HAR File Analyzer: Free Online HAR Performance Inspector — How-To Guide

A HAR file is a JSON recording of everything your browser loaded while a page was open — every request, response, status code, byte count, and timing detail. Developers capture them to debug slow pages, flaky APIs, and redirect chains. The problem is that a raw HAR file is thousands of lines of JSON that no human wants to read.

ToolsFam's HAR File Analyzer turns that JSON into a clear, readable summary: which requests were slow, which status codes came back, how many bytes each request moved, and where the timing bottlenecks are. Paste your HAR JSON, run the analysis, and get findings you can copy or download. No account, no upload — it runs locally in your browser.

Try it free: HAR File Analyzer

How to use it: step by step

1. Capture a HAR file

In Chrome or Edge, open DevTools (F12), go to the Network tab, reload the page with recording on, then right-click any request and choose Save all as HAR. Firefox offers a similar "Save All As HAR" option. Save the file somewhere handy.

2. Open the analyzer and load your input

Open the HAR File Analyzer page. Paste the contents of your HAR file into the input area. If you don't have a HAR file yet, load the built-in sample input first to see what the analysis looks like.

3. Validate and run the analysis

Run the tool's validation to make sure your JSON is a well-formed HAR file, then run the analyzer. It parses the entries and produces a readable breakdown: slow requests, status codes, transferred bytes, and timing bottlenecks.

4. Read the findings

Scan the results for the three things that matter most on a slow page:

• Slow requests — entries with the longest total or waiting time, often API calls or unoptimized assets.
• Status codes — anything that isn't a 200 (redirects, 404s, 500s) worth investigating.
• Heavy transfers — requests moving the most bytes; these are your compression and caching candidates.

5. Copy, download, or reset

Copy the findings into a bug report or download them as a text report to share with your team. When you're done, reset the tool to clear the input and analyze another file.

3 practical tips

Sanitize before you share. HAR files can contain cookies, authorization headers, and query-string tokens. Strip or redact sensitive values before pasting a HAR into any analyzer — including this one — especially if you'll share the report.

Record the right scenario. For a realistic first-visit profile, record with the browser cache disabled (DevTools has a "Disable cache" checkbox). Compare a cold load against a repeat visit to see what your caching actually saves.

Fix the biggest bytes first. One 2 MB hero image usually matters more than ten small CSS files. Sort the findings by transferred bytes to find the single asset worth compressing or lazy-loading.

FAQ

What is a HAR file?

HAR stands for HTTP Archive. It's a JSON file that records every network request a browser made while loading a page, with timings, headers, sizes, and status codes. All major browsers can export one from their developer tools.

Does the analyzer upload my HAR file?

No. The normal workflow runs locally in your browser, and no account is required. Your input stays on your device.

Can it read HAR files from any browser?

Yes. HAR is a standard JSON format, so files exported from Chrome, Edge, Firefox, or Safari all work the same way.

I found a slow request — what next?

Check whether the time went to waiting (server or API latency) or downloading (large response). Waiting time points at the backend; download time points at response size. Then fix the right side.

Privacy note

The HAR File Analyzer runs 100% in your browser. Your HAR file — which can contain session cookies and other sensitive data — is never uploaded anywhere. What you paste stays on your device.