.HAR

Introduction

A HAR file records what a web browser fetched while loading pages: every request and response, with headers, cookies, bodies and timings. Browsers’ developer tools save one from their Network panel, and support teams often ask for a HAR file to see why a site misbehaves.

A HAR file is JSON. Because it holds cookies, sign-in tokens and form data as they were sent, it should be treated as secret and cleaned before it is shared.

Structure

The top-level object has one member, log. It holds the format version (usually 1.2), a creator naming the program that wrote it, an optional browser, a list of pages with their titles and load timings, and a list of entries, one per request.

Each entry gives the time the request started, its total time, the request (method, URL, HTTP version, headers, cookies, query string and any posted data), the response (status, headers, cookies, and the body under content, as text or base64), cache details, and timings broken into blocked, DNS, connect, SSL, send, wait and receive, in milliseconds.

{
  "log": {
    "version": "1.2",
    "creator": { "name": "…", "version": "…" },
    "pages": [ … ],
    "entries": [
      { "startedDateTime": "…", "time": 120,
        "request": { … }, "response": { … },
        "cache": { }, "timings": { … } }
    ]
  }
}

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