Absolute CacheBust is a free extension for Magento 2 that ensures your visitors are viewing the latest version of your images, CSS and JavaScript files.
If you are using a CDN it can be used to effectively invalidate your CDN cache instantly. This extension will also bust any local versions of assets your visitors may have stored in their web browser cache. The extension can be installed via Packagist with Composer, and the source code is available on GitHub.
After some basic Web Server configuration the URL of your assets will include a new dynamic portion, eg. http://absolutecommerce.co.uk/static/version12345/some-stylesheet.css.
When you make changes to your images, JavaScript, CSS, etc., rather than waiting for your customers browser cache to expire, with this extension it is possible to immediately 'bust' the cache by automatically updating the /version12345/ segment of the URL. If this segment becomes /version54321/, your visitors browser or the CDN will treat it as a brand new request that it does not have cached, so will be forced to download the latest version..
Magento 2 already has some functionality to bust cache for static files with the 'Sign Static Files' setting. The Absolute CacheBust extension provides this same functionality and more: