Get HTTP Header

Get HTTP Header is a tool designed to let you examine response headers sent from servers to clients, providing insight into how data is transmitted as well as which software was used for making requests.

Troubleshooting network events and investigating security concerns is made much simpler with an Nmap scanner, and its results can even identify specific browser versions running on specific operating systems.

Content-Length

Content-Length headers tell recipients of HTTP request or response what amount of data can be expected in an entity body, providing useful information for applications that need to allocate memory or anticipate downloads.

This header can be included with POST requests to inform the web server how large the body of an HTTP message is, and also used with GET requests to help clients anticipate its size and anticipate responses accordingly.

There are various general headers that can be added to requests and responses, offering additional details such as authentication credentials or caching policies. Connection and Cache-Control are two such headers.

Content-Encoding

An HTTP message's representation of an array of octets. It can help reduce transmission time by compressing message content; often used with Content-Type header.

Indicates the client-side encoding algorithm supported. Servers can use it to match request headers and determine whether responses can be cached.

IANA provides a list of official content encodings. However, malware transfers often use nonstandard encoding methods; so it is crucial that we understand these headers' nuances. ModHeader Chrome extension offers an effective means of customizing headers, which makes detecting malicious transfers much simpler. An internationalization checker from W3C also displays all encodings used on any given page.

Accept-Language

The Accept-Language request header identifies which natural languages a client prefers, along with their region. This is an integral component of Content Negotiation for REST APIs; however, its number of possible permutations can quickly become excessive and affect cache performance negatively if left unregulated.

Browsers typically set required values for their Accept-Language header based on their active user interface language, enabling servers to identify preferred languages and select suitable MIME types when sending responses.

Accept-Language header information can be an extremely effective tool for software localization, enabling websites and REST APIs to offer content tailored specifically for each user's preferred languages. However, it should be remembered that servers do not necessarily comply with this request, instead making decisions based on other criteria.

Accept-Parameters

The Accept-Parameters header contains metadata about how a resource is fetched or delivered, as well as instructions to the server on how it should format or personalize responses.

Example: It could indicate which media types it can understand during requests. As a response, the server could use content negotiation to select an acceptable representation before notifying its client using Content-Type header field.

User preferences may include whether they seek privacy or personalized content. For example, Chrome browsers' Save-Data header allows developers to deliver lighter and faster applications that have enabled data saving mode. When calling get() method with name as argument for each header name to retrieve values for all these requests.

Accept-Extension

The Accept-Extension HTTP header allows a server to provide additional information to its clients, such as entity tags. It also specifies how a request should be processed; content negotiation algorithms often utilize this header. As it's an end-to-end header, intermediary proxies shouldn't retransmit it.

This header can help prevent your browser from making repeated requests to the same webpage, which can slow the loading speed. Furthermore, it instructs your browser not to store this information in its cache memory; this can improve browsing experiences but does not guarantee that all pages won't still be stored locally on disk by your browser.

Allows you to set preferences for how the server processes requests, oftentimes losing these preferences when going through a proxy or load balancer.

Cache-Control

The Cache-Control request header enables websites to customize their caching behavior with directives such as max-age or no-cache. It may also be set both during requests and responses.

Cache-Control is a key-value pair wherein the key (on the left) always corresponds with "cache-control", and on the right can contain one or more directives comma separated with a colon ('/').

Cache-Control directives are taken into account by both an end-user's browser as well as any intermediate proxies. A browser uses ETag response headers to determine when resources have changed, thus prompting revalidation requests - however a browser with an overly aggressive max-age might trigger unnecessary requests for resources that remain unchanged; hence the Cache-Control directives play an integral part in controlling cache behavior on both client side and proxy level.

Content-Type

Content-type headers inform clients how to understand a web server's response, by identifying what data type is being sent by browsers and search engine bots correctly interpreting it. They're essential to the successful operation of websites; audio/mpeg tells browsers audio files must be opened with particular programs while application/javascript alerts them that server-side Java Script files have been sent from servers.

Although HTTP does not mandate Content-Type headers with GET requests, they are highly recommended to ensure the recipient receives correct data and reduce risk associated with MIME sniffing (see below). For further assistance in checking content types see SEOmator's free HTTP Header & Status Code Checker which allows users to see all headers including content types in real time.