HAR file (H TTP Ar chive) is a special file format .har that stores the log of a web browser's interaction with the network.
Essentially, it is a record of all HTTP(S) requests and responses that occurred during the page load. It contains:
addresses of all resources (HTML, CSS, JS, images, API requests, etc.),
the execution time of each request,
headers,
request and response bodies (if enabled),
status codes (200, 404, 500, etc.),
information about redirects, cookies, caching.
Used for:
diagnosing website issues (slow loading, API errors),
analyzing traffic between the client and server,
reproducing or debugging errors in technical support,
security checks.
A HAR file can be captured in most browsers (Chrome, Firefox, Edge) via
DevTools → Network tab → Export HAR .
How to open a HAR file?
The easiest way is a text editor or code editor. But let's look at it in more detail.
The simplest ways
Any text editor (Notepad, VS Code, Sublime Text) - to see the "raw" data in JSON format.
Browser - Chrome, Firefox, Edge have built-in HAR viewers:Open DevTools → Network tab → drag the HAR file there, and it will display as a list of requests.
Convenient viewers
Google HAR Analyzer - a web service from Google for visualization. https://toolbox.googleapps.com/apps/har_analyzer/
HAR Viewer (online tools like harviewer.org).
Fiddler , Charles Proxy , Wireshark - professional network traffic analysis tools that support HAR import.
https://toolbox.googleapps.com/apps/har_analyzer/