Browser - Fetching Resources

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1 - About

Fetching is a web term that means getting a response from a request. The response includes generally a resource but it could also be empty.

User agents can implement a variety of transfer protocols to fetch resources such as:


3 - Processing Model

When a user agent is to fetch a resource or URL:

  • optionally from an origin,
  • optionally using a specific referrer source as an override referrer source,
  • and optionally with any of a synchronous flag, a manual redirect flag, a force same-origin flag, and a block cookies flag,

it must follow this processing model.

4 - Type

A web site (HTML, Javascript or CSS) can fetch two types of resources from a server:

4.1 - Data

A web site (HTML, Javascript or CSS) is able to receive data resources (such as HTML, XML, or JSON documents) from:


4.2 - Media

Media resources such as images, JavaScript, CSS, or fonts) can be included from any origin, even without permissive CORS headers.

Cross-Origin Read Blocking (CORB) prevents the fetch of a cross-origin data resource.

5 - Management

5.1 - Priority

5.2 - Type


5.3 - Origin

The origin request header indicates where a fetch originates from.

6 - Documentation / Reference