Caching Score: https://developer.digitalhealth.gov.au/sites/default/files/js/js_0R_hGPcv6nqqrqq27t2K_1XhzU-iqGY7Qz-Nmz0q5RA.js?scope=header&delta=0&language=en&theme=adha_radix6&include=eJyNkNEOgyAMRX9I5G2_Q65QJxEoKWxxfz_nSDaTxfnY9Nzc08JNMALnl4su9RGoo6UGn2bt5JYR-jZ2eIEOMpvIjvR-_LnNQiNJMZYDiyl2okidZSFtOWZOlGrp8elXKuF-DAyBbVNpzqOn4I5Db-Q7FMl5qFVP8E9pQ4-RDMFVkKddx6aqLKe6Jk5cdQ5dPzRAnlWZpWo

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

The Set-Cookie response header is defined by RFC 6265 and is the mechanism HTTP servers use to ask the client to remember state across requests.

Cookies are inherently per-user state, so most reverse proxies and CDNs treat any HTML response carrying a Set-Cookie as personalised and refuse to share it from cache. A single uncacheable HTML response is usually fine; a Set-Cookie on every page view defeats public caching for the whole site.

Maximum possible points

20

What is this check, and why should you care

Using a caching proxy is extremely useful for caching purposes.

Maximum possible points

50

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

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.

No ETag header was found in the response.

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.

No Last-Modified header was found in the response.

Maximum possible points

30

What is this check, and why should you care

HTTP 404 (Not Found) is one of the response status codes that RFC 9110 §15.1 marks as heuristically cacheable, and RFC 9111 §4.2.2 defines the heuristic-freshness rules a cache may apply when no explicit freshness is provided. Caching 404s — even briefly — offloads repeated probes (broken links, scanners, missing assets) from your origin.

To get maximum points, you need to have the ability to cache an HTTP 404 for any amount of time.

This check requested the URL https://developer.digitalhealth.gov.au/cachingscorebrokenurltest.

Maximum possible points

20

What is this check, and why should you care

HTTP compression reduces the size of a response body by eliminating redundancy. The client advertises supported algorithms in the Accept-Encoding request header, and the server reports which one it used in the Content-Encoding response header — both are defined in RFC 9110 §8.4.

The four common encodings each have their own specification: gzip (RFC 1952), deflate (RFC 1951), br / Brotli (RFC 7932), and zstd / Zstandard (RFC 8878). Smaller responses load faster and use less bandwidth, which especially matters on mobile networks.

No Content-Encoding header was found in the response.

See the Wikipedia page on HTTP compression for more background.

To get maximum points, you need to use Brotli or Zstandard compression.

Maximum possible points

20