HAR File - What is it & How to Generate One

When it comes to understanding the complexities of web performance and troubleshooting issues, HAR files stand as a pivotal tool for developers and technical support teams. HAR, which stands for HTTP Archive, is a file format used for tracking all the interactions a browser makes with a website.

In this comprehensive guide, we’ll delve into what HAR files are, and their importance, and provide a step-by-step process on how to generate one across various popular browsers like Chrome, Firefox, Safari, and Edge.

What is a HAR File?

A HAR file is a JSON-formatted log of a web browser’s interactions with a site.

It records all the requests sent and responses received, the time it took to get those responses, headers, cookies, and other details that are crucial for detailed analysis. By examining a HAR file, one can pinpoint performance bottlenecks, identify network issues, and understand the behavior of web applications.

Why are HAR Files Important?

HAR files are invaluable for developers and IT professionals because they provide a granular view of each element’s loading sequence on a webpage. This can be particularly useful when:

• Diagnosing slow load times
• Debugging complex request and response cycles
• Analyzing the sequence of resource loading
• Identifying third-party services impacting performance

How to Generate a HAR File in Different Browsers?

Google Chrome

• Step 1Open Developer Tools

  Right-click anywhere on the page you want to analyze and select Inspect, or press Ctrl+Shift+I (Cmd+Option+I on Mac).

• Step 2Access the Network Tab

  Click on the Network tab in the Developer Tools panel.

• Step 3Record the Session

  
  

  Ensure the record button (the red circle at the top-left of the Network tab) is active. If it’s grey, click it to start recording.

  

• Step 4Replicate the Issue

  If it isn’t already, check the Preserve log box. Click the grey crossed-circle button to delete any existing logs from the Network tab. Refresh the page or perform the actions that lead to the issue you’re investigating.

• Step 5Save the HAR file

  Right-click anywhere on the grid of network requests, select Save all as HAR with content, and save the file to your desired location.

  

Mozilla Firefox

• Step 1Open Network Monitor

  Right-click anywhere on the page and select Inspect Element, then click on the Network tab or press Ctrl+Shift+E (Cmd+Option+E on Mac).

• Step 2Start Capturing Traffic

  The recording will start automatically when you open the Network Monitor.

• Step 3Replicate the Issue

  Refresh the page or perform the necessary actions to capture the traffic related to your problem.

• Step 4Export the HAR File

  Right-click anywhere on the grid of network requests, select Save All as HAR, and choose where to save the file.

  

Safari

• Step 1Enable the Develop Menu

  Go to Safari > Settings > Advanced and check the box at the bottom that says Show features for web developers.

  

• Step 2Open the Web Inspector

  Right-click anywhere on the page and Inspect Element, then click on the Network tab or press Cmd+Option+I.

• Step 3Replicate the problem

  Refresh the page or perform whatever actions are necessary to capture the traffic related to your problem.

• Step 4Export as HAR

  After you completed the steps that recreate the problem, click on the Export button at the top right of the Network tab and save the HAR file.

  

Microsoft Edge

• Step 1Access Developer Tools

  Right-click anywhere on the page and select Inspect or press F12 or Ctrl+Shift+I

• Step 2Navigate to the Network tab

  Click on the Network tab in the Developer Tools window.

  

• Step 3Record Network Activity

  Ensure the recording is active (red circle). If not, click it to start.

  

• Step 4Perform the Actions

  Refresh the page or replicate the steps that you need to troubleshoot.

• Step 5Save the HAR File

  Right-click within the list of network events and click Save all as HAR with content, then save the file.

  

Analyzing HAR Files

Once you have generated a HAR file, if you need to, you can analyze it using various online tools or by manually inspecting the JSON-formatted content. Look for long wait times, failed requests, or large files that could be optimized.

Conclusion

HAR files are a powerful resource for anyone looking to optimize website performance or troubleshoot issues. By following the steps outlined above, you can generate HAR files in Chrome, Firefox, Safari, and Edge, gaining valuable insights into the inner workings of web interactions.

FAQs

Can HAR files contain sensitive information?

Yes, HAR files can contain sensitive data such as personal details, cookies, and authentication tokens. It’s important to handle and share HAR files with caution, ensuring that they are only shared with trusted parties and are securely stored.

How can I view the contents of a HAR file?

You can view HAR files using various online tools like Google’s HAR Analyzer or software that can parse JSON format. These tools allow you to visualize the data in a more readable format.

Are HAR files used for performance testing?

While HAR files are not typically used for automated performance testing, they are an excellent resource for manual performance analysis and can help identify issues that may not be apparent during automated tests.

Can generating a HAR file affect website performance?

The process of generating a HAR file should not significantly affect website performance for the user. However, the Developer Tools can consume additional system resources on your computer, which might slightly slow down your browser or operating system.

Is it possible to edit a HAR file?

Yes, since HAR files are in JSON format, they can be edited with a text editor. However, editing a HAR file is not recommended unless you know exactly what changes you need to make, as it could corrupt the file or alter the recorded data.