Caching Score: https://tafeqld.edu.au/content/dam/tafe/en/campaigns/fee-free/fft-2025-iris-web-1080x1080.jpg

What is this check, and why should you care

Having a cache hit ensures the fastest possible delivery of content to end users.

The response header X-Cache had a value of HIT.

Fastly has documentation on how to interpret the X-Cache header.

Maximum possible points

100

What is this check, and why should you care

Using a CDN is extremely useful for caching purposes.

Maximum possible points

50

What is this check, and why should you care

The time that it takes for a user's browser to receive the first byte of page content.

The lower the TTFB, the faster your site will be perceived by the end user.

To get maximum points, your TTFB must be less than or equal to 30ms. If your TTFB is more than 1 second then you get no points here.

Maximum possible points

50

What is this check, and why should you care

An ETag is an opaque identifier for a specific version of a resource, defined in RFC 9110 §8.8.3. When a client revisits a URL it can send the previously-seen value back in an If-None-Match request header (RFC 9110 §13.1.2); if the server still considers the response current it returns an empty 304 Not Modified instead of the full body, saving bandwidth and origin work.

An HTTP request with the request header If-None-Match with a value of "0x8DDEA85026A46FB" was sent, and an HTTP 304 was responded with.

See the Wikipedia page on ETag for more background.

To get maximum points, you need to have ETag identifiers and an HTTP 304 response must be received when using a valid If-None-Match request header.

Maximum possible points

30

What is this check, and why should you care

The Last-Modified response header carries the date the resource was last changed, defined in RFC 9110 §8.8.2. When a client revisits the URL it can send the previously-seen value back in an If-Modified-Since request header (RFC 9110 §13.1.3); if the resource has not changed the server returns an empty 304 Not Modified instead of the full body, saving bandwidth and origin work.

An HTTP request with the request header If-Modified-Since with a value of was sent, and an HTTP 304 was responded with.

Maximum possible points

30

What is this check, and why should you care

Having tiered caching can help improve the cache hit ratio of your site because it provides an additional layer of caching in front of your origin.

Maximum possible points

25

What is this check, and why should you care

A cached response is reusable for the duration of its freshness lifetime, defined in RFC 9111 §4.2. The freshness lifetime is taken from Cache-Control: s-maxage or max-age (§5.2), and falls back to the Expires header (§5.3) or a heuristic if neither is set. The longer the freshness lifetime, the higher the cache hit ratio at any given traffic level.

To get maximum points, your cache lifetime must be greater than or equal to 4 weeks. If your cache lifetime is less, then you will get some proportion of the score based on how close to 4 weeks you are.

The current cache lifetime is 3600 seconds (1 hour).

You can read more about which headers Fastly uses to indicate the cache lifetime.

Maximum possible points

100