What are CloudFlare's Caching Levels?
You can set CloudFlare's CDN to cache static content according to these levels:
No Query String: Only delivers files from cache when there is no query string.
Ignore Query String: Delivers the same resource to everyone independent of the query string.
Standard: Delivers a different resource each time the query string changes.
We recommend using the Standard level.
Note: By default, CloudFlare does not cache HTML content. You can create a Page Rule to cache static HTML content.
Examples:
No Query String: example.com/pic.jpg
Ignore Query String: example.com/pic.jpg?ignore=this-query-string
Standard: example.com/pic.jpg?with=query