You are browsing the docs for the snapshot version of Nexus, the latest release is available here
Conditional requests
Nexus Delta supports conditional requests as defined here for the different operations: * Fetch operation for the different types of resource * Fetch original payloads for the different types of resources * Fetching the file contents
The response for those operations are augmented with a ETag response header.
The client can then use this value to set up caches and save bandwidth by using the conditional headers as Delta can immediately answer with a 304 Not Modified and not resend the full response.
Nexus will return different etags for the same resource depending on the Accept header (more about content negotiation here) and the Accept-Encoding header.