How to open and analyse HAR files
Capture a HAR in Chrome, Edge or Firefox, inspect common errors, and export findings without uploading.
Mightora / Developer tools / Network diagnostics
Understand your HAR file.
Keep it on your device.
Find the requests, errors and network delays slowing your application down. Free, open source, and processed entirely on your device.
🔒 Local analysis · No HAR uploads · No telemetry · Sanitised reports
Portable · No installation
Download the offline HAR analyser
Prefer to work without an internet connection? Download one self-contained HTML file you can double-click on Windows, macOS or Linux. All code, styling and the Mightora logo are embedded. No account, server, installation or external assets are required.
Important: This is an HTML file, not an executable program. Unzip it and open har-analyser.html in your browser. The raw HAR still contains secrets, so handle the original file carefully.
Analyse an HTTP Archive
Select a .har file up to 50 MB. Its contents are parsed in a dedicated browser worker, not sent to a server.
No HAR data loaded.
Privacy notice: Raw HARs can contain passwords, cookies, tokens, private URLs and response bodies. Never share an original HAR without reviewing it. Sanitised reports may still identify services by hostname or path.
Analysis dashboard
Top hosts by cumulative duration
Potential problems
Requests — slowest first
| Method | Status | Sanitised URL | Duration | Size | Wait |
|---|
Security & transparency
Verify the tool’s network activity
WEBSITE EDITION · LOCAL HAR PROCESSING
This website loads Mightora branding and other page assets. Your HAR is analysed locally and is not sent to an application server. Use the checks below to distinguish page resources from HAR uploads.
Browser-observed resource entries—
External origins observed—
Observed destinations
- Check when the page has loaded.
Scope: This display uses the browser’s Resource Timing API, showing resource loads exposed to this page since navigation. It does not capture every network request, the initial document, extensions, blocked attempts, or all browser background activity. It is not a security certification.
How to independently verify with F12 (Developer Tools)
- Open Developer Tools using F12 or Ctrl+Shift+I (Windows/Linux). On a Mac, press Command+Option+I or use the browser menu.
- Choose the Network tab, select All and enable Preserve log. The recording indicator should be active.
- Reload the page while the Network panel is open. Website assets such as the shared Mightora component scripts, styles, images and badge images may be requested.
- Choose a HAR file and run the analysis. Observe the Network panel. In particular, filter by Fetch/XHR to investigate any application requests and inspect their destinations.
- If you see unexpected requests, investigate the destination and payload before drawing conclusions. Disconnect from the internet and repeat with the offline edition when handling highly sensitive captures.
Privacy tip: DevTools itself may display sensitive URLs or header data from other sites. Do not share an unreviewed network export.
HAR troubleshooting resources
Explore practical guidance for identifying HTTP errors and performance issues. These guides explain what the measurements mean, how to interpret them, and what information a HAR can expose.
Understand HAR performance timings
Learn about DNS, connect, SSL, wait, P95, and why summed request durations aren't page load time.
How to analyse HAR files offline
Run a fully self-contained HTML application locally, even without an internet connection.
HAR privacy and safe sharing
Understand authentication data, cookies, sensitive response bodies and the limits of sanitised reports.
How to analyse a HAR file
A HTTP Archive (HAR) captures browser network requests, timings, and responses. In Edge or Chrome, open Developer Tools → Network, reproduce the issue, and export the network log as HAR. Treat that capture as confidential.
What this analyser detects
4xx and 5xx errors, requests taking more than three seconds, responses larger than one megabyte, server wait time, DNS and connection delays, transfer totals, and latency percentiles.
What we never do
No HAR uploads, traffic replay, captured URL fetches, execution of response content, browser storage, account registration or application analytics. Content is handled locally by a Web Worker.
Aggregate request durations are not page load duration, because network requests can occur concurrently. Timing estimates depend on the captured browser data.
Frequently asked questions
Will my HAR file be uploaded?
No. The analyser reads the file in a local Web Worker. Shared brand components may still load from external CDNs, so consider running a vetted offline copy for particularly sensitive captures.
Are my exports anonymous?
Not necessarily. Reports remove cookies, authentication headers, bodies, URL query strings and many identifying path segments, but hostnames and other path information can remain. Review before sharing.
Can I analyse a HAR file offline?
Yes. Download the ZIP, extract har-analyser.html, and open it directly from your computer. This edition includes its own styles, JavaScript and logo; it does not fetch external libraries.
What is a HAR file?
A HTTP Archive (HAR) is a JSON-based record of a browser's network requests and timings, often exported from Developer Tools to investigate slow webpages or failing APIs.
What causes slow requests in a HAR file?
Likely causes include DNS lookup, connection setup, TLS negotiation, server processing and large transfers. Compare timing components to determine where to investigate further.
How can I check which network requests this tool makes?
Open the Network Transparency section for an on-screen summary. For an independent check, press F12 (or Command+Option+I on macOS), select the browser’s Network panel, enable Preserve log, reload the page and analyse a HAR. The online website may load styling, logos and badges; captured HAR data is not uploaded by the analyser.
What does a slow server wait mean?
A high wait value can indicate application processing, network latency or upstream work before the first byte. Correlate findings with server logs for a definitive diagnosis.
Open-source quality and transparency
Review the source code and its automated test and security-scanning workflows. Badges link to live workflow evidence and do not imply security certification.
