Cache-Control Header

Table of Content

• Syntax
• Directives
• Examples
• Browser Compatibility
• How to modify Cache-Control header

The Cache-Control HTTP header is a crucial tool that controls how, or if, a network client caches the response. It allows a client or server to transmit several directives in its HTTP responses, which dictate the browser caching policies in both client and server-side. The directives are specific to each object in the response, allowing high customization and flexibility in the caching mechanism.

Syntax

Cache-Control: <directive>Copy

Where <directive> is the value of a specific caching directive.

Directives

1. Public: It defines the response can be cached by any cache, even if the response is usually non-cacheable or associates with HTTP authentication.

2. Private: This specifies that the response is specifically for a single user and must not be stored in a shared cache.

3. No-Cache: It forces caches to submit the request to the origin server for validation.

4. No-Store: The most strict directive, insisting that the response must not be cached.

Examples

• Cache-Control: no-cache, must-revalidate

• Cache-Control: max-age=3600

• Cache-Control: private, max-age=600

Browser Compatibility

How to modify Cache-Control header

ModHeader is an extension available for Google Chrome browsers that allows developers to customize HTTP request and response headers, which includes modifying the Cache-Control directives.

1. Install the ModHeader extension from the Chrome Web Store.
2. Once installed, click the ModHeader icon in the toolbar.
3. In the drop-down list, click the + icon, add Cache-Control in the header name input box, and fill your directive in value input. Like no-cache, must-revalidate.

With this, you've modified the Cache-Control header for your requests. It's useful when you want to control how resources are cached on a client or server or when testing different caching policies and analyzing their outcomes.