Question

Does anyone know how exactly the asset digest value is calculated? If I have two JS files which contain various other included JS scripts then will each file maintain the same digest hash if none of the inner scripts have been changed? Or is a new digest value calculated each time the assets:precompile operation is run?

Answer 1

Grabbed from rails guides

When a filename is unique and based on its content, HTTP headers can
be set to encourage caches everywhere (whether at CDNs, at ISPs, in
networking equipment, or in web browsers) to keep their own copy of
the content. When the content is updated, the fingerprint will change.
This will cause the remote clients to request a new copy of the
content. This is generally known as cache busting.

The technique that Rails uses for fingerprinting is to insert a hash
of the content into the name, usually at the end. For example a CSS
file global.css could be renamed with an MD5 digest of its contents