HTTP Error Logs
Windows HTTP Error Logs are kernel-mode HTTP.sys log files written under %WinDir%\System32\LogFiles\HTTPERR when the HTTP Server API rejects or drops requests before they reach IIS or another application. They record low-level connection failures such as URL parsing errors, malformed requests, timer expirations, connection resets, queue overflows, and SSL handshake problems so administrators can diagnose why clients saw resets, 400-series errors, or failed connections. Kudu removes old rotated HTTPERR text log files to reclaim disk space without touching websites, bindings, certificates, application data, settings, accounts, or passwords.
Why clean HTTP Error Logs?
- Months of accumulated HTTPERR rollover files can consume significant space on the system drive, and users usually notice low disk space warnings or failed updates before they realize kernel HTTP logs are growing.
- Repeated bot traffic, malformed requests, or TLS negotiation failures can flood HTTPERR with entries, making the folder grow rapidly while the visible symptom is a busy web server and unexpectedly large Windows log directories.
- Very large numbers of old log files slow manual troubleshooting because opening, searching, and copying the folder becomes cumbersome when an administrator is trying to investigate current 400, connection reset, or timeout events.
- Retaining stale HTTPERR logs after an incident mixes obsolete connection failures with current ones, so administrators may chase old Timer_ConnectionIdle, Connection_Dropped, or SSL errors that no longer match what clients are seeing now.
- These logs are append-only diagnostics rather than an active runtime cache, so cleaning them does not reset IIS sites or delete content, but it does remove historical evidence that would otherwise clutter incident reviews.
- On busy servers, oversized HTTPERR history can lengthen backup, antivirus, and file indexing work on the Windows directory, which users may notice as slower maintenance windows or longer scans even though the web apps themselves are unchanged.
Cache paths Kudu targets
Windows
%WinDir%/System32/LogFiles/HTTPERR |
Common questions about HTTP Error Logs
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