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Reduce the number of domains serving resources

Identifiers

GreenIT V2 V3 V4
170 55 18

Categories

Life cycle Tiers Responsible
4. Production Network Software Architect/Developer

Indications

Priority Implementation difficulty Ecological impact
3 3 4
Saved resources
Queries

Description

When a website or online service hosts web pages components on multiple domains, HTTP connection must be established with each of these domains by the browser. Once the HTML page is received, the browser fetch resources while going through the DOM (Document Object Model). Some resources are essential for the web page to work. If they are hosted on unresponsive domains, the page can become slower. When possible, all resources should be grouped together on a single domain.

The only exception to this rule would be the hosting of static resources (stylesheets, images, etc.) on a dedicated domain to avoid the upload of one or more cookies for each HTTP GET by the browser. Response time will decrease as well as unnecessarily consumed bandwidth.

Example

For an institutional website with high traffic, two subdomains should be preferred:

  • application server on www.domain.tld
  • “cookie-less” media server on media.domain.tld

This reduces the number of domains and avoids needlessly transporting cookies with each HTTP GET request on static resources.

Validation rule

The number of ... is equal to or less than
domains serving resources 5