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WireTrail user guide

Command-line HAR analysis

Follow the request. Find the cause.

WireTrail reads HAR network captures from the command line. It groups repeated calls, finds the failures and the slow requests, ranks the likely causes, and compares one capture with another. Output is plain text, with JSON for scripts and CI. Most commands take about half a second on a 150 MB capture.

Start your first triage Install WireTrail

HAR / Investigation
# Start with one question
$ wiretrail checkout.har diagnose --top 3

[HIGH] retry-exhaustion — 4 retries, final 500 on POST /v1/cart/sync
  repeated retries did not recover
  evidence: e000069, e000070, e000072, e000073, e000076
  -> wiretrail <file> retries
...
[HIGH] rate-limit-no-backoff — calls during 429 cooldown on search.shop.example /v1/suggest
  4 429s, follow-ups before Retry-After elapsed
  evidence: e000077, e000078, e000079, e000080
  -> wiretrail <file> rate-limit

Real output from a demo capture

A command-line tool

WireTrail has no window to click through. Each investigation is one command that prints a report you can read in a terminal, paste into a ticket, or parse with jq. To watch traffic live or edit and resend a request, use your browser's DevTools or a proxy.

What do you want to do?

  • Get a HAR

    Save a capture from Chrome, Edge, Firefox or Safari, or export one from a proxy or a phone. Check that it holds what the analysis needs.

    Capture

    Popular: From a browser · Handle captures safely

  • See what happened

    Start with a summary, let auto run the follow-ups, or ask diagnose for ranked findings with the evidence behind each.

    Analyze

    Popular: Summary · Auto · Diagnose

  • Find repeated calls

    Duplicates, retries, bursts, pagination loops, N+1 fan-out and ignored rate limits, and what differs between calls that look the same.

    Repeats

    Popular: Duplicates · Retries · Rate limits

  • Find what failed or was slow

    Errors with their messages, redirects, status changes, the slowest calls and what they were waiting for, expired tokens and token refreshes.

    Failures

    Popular: Errors · Slowest calls · Auth failures and refresh

  • Look inside one request

    Read one entry with secrets masked, search or extract from bodies, replay a call as curl, and write a report or a hand-off for another team.

    Inspect

    Popular: Show an entry · curl · Handoff

  • Catch a regression

    Compare a capture with a known-good one, enforce your own rules, and fail a build when the change is serious enough.

    Compare

    Popular: Compare against a baseline · Rules

  • Script it or hand it to an agent

    A stable JSON envelope, exit codes you can gate on, flat NDJSON and CSV exports, and a Claude Code plugin that runs the whole triage.

    Automate

    Popular: JSON output · Gate a build

  • Understand the findings

    How a HAR is read, how endpoints are grouped, what redaction does and does not do, and how findings are ranked.

    Concepts

    Popular: How redaction works · How findings are ranked

  • Look something up

    Every command and flag, the JSON fields, error messages and exit codes, measured speed, and what WireTrail cannot tell you.

    Reference

    Popular: Command line · Limitations

New here?

  1. Install WireTrail with cargo install wiretrail or a prebuilt binary.
  2. Work through Your first triage, a real investigation from the first summary to the call that causes the trouble.
  3. Keep Choose the right command open: it maps the question you have to the command that answers it.

No capture of your own yet? Follow along with the demo captures, which you can download and run every command on.

When to use WireTrail, and when not to

Reach for WireTrail when… Reach for DevTools or a proxy when…
You have a finished capture and a question about it. You want to watch traffic as it happens.
The capture is large, or the machine is a CI runner or a remote box. You want to edit a request and send it again.
An agent or a pipeline should read the result. You are exploring with no question yet.

The two work well together. Capture in the browser or a proxy, then run WireTrail on the exported .har file. Use the search box (press S or /) to find a command, a flag or an error message.

Get help and follow changes

Read what changed in each release in What's new, or on the GitHub releases page. If a step in this guide differs from your build, report it on GitHub with your WireTrail version (wiretrail --version), your operating system and the command you ran.