This will evaluate the effectiveness of using a previous version of a file as a dictionary for brotli compression.
Given 2 URLs, one for the previous version of a file to use as a dictionary and one for the new version of a file, it will compress the new file with brotli compression using the previous version as an external dictionary (brotli -D) and compare the results to compressing the new file with brotli alone.
There is a version of this test for use with dynamic content (i.e. HTML) here.
The URLs to be tested will be fetched anonymously (no cookies) using the User Agent string of your current browser so they must be publicly available.
Please provide full URLs including the scheme (i.e. https://www.example.com/bundle.js?v=1)
If you do not have access to both versions of the file, the Internet Archive's Wayback machine can be useful for accessing previous versions (open a previous version of the page with dev tools open and observe the URLs requested).