Browser - Fetching Resources (Request/Response)


Fetching is a web term that means:

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:

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.


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


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


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.






The origin request header indicates where a fetch originates from.


  • Swr React Hook :
    • - stale-while-revalidate with a HTTP cache invalidation strategy popularized by RFC 5861 - SWR first returns the data from cache (stale), then sends the fetch request (revalidate), and finally comes with the up-to-date data again.

Documentation / Reference

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