Dries Buytaert

Explanation

Specifies whether the network connection stays open after the current request. keep-alive specifies that the browser would like to keep the connection open, while close indicates that the browser wants to close the connection.

The size of the message body, in bytes.

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

private means the page can only be stored by the browser, but not by CDNs, Varnish or any other shared caches.
Warning no-store means the response may not be stored in any cache, including the browser's cache.
Notice no-store is set, so it does not make sense to set private as well.

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 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 compairing against Max-Age or Expires.

The Via header tracks how a page is forwarded from proxy to proxy. Beware, not all proxies append themselves to the Via header.

The Strict-Transport-Security header or HSTS header is used to instruct browsers to only use HTTPS, instead of using HTTP.
max-age is the time, in seconds, that the browser should remember to use HTTPS only.
includesubdomains instructs the browser that all subdomains are HTTPS-only as well.

Instructs the browser not to change the MIME type of the request. Browsers sometimes sniff or inspect the document to determine if the specified MIME type is correct. A browser changing the MIME type of a document can introduce security vulnerabilities. These vulnerabilities can occur when a website allows users to upload content and the user disguises a particular file type as something else. For example, a JavaScript file is uploaded as a JPEG file. When the browser changes the MIME type from image/jpeg to test/javascript, it gives attackers an opportunity to perform a cross-site scripting attack.

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.

1; mode=block enables the browser's cross-site scripting (XSS) filtering. Browsers that support X-Xss-Protection will stop rendering the page when an attack is detected.
Notice It is recommended to use Content-Security-Policy instead of X-XSS-Protection. Some browsers like Firefox refuse to support X-XSS-Protection. Content-Security-Policy is more advanced, a W3C recommendation, and supported by all modern browsers.

Some of the software used to generate or serve this page.

The Report-To header instructs the browser where to send "Network Error Logging" (NEL) reports to.
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.
include_subdomains is a boolean that enables or disables NEL reporting for subdomains of the origin.

The "Network Error Logging" (NEL) header is used to configure network request logging; enables websites and applications to receive reports about failed network fetches from supporting browsers.
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.
include_subdomains is a boolean that enables or disables NEL reporting for subdomains of the origin.
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.
failure_fraction defines the sampling rate that should be applied to reports about failed network requests. Its value must be a number between 0.0 and 1.0: 0 means no failed requests should be reported, and 1 means that every failed request should be reported.

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