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Revision 1132025 of Simple header

  • Revision slug: Glossary/Simple_header
  • Revision title: Simple header
  • Revision id: 1132025
  • Created:
  • Creator: teoli
  • Is current revision? Yes
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Revision Content

A simple header (or CORS-safelisted request header) is one of the following HTTP headers:

  • {{HTTPHeader("Accept")}},
  • {{HTTPHeader("Accept-Language")}},
  • {{HTTPHeader("Content-Language")}},
  • {{HTTPHeader("Content-Type")}} with a MIME type of its parsed value (ignoring parameters) of either application/x-www-form-urlencoded, multipart/form-data, or text/plain.

Or one of these client hint headers:

  • {{HTTPHeader("DPR")}}
  • {{HTTPHeader("Downlink")}}
  • {{HTTPHeader("Save-Data")}}
  • {{HTTPHeader("Viewport-Width")}}
  • {{HTTPHeader("Width")}}

When containing only simple headers, a requests is deemed simple and doesn't need to send a {{glossary("preflight request")}} in the context of CORS.

Learn more

  • HTTP headers
  • {{Glossary("Simple response header")}}
  • {{Glossary("Forbidden header name")}}
  • {{Glossary("Request header")}}

Revision Source

 
<p>A <dfn><em>simple header</em> (or </dfn><em>CORS-safelisted request header</em>) is one of the following <a href="/en-US/docs/Web/HTTP/Headers">HTTP headers</a>:</p>

<ul>
 <li>{{HTTPHeader("Accept")}},</li>
 <li>{{HTTPHeader("Accept-Language")}},</li>
 <li>{{HTTPHeader("Content-Language")}},</li>
 <li>{{HTTPHeader("Content-Type")}} with a MIME type of its parsed&nbsp;value (ignoring parameters) of either <code>application/x-www-form-urlencoded</code>, <code>multipart/form-data</code>, or <code>text/plain</code>.</li>
</ul>

<p>Or one of these client hint headers:</p>

<ul>
 <li>{{HTTPHeader("DPR")}}</li>
 <li>{{HTTPHeader("Downlink")}}</li>
 <li>{{HTTPHeader("Save-Data")}}</li>
 <li>{{HTTPHeader("Viewport-Width")}}</li>
 <li>{{HTTPHeader("Width")}}</li>
</ul>

<p>When containing only simple headers, a requests is deemed simple and doesn't need to send a {{glossary("preflight request")}} in the context of <a href="/en-US/docs/Glossary/CORS">CORS</a>.</p>

<h2 id="Learn_more">Learn more</h2>

<ul>
 <li><a href="/en-US/docs/Web/HTTP/Headers">HTTP headers</a></li>
 <li>{{Glossary("Simple response header")}}</li>
 <li>{{Glossary("Forbidden header name")}}</li>
 <li>{{Glossary("Request header")}}</li>
</ul>
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