Dries Buytaert

Explanation

The date and time at which the request was made. A browser uses it for age calculations rather than using its own internal date and time; e.g. when comparing against Max-Age or Expires.

The type of the message body, specified as a MIME type.

The Vary header specifies a list of headers that must be considered when caching responses. For a cached response to be used, these headers must match between the cached response and the new request. This ensures that the appropriate version of a resource is served based on factors like language, encoding, or device type.
Notice Varying on user-agent can lead to low cache efficiency due to the high number of unique user agents. Only use this if you're serving significantly different content based on user agent.

A cookie that was sent from the server to the browser.
expires= sets the maximum lifetime of the cookie using a specific date.
max-age= sets the maximum lifetime of the cookie in seconds.
domain= sets the domain to which the cookie will be sent.
path= indicates the path that must exist in the requested URL for the browser to send the cookie.

A cookie that was sent from the server to the browser.
expires= sets the maximum lifetime of the cookie using a specific date.
max-age= sets the maximum lifetime of the cookie in seconds.
domain= sets the domain to which the cookie will be sent.
path= indicates the path that must exist in the requested URL for the browser to send the cookie.

A cookie that was sent from the server to the browser.
path= indicates the path that must exist in the requested URL for the browser to send the cookie.

This Expires date is in the past: the page is considered stale and will be removed from all caches.
Notice Because there is a Cache-Control header with a max-age and/or s-maxage directive, the Expires header will be ignored. Consider removing Expires to save bandwidth and processing power.
PS: November 19th is my birthday! 🎂

no-cache means the response can be stored by any cache, but the stored response must be validated with the origin server before each reuse. If the origin confirms that the response hasn't changed, downloading of the full response body can be skipped.
Warning no-cache will cause a revalidation request to the origin server for every use of the cached response. Consider using public with appropriate max-age to improve caching efficiency.
Warning no-store means the response may not be stored in any cache, including the browser's cache.
must-revalidate indicates that once a page becomes stale, both shared caches and browser caches must not use their stale copy without validating it with the origin server first.
Notice It does not make sense to set must-revalidate with no-store; when nothing is cached, there is nothing to revalidate.
Notice It does not make sense to set must-revalidate with no-cache; must-revalidate is implied.
Notice no-store is set, so it does not make sense to set no-cache as well.

Warning The page can't be cached by any shared caches such as Varnish or a CDN. If the page is something everybody can access, this behavior is not desired.
Notice Pragma is a HTTP/1.0 header. This request uses HTTP/1.1. In HTTP/1.1, Pragma is deprecated and superseded by the Cache-Control header. Remove Pragma to save bandwidth and processing power.

Warning The dynamic status indicates that Cloudflare did not cache the requested HTML page, similar to a "cache miss". By default, Cloudflare caches static assets such as images, CSS, and JavaScript but excludes HTML due to its dynamic nature. To cache HTML content, change the 'Cache Level' setting from dynamic to cache everything in Cloudflare. This adjustment allows HTML pages to be cached, leveraging Cloudflare's global network for faster and more efficient content delivery.

This header is part of the Reporting API specification. They are used to configure the reporting of network errors and other issues to a specified endpoint.
The Report-To header specifies where reports should be sent.
group defines the reporting group. Groups allow reports to be grouped logically; e.g. there could be a group for network errors and a second group for browser feature deprecation reports.
max_age defines the number of seconds the browser should remember these settings. Prevents the browser from having to parse the JSON on each request.
endpoints defines one or more URLs where the reports need to be send to. Multiple URLs can be specified for failover and load-balancing. Endpoints can be assigned a weight to distribute load, with each endpoint receiving a specified fraction of the reporting traffic. Endpoints can also be assigned a priority to set up fallback collectors.

This header is part of the Reporting API specification. They are used to configure the reporting of network errors and other issues to a specified endpoint.
The NEL (Network Error Logging) header configures the reporting of network errors.
report_to defines the reporting group that reports for this NEL policy will be sent to. The reporting group details are specified in the Report-To header.
max_age defines the number of seconds the browser should remember these settings. Prevents the browser from having to parse the JSON on each request.
success_fraction defines the sampling rate that should be applied to reports about successful network requests. Its value must be a number between 0.0 and 1.0: 0 means no successful requests should be reported, and 1 means that every successful request should be reported.

The cf-ray header provides a unique identifier for each request through Cloudflare. It's useful for troubleshooting and tracking requests in Cloudflare logs.

The alt-svc header advertises alternative services for accessing the same resource, enabling protocol negotiation and potential performance improvements.
h3 indicates that HTTP/3 is supported. Variants like h3-29 refer to specific drafts of the HTTP/3 protocol.
ma=86400 specifies that the alternative service information is fresh for 86400 seconds.

Communicates one or more metrics for a given request-response cycle. Can includes metrics for CPU time, database read/writes, file system access, etc.

missing Add a Strict-Transport-Security header. The Strict-Transport-Security header or HSTS header is used to instruct browsers to only use HTTPS, instead of using HTTP. It helps enforce secure communication.

missing Add a Content-Security-Policy header. The Content-Security-Policy header helps browsers prevent cross site scripting (XSS) and data injection attacks.

missing Add a Referrer-Policy header. When a visitor navigates from one page to another, browsers often pass along referrer information. The Referrer-Policy header controls how much referrer information a browser can share. This is important to configure when private information is embedded in the path or query string and passed onto an external destination.

missing Add a Permissions-Policy header. Restrict access to device features like the camera, microphone, location, accelerometer and much more.

missing Add a Cross-Origin-Embedder-Policy to specify how this page can be loaded by cross-origin resources.

missing Add a Cross-Origin-Opener-Policy header to opt-in into better browser isolation.

missing Add a Cross-Origin-Resource-Policy header to specify who can load this page.

missing Add a X-Frame-Options header. The X-Frame-Options header prevents this URL from being embedded in an iframe. This protects against clickjacking attacks. Alternatively, set a Content-Security-Policy header with a frame-ancestor directive.

missing Add a X-Permitted-Cross-Domain-Policies header to prevent Flash, Adobe Reader and other clients from sharing data across domains.