxy, received an invalid response from the upstream server.
Description
The server understands the content type and syntax, but was unable to process the contained instructions. Common in API validation errors.
When You See It
When form validation fails — correct syntax but invalid data (e.g., email format wrong, date in the past).
How to Fix
Check the response body for specific validation errors and correct the input data.
Description
The server, acting as a gateway or proxy, received an invalid response from the upstream server.
When You See It
When Nginx/Apache can't reach the application server (e.g., Gunicorn is down, upstream timeout).
How to Fix
Check if the upstream server is running. Verify proxy configuration. Check for upstream timeouts.
Key Differences
422 is a 4xx Client Error response, while 502 is a 5xx Server Error response.
HTTP 422: The server understands the content type and syntax, but was unable to process the contained instructions. Common in API validation errors.
HTTP 502: The server, acting as a gateway or proxy, received an invalid response from the upstream server.
You encounter 422 when when form validation fails — correct syntax but invalid data (e.g., email format wrong, date in the past).
You encounter 502 when when Nginx/Apache can't reach the application server (e.g., Gunicorn is down, upstream timeout).
When to Use Which
For 422 (Unprocessable Content): Check the response body for specific validation errors and correct the input data. For 502 (Bad Gateway): Check if the upstream server is running. Verify proxy configuration. Check for upstream timeouts.