Troubleshoot IIS 502 errors by checking application pools, reverse proxy settings, backend services, bindings and Windows event logs.
01 Identify the 502 variant
06 Validate application health Retest the original URL and confirm successful responses under the expected load.
Review the IIS substatus and detailed error information. Different 502 codes point to different backend or proxy conditions.
Identify the 502 variant
Check application pool
Verify the application pool is running and review rapid-fail protection, identity permissions and recent restarts.
Check backend connectivity
If IIS proxies to another service, test the backend address and port directly from the IIS server.
Check bindings and certificates
Confirm host headers, ports and TLS certificates match the intended site configuration.
Review logs
Use IIS logs, Failed Request Tracing where enabled and Windows event logs to correlate the request failure.
Validate application health
Retest the original URL and confirm successful responses under the expected load.
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