HAR File Viewer Online - TestMu AI (Formerly LambdaTest)

How to get a HAR file from your browser

An HTTP Archive (HAR) file captures all network requests loaded by a webpage, including stylesheets, scripts, API responses, images, and HTML. Follow these instructions to export a HAR log:

What Is a HAR File Viewer?

A HAR file viewer reads HTTP Archive (.har) files — JSON exports from a browser's Network tab — and renders them as an interactive list of requests with headers, payloads, cookies, query strings, and timing data. Instead of trying to parse a 50 MB JSON blob by hand, you load the HAR and get the same view your DevTools Network panel would show, including TTFB, DNS, TLS, and content-download breakdowns. This particular viewer runs entirely client-side, so HAR captures with sensitive auth tokens, cookies, or PII never leave your machine.

Why Use a HAR File Viewer?

Customers usually can't share their screen, but they can hit File > Save As HAR and send the file. The HAR viewer turns that file into a faithful, scrubbable record of what the user's browser saw — every request, every response, every timing phase. Support engineers use it to triage "slow page" complaints; backend teams use it to confirm whether an API really returned 200; QA teams use it to attach evidence to bug reports. Because the viewer mimics the DevTools Network tab, the mental model is already familiar to anyone who has debugged in the browser.

Key Features

• DevTools-style split view: request list on one side, full inspector on the other.
• Headers, payload, response, cookies, query strings, and timings — each in its own tab.
• Timing waterfall: blocked, DNS, connect, TLS, send, wait (TTFB), and receive phases per request.
• Status / method / type / URL filters for quickly narrowing thousands of requests.
• JSON pretty-printing for API responses, with collapsible nodes.
• Drag-and-drop file load or click-to-browse.
• Client-side only: nothing is uploaded, so auth tokens and cookies stay private.
• Works for HARs from Chrome, Edge, Brave, Firefox, and Safari.

Use Cases

• Customer-reported bugs: reproduce what the user's browser saw from a single attached file.
• API failures: confirm request URLs, payloads, and response status without screen-sharing.
• Performance triage: identify slow TTFB, blocked requests, or large payload culprits.
• Pre-release QA: compare HARs before/after a deploy to spot new third-party calls or regressions.
• Security review: audit what data, headers, and cookies a page sends to third parties.
• Vendor escalations: share evidence-rich HAR snippets with SaaS providers.
• Education & training: walk students through HTTP traffic with real-world captures.

Frequently Asked Questions

1. What is a HAR file?

A HAR (HTTP Archive) file is a JSON log of a browser session's network activity — every request, response, header, payload, cookie, and timing measurement, exported from the browser's DevTools.

2. Is the HAR file viewer free?

Yes. The tool is free, has no usage limits, and does not require an account.

3. Is my HAR file uploaded anywhere?

No. Parsing runs entirely in your browser. Your HAR — including any auth tokens or cookies inside it — stays on your machine.

4. How do I export a HAR from Chrome?

Press F12, open the Network tab, reload the page, and click the download icon at the top of the Network panel. Save the .har file to disk.

5. Does it work for Firefox or Safari HARs?

Yes. HAR is a standardised format, and the viewer accepts captures from Chrome, Edge, Brave, Firefox, and Safari.

6. Can I see request and response bodies?

Yes — when the HAR was captured with content enabled. JSON, HTML, and plain-text bodies are rendered in the inspector with pretty-printing for JSON.

7. Can I filter the request list?

Yes. Filter by HTTP method, status code, resource type, or URL substring to narrow a noisy capture to the requests that matter.

8. Will it show timings like TTFB?

Yes. Each request displays blocked, DNS, connect, TLS, send, wait (TTFB), and receive phases on a timing bar.

9. How big a HAR can it open?

It depends on your browser memory. Most laptops handle a few hundred megabytes; very large captures may pause briefly while parsing.

10. Why use this over opening the HAR in DevTools?

DevTools can re-import HARs, but the workflow is awkward. This viewer gives you a clean, dedicated UI you can share with non-engineers — no DevTools setup required.