Why Append '?v=1' to CSS and JavaScript URLs?

Appending "?v=1" to CSS and JavaScript URLs: Enhancing Performance and Ensuring Updates

In HTML5 boilerplate templates, you may have noticed the use of "?v=1" appended to CSS and JavaScript URLs. This small query string serves a significant purpose in improving browser performance and ensuring that visitors always get the latest version of your assets.

What it Does

When you append "?v=1" to a file URL, you essentially force the browser to check for a new version of that file before loading it from the cache. This is important because most browsers tend to cache static assets like CSS and JavaScript files aggressively, which can lead to outdated versions being used even after changes have been made on the server. By appending a version number to the URL, you break the caching mechanism and force the browser to retrieve the latest version from the server.

Selective Use on JavaScript URLs

You may have noticed that not all JavaScript URLs in the sample provided have the "?v=1" query string. This is because, in some cases, it is not necessary. If a JavaScript file includes vendor prefixes or contains non-critical code, such as a polyfill, then it may not need to be updated as frequently as other files. By omitting the version number for these files, you can reduce the number of requests made to the server and improve performance.

Leveraging File Hashing

Instead of using a fixed version number, some websites opt to use a file hash in the query string. This approach is even more effective as it ensures that the browser only fetches a new version of the file if the actual content of the file has changed.

Additional Benefits

Apart from enforcing updates, appending a version number or file hash to asset URLs also allows you to set long cache headers without worrying about outdated content being served. Browsers will always treat it as a different file and prioritize fetching the latest version.

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