What a HAR file actually is

A HAR file is a record of everything your browser did while loading a web page — every image it downloaded, every request it sent to a server, every response it got back. HAR stands for HTTP Archive. It is a plain text file that looks like code but is really just a list of events, saved with a .har extension.

You create a HAR file by opening your browser's developer tools, turning on recording, then visiting a website. When you stop recording, the browser saves all that activity into one file. Web developers and support teams ask for HAR files when something is broken — a page loads slowly, a payment form fails, a video won't play — because the file shows exactly what the browser tried to do and where it got stuck.

The file itself is human-readable if you open it in a text editor, but it is dense and hard to scan. That is why most people use a tool to open and display it instead.

Key Takeaways

  • A HAR file is a record of all network activity your browser performed while loading a website, saved as a single text file.
  • You can open a HAR file in any text editor, but a dedicated viewer tool makes the data much easier to read and search.
  • The most straightforward viewer is the one built into your browser's developer tools — no read or installation needed.
  • HAR files can contain sensitive information like passwords or authentication tokens, so only share them with people you trust or with official support channels.

Opening a HAR file in your browser's developer tools

The easiest way to view a HAR file is to use the tool that created it. Open your browser, press F12 (or right-click the page and select Inspect), then look for the Network tab. In most browsers, there is an import or open button near the top of the Network panel. Click it, select your .har file, and the browser will display all the recorded requests in an organized table.

In Chrome and Edge, the Network tab has a small circle icon with a downward arrow — that is the import button. In Firefox, look for the gear icon in the Network tab, then select Import HAR. Safari's developer tools also have an import option in the Network tab, though you may need to enable the developer menu first in Preferences.

Once imported, you can click on any request in the list to see details: what the browser asked for, what the server sent back, how long it took, whether it succeeded or failed. This view is much clearer than reading the raw file.

Opening a HAR file in a text editor

If you just need to look at the raw data, open the .har file with any text editor — Notepad on Windows, TextEdit on Mac, or any code editor like Visual Studio Code. The file will display as structured text with curly braces and square brackets. It is valid JSON, which is a standard format for storing data.

This approach is useful if you want to search for a specific word (like a URL or an error message) using the editor's find function. It is less useful if you want to understand the overall flow or compare request times, because the raw format is hard to scan.

Using an online HAR viewer

Several websites let you upload a HAR file and view it in a formatted display without installing anything. Popular options include HAR Viewer (hosted by the HTTP Archive project), Waterfall (a tool that shows request timing as a visual chart), and your browser's own developer tools viewer mentioned above.

To use an online viewer, visit the website, click the upload or open button, select your .har file, and the tool will parse it and display the data in columns and charts. Some viewers highlight slow requests or failed requests in red, making problems easier to spot.

The trade-off is that you are uploading your file to someone else's server. If the HAR file contains sensitive information — which it often does — use your browser's built-in viewer instead, which keeps the file on your computer.

What information is inside a HAR file

A HAR file contains the URL of every resource the browser requested, the size of each file, how long each request took, the HTTP status code (200 for success, 404 for not found, 500 for server error), and the response headers the server sent back. It also records cookies, authentication tokens, and sometimes the actual data sent in form submissions.

This is why HAR files are sensitive. If you log into a website, the HAR file may contain the session token that proves you are logged in. If you fill out a form with your address or payment information, that data is in the file. Before sharing a HAR file with anyone, check whether it contains information you would not want them to see.

Creating a HAR file yourself

To record a HAR file, open your browser's developer tools (F12), go to the Network tab, and look for a record button — usually a filled circle near the top left. Click it to start recording. Then navigate to the website or perform the action you want to record (load a page, submit a form, play a video). When you are done, right-click in the Network panel and select Save as HAR with Content, or look for an export button. Choose where to save the file and give it a name.

The file will be saved to your Downloads folder or wherever you chose. You can then send it to a developer or support team, or open it yourself using any of the methods above.

When to share a HAR file and when not to

Share a HAR file with official support channels — your bank's support team, a website's help desk, a software vendor — when they ask for one to troubleshoot a problem. They are trained to handle sensitive data and will not misuse it.

Do not share a HAR file in public forums, on social media, or with people you do not trust. Do not post it in a comment on a website or a public GitHub issue. If you must share it with someone outside an official channel, open the file in a text editor first, search for sensitive words like "password", "token", "credit", or "authorization", and delete those lines before sharing.

Frequently Asked Questions

Can I open a HAR file on my phone?

Most phones do not have a built-in HAR viewer. You can email the file to yourself and open it on a computer, or use an online viewer on your phone's browser — though this means uploading the file to someone else's server. For troubleshooting on mobile, most support teams will ask you to record the HAR file on a computer instead.

What if the HAR file is too large to open?

Very long browsing sessions can create HAR files that are hundreds of megabytes. Try opening it in a code editor rather than your browser, or use an online viewer that can handle large files. If it is still too large, record a shorter session — just the specific action that is broken — and create a new HAR file.

Does a HAR file show passwords?

It can. If you type a password into a form and submit it, the HAR file may record what you sent. This is why you should never share a HAR file publicly or with someone you do not trust. Always review the file in a text editor first and delete any lines containing passwords or personal information.

Can I edit a HAR file after I create it?

Yes, you can open it in a text editor and delete or change lines. However, if you remove data, the file may no longer be valid JSON, and some viewers will refuse to open it. If you need to remove sensitive information, delete only the specific lines that contain it, and test the file in a viewer afterward to make sure it still works.