Dries Buytaert

Explanation

The Content Security Policy (CSP) header helps prevent cross-site scripting (XSS), clickjacking, and other code injection attacks by specifying which dynamic resources are allowed to load.
upgrade-insecure-requests instructs browsers to replace insecure URLs (HTTP) with secure URLs (HTTPS).

Allows web developers to debug content security policies. Violations are reported to the specified report-uri, but not enforced.

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.

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

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 date and time after which the page should be considered stale and all caches should be refreshed.
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.

private means the response can only be stored by the browser's cache, but not by CDNs, proxies, or any other shared caches.
max-age specifies the maximum amount of seconds a page is considered valid. The higher max-age, the longer a page can be cached.
Warning Because max-age is set to 0 seconds and no s-maxage is set, nothing will be cached in browsers or shared caches. Caching is effectively disabled!

The X-Content-Type-Options header, when set to nosniff, prevents MIME type sniffing. This enhances security by ensuring browsers respect the declared Content-Type of the response, mitigating MIME confusion attacks.
The value nosniff is correctly set, providing protection against MIME type sniffing attacks.

X-Frame-Options prevents this URL from being embedded in an iframe. This protects against clickjacking attacks.
sameorigin means that this page can be displayed in a iframe, but only on the currrent origin. It can't be displayed on another domain. Consider setting this to deny for added security.

This header enables the browser's built-in XSS protection. However, it's considered legacy and modern browsers may ignore it.
1 enables the browser's cross-site scripting (XSS) filtering.
mode=block instructs the browser to block the response if a XSS attack is detected, instead of sanitizing the page.

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=2592000 specifies that the alternative service information is fresh for 2592000 seconds.
ma=2592000 specifies that the alternative service information is fresh for 2592000 seconds.

Used by the server to advertise its support of partial HTTP requests. The browser can ask for a range or subset of the response body. It's a feature that allows a browser to resume an interrupted download. bytes is the only range unit currently supported. none means that the server does not support range requests.

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.

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