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HAR performance viewer

Inspect local browser network logs for slow requests, timing phases and transferred bytes.

Files can contain private browsing data. Processing is local. Report URLs omit credentials, query strings and fragments; paths may still contain sensitive information. Headers and bodies are omitted.

What it does

Inspect local browser network logs for slow requests, timing phases and transferred bytes.

How to use it

  1. Choose an exported HAR up to 10 MB / 10,000 entries.
  2. Inspect the slowest requests and waterfall offsets; export the full JSON report.
  3. Processing stays in this browser. No sign-up or upload.

Example

A request with 800 ms wait and 50 ms receive helps identify server wait versus download time.

Methodology

HAR entry timings are read without replaying requests. Transfer bytes use _transferSize, then known header plus body sizes.

Limitations

Unknown sizes remain unknown. SSL overlaps connection time; durations must not be summed into page-load time. URLs omit queries, fragments and credentials but paths may be sensitive.

Automation

This tool runs in your browser. No upload API or MCP endpoint is available.

View capabilities and documentation

Reference updated

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