* Skip to main content 
  * Skip to search 
  * Skip to select language 

[ MDN Web Docs  ](/en-US/) Open main menu

  * References  [ References ](/en-US/docs/Web)
    * [ Overview / Web Technology  Web technology reference for developers  ](/en-US/docs/Web)
    * [ HTML  Structure of content on the web  ](/en-US/docs/Web/HTML)
    * [ CSS  Code used to describe document style  ](/en-US/docs/Web/CSS)
    * [ JavaScript  General-purpose scripting language  ](/en-US/docs/Web/JavaScript)
    * [ HTTP  Protocol for transmitting web resources  ](/en-US/docs/Web/HTTP)
    * [ Web APIs  Interfaces for building web applications  ](/en-US/docs/Web/API)
    * [ Web Extensions  Developing extensions for web browsers  ](/en-US/docs/Mozilla/Add-ons/WebExtensions)
    * [ Web Technology  Web technology reference for developers  ](/en-US/docs/Web)
  * Guides  [ Guides ](/en-US/docs/Learn)
    * [ Overview / MDN Learning Area  Learn web development  ](/en-US/docs/Learn)
    * [ MDN Learning Area  Learn web development  ](/en-US/docs/Learn)
    * [ HTML  Learn to structure web content with HTML  ](/en-US/docs/Learn/HTML)
    * [ CSS  Learn to style content using CSS  ](/en-US/docs/Learn/CSS)
    * [ JavaScript  Learn to run scripts in the browser  ](/en-US/docs/Learn/JavaScript)
    * [ Accessibility  Learn to make the web accessible to all  ](/en-US/docs/Web/Accessibility)
  * Plus  [ Plus ](/en-US/plus)
    * [ Overview  A customized MDN experience  ](/en-US/plus)
    * [ AI Help (beta)  Get real-time assistance and support  ](/en-US/plus/ai-help)
    * [ Updates  All browser compatibility updates at a glance  ](/en-US/plus/updates)
    * [ Documentation  Learn how to use MDN Plus  ](/en-US/plus/docs/features/overview)
    * [ FAQ  Frequently asked questions about MDN Plus  ](/en-US/plus/docs/faq)
  * [ Curriculum  New  ](/en-US/curriculum/)
  * [ Blog ](/en-US/blog/)
  * [ Play ](/en-US/play)
  * [ AI Help  Beta  ](/en-US/plus/ai-help)

Search MDN  Clear search input  Search

Theme

  * [ Log in ](/users/fxa/login/authenticate/?next=%2Fen-US%2Fdocs%2FWeb%2FHTTP%2FHeaders%2FPermissions-Policy%2Fserial)
  * [ Sign up for free  ](/users/fxa/login/authenticate/?next=%2Fen-US%2Fdocs%2FWeb%2FHTTP%2FHeaders%2FPermissions-Policy%2Fserial)

  1. [ References  ](/en-US/docs/Web)
  2. [ HTTP  ](/en-US/docs/Web/HTTP)
  3. [ HTTP headers  ](/en-US/docs/Web/HTTP/Headers)
  4. [ Permissions-Policy  ](/en-US/docs/Web/HTTP/Headers/Permissions-Policy)
  5. [ Permissions-Policy: serial  ](/en-US/docs/Web/HTTP/Headers/Permissions-Policy/serial)

Filter sidebar  Clear filter input

##  In this article

  * Syntax 
  * Default policy 
  * Specifications 
  * Browser compatibility 
  * See also 

  1. [ HTTP ](/en-US/docs/Web/HTTP)
  2. Guides 
  3. Resources and URIs 
    1. [ Identifying resources on the Web ](/en-US/docs/Web/HTTP/Basics_of_HTTP/Identifying_resources_on_the_Web)
    2. [ Data URLs ](/en-US/docs/Web/HTTP/Basics_of_HTTP/Data_URLs)
    3. [ Introduction to MIME types ](/en-US/docs/Web/HTTP/Basics_of_HTTP/MIME_Types)
    4. [ Common MIME types ](/en-US/docs/Web/HTTP/Basics_of_HTTP/MIME_types/Common_types)
    5. [ Choosing between www and non-www URLs ](/en-US/docs/Web/HTTP/Basics_of_HTTP/Choosing_between_www_and_non-www_URLs)
  4. HTTP guide 
    1. [ Basics of HTTP ](/en-US/docs/Web/HTTP/Basics_of_HTTP)
    2. [ Overview of HTTP ](/en-US/docs/Web/HTTP/Overview)
    3. [ Evolution of HTTP ](/en-US/docs/Web/HTTP/Basics_of_HTTP/Evolution_of_HTTP)
    4. [ HTTP Messages ](/en-US/docs/Web/HTTP/Messages)
    5. [ A typical HTTP session ](/en-US/docs/Web/HTTP/Session)
    6. [ Connection management in HTTP/1.x ](/en-US/docs/Web/HTTP/Connection_management_in_HTTP_1.x)
    7. [ Protocol upgrade mechanism ](/en-US/docs/Web/HTTP/Protocol_upgrade_mechanism)
  5. HTTP security 
    1. [ Content Security Policy (CSP) ](/en-US/docs/Web/HTTP/CSP)
    2. [ HTTP Strict Transport Security (HSTS) ](/en-US/docs/Web/HTTP/Headers/Strict-Transport-Security)
    3. [