Most modern web browsers include web development tools that developers and interested users may utilize for a variety of purposes. One of the useful applications that browser makers like Google, Mozilla and Microsoft added to the web development tools of their browsers is the ability to create so-called HAR files.
In this guide, we will explain what HAR files are, how they are created in popular web browsers, and how they can be used by developers to analyze website issues.
HAR, which stands for HTTP Archive format, is a log that details a web browser's interaction with a webpage. The log uses the JSON -- JavaScript Object Notation -- format
The HTTP Archive (HAR) format draft, published on August 14, 2012, provides the following definition:
This specification defines an archival format for HTTP transactions that can be used by a web browser to export detailed performance data about web pages it loads.
The document has since been abandoned, but HAR is supported by many modern browsers including Google Chrome, Mozilla Firefox, Internet Explorer and tools such as Fiddler.
The extension of HAR files is .har. The files can be opened in any web browser, specialized viewer applications designed for .har files, any JSON viewer application or extension, and also any text editor.
The purpose of HAR files is to create a record of activity when the browser connects to a site. The file includes information about the resources that are loaded, cookies, downloaded content, and lots of connection details.
Har files include webpage connection and loading information; one of the main applications is the analysis of site issues, e.g. when a site fails to load correctly in a browser or all browsers.
Web developers may view the output of the HAR file to find potential issues; the files are extremely useful when the developer cannot replicate issues.
Anyone can create a HAR file using web developer tools and send the file to the developer after its creation for analysis.
Generally speaking, it is necessary to open the Network Tools of the Developer Tools of the browser that is being used, load the site in question (or part of it depending on the issue), and use a save option to save the recorded data as a HAR file.
The same method works in most Chromium-based web browsers including Brave, Opera, Vivaldi or Microsoft Edge.
HAR files can be loaded in most browsers that support creating them. You find import HAR file options under Network in those browsers, and may use the imported data to analyze potential site issues.
Other tools exist, such as the online HAR file viewer.
Ghacks is a technology news blog that was founded in 2005 by Martin Brinkmann. It has since then become one of the most popular tech news sites on the Internet with five authors and regular contributions from freelance writers.
Thanks a lot for this useful article Martin. :D
as a performance engineer, I use HAR all the time :)