X-Cache-Hits

List indicating number of cache hits in each node.

Fastly writes this header into responses. It is proprietary to Fastly.

Fastly appends this non-standard header to responses by default, and sets it to the value of obj.hits.

The hit count is per-cache-server, not per-data-center, and cache hits will not be evenly distributed across cache nodes due to clustering.

This header may report results from multiple cache servers, if shielding is enabled.

You can remove this header, or make it subject to Fastly-Debug, by using VCL in the vcl_deliver subroutine:

if (!req.http.Fastly-Debug) {
  unset resp.http.X-Cache-Hits;
}