Request headers

Introduction

HTTP request headers are key-value pairs sent by a client (such as a web browser or API client) to a server as part of an HTTP request. These headers provide additional information about the request, helping the server understand how to process it. They can include details about the client, request type, accepted content, authentication, caching, and more.

Headers play a crucial role in web communication, enabling functionality such as content negotiation, security enforcement, and efficient data transfer. Below is a comprehensive list of commonly used HTTP request headers along with a brief description of their purpose.

Common request headers

Below is a table of common HTTP request headers and info about their usage:

Header Name	Description
Accept-Charset	Specifies the character sets the client can handle.
Accept-Encoding	Specifies the encoding methods the client can accept.
Accept-Language	Specifies the preferred languages for the response.
Accept	Specifies the media types the client can process.
Authorization	Contains credentials for authentication.
Cache-Control	Controls caching behavior of the request.
Connection	Specifies control options for the current connection.
Content-Length	Indicates the size of the request body in bytes.
Content-Type	Specifies the media type of the request body.
Cookie	Sends stored HTTP cookies to the server.
DNT (Do Not Track.md)	Indicates the user's tracking preference.
Expect	Specifies expected behavior from the server.
Forwarded	Contains information about a forwarded request by a proxy.
From	Provides an email address of the user making the request.
Sec-Gpc	Indicates the user's PII tracking preferences.
Host	Specifies the domain name of the server handling the request.
If-Match	Used for conditional requests based on ETag matching.
If-Modified-Since	Sends the last modification date to check for updates.
If-None-Match	Requests resources only if they do not match a given ETag.
If-Range	Requests a specific range of data if the entity remains unchanged.
If-Unmodified-Since	Requests resources only if they have not been modified.
Origin	Indicates the origin of the request for CORS purposes.
Pragma	Provides backward compatibility with HTTP/1.0 caches.
Priority	Specifies the priority of the request.
Proxy-Authorization	Contains credentials for authenticating with a proxy.
Range	Requests a specific byte range of a resource.
Referer	Specifies the referring webpage for the request.
Sec-Fetch-Dest	Indicates the destination of a requested resource.
Sec-Fetch-Mode	Indicates the request mode used when fetching a resource.
Sec-Fetch-Site	Indicates the context of the request's origin.
TE	Indicates supported transfer encodings.
Upgrade	Requests an upgrade to a different protocol.
User-Agent	Identifies the client software making the request.
Via	Provides information about intermediaries handling the request.
Warning	Sends additional information about the status of a request.