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Validate a capture

validate checks whether a capture holds what the analysis needs. A capture can be valid HAR and still be nearly useless: a browser that was asked not to save bodies, an exporter that stripped the headers, a recording that started too late. validate tells you that before you trust an empty result.

wiretrail checkout.har validate

HAR 1.2 via WireTrail demo generator (synthetic)  (99 entries)
with timings: 99% · response bodies: 81% · POST req bodies: 100%
auth headers: true · cookies: true

anomalies:
  status-0: 1

The first line is the HAR version, the program that wrote the file, and the number of entries.

Line Meaning
with timings The share of entries that report a send, wait or receive time above zero. Slowest calls and Startup profile need these.
response bodies The share of entries with a response body. Errors, Search bodies and Extract a field need these.
POST req bodies Of the POST, PUT and PATCH requests, the share that has a request body. What varies between calls needs these.
auth headers, cookies Whether any request carries an Authorization or a Cookie header.
anomalies Entries that look broken, with a count.

The share with timings is 99%, not 100%, because one request has no send, wait or receive time. It is the failed image request, which spent 30 ms on dns and 1,870 ms on connect and then failed.

Anomalies

Anomaly Meaning
status-0 The request has status 0: it failed before a response arrived. This is often a real failure, not a defect in the file.
missing-method An entry with no HTTP method.
zero-duration-with-body A request with a response body and a duration of zero.
negative-size A body size below -1. HAR uses -1 for "unknown", so lower values are wrong.

validate exits 1 when it reports any anomaly, so a single failed request makes it exit 1. Use the exit code as "something to read", not "the file is broken".

A capture that has been stripped

Many tools remove credentials and bodies on export. validate recognizes that and says what is lost:

wiretrail sanitized.har validate

HAR 1.2 via WireTrail demo generator (synthetic, sanitized)  (99 entries)
with timings: 99% · response bodies: 0% · POST req bodies: 0%
auth headers: false · cookies: false
sanitized: yes (no auth/cookies and few response bodies)

anomalies:
  status-0: 1

sufficiency:
  - few/no response bodies captured — `errors`/`search`/`extract` limited
  - no Authorization headers — `auth`/`jwt` limited
  - no request bodies on POST/PUT/PATCH — `diff` body verdicts limited

sanitized: yes appears when there are no Authorization or Cookie headers and fewer than 10% of responses have a body. sufficiency is a separate list, and it does not depend on sanitized. It prints one note for each of four conditions that holds:

  • fewer than 10% of responses have a body: errors, search and extract are limited;
  • no request carries an Authorization header: auth and jwt are limited;
  • there are POST, PUT or PATCH requests and none has a body: diff body verdicts are limited;
  • no request has any send, wait or receive time: slowest and startup are limited.

The notes keep you from reading an empty jwt result as "no tokens". The analysis still runs on what is there.

JSON

wiretrail checkout.har validate --json | jq '.result | {pct_with_timings, pct_with_resp_body, sanitized, anomalies}'

{
  "pct_with_timings": 0.98989898989899,
  "pct_with_resp_body": 0.8080808080808081,
  "sanitized": false,
  "anomalies": [
    {
      "kind": "status-0",
      "count": 1
    }
  ]
}

The shares are fractions between 0 and 1 in JSON, and percentages in the text.