Dries Buytaert

Explanation

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.

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.
frame-ancestors defines what parents may embed a page using <frame>, <iframe>, <object>, <embed> or <applet>.
Notice Consider adding the upgrade-insecure-requests directive to automatically upgrade HTTP requests to HTTPS, helping to prevent mixed content issues.

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.

Specifies how the resource is transferred. Not to be confused with Content-Encoding which specifies how the request body is compressed. Transfer encoding operates at a lower level than content encoding.
chunked means that the data is send in chunks. Chunks are sent out and received independently of one another. The server can stream the document and does not have to wait for the full document to be generated. Similarly, the browser can start processing chunks as they come in rather than having to wait for the entire document to be downloaded.

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.