CSP: prefetch-src
Deprecated: This feature is no longer recommended. Though some browsers might still support it, it may have already been removed from the relevant web standards, may be in the process of being dropped, or may only be kept for compatibility purposes. Avoid using it, and update existing code if possible; see the compatibility table at the bottom of this page to guide your decision. Be aware that this feature may cease to work at any time.
Non-standard: This feature is non-standard and is not on a standards track. Do not use it on production sites facing the Web: it will not work for every user. There may also be large incompatibilities between implementations and the behavior may change in the future.
The HTTP Content-Security-Policy (CSP)
prefetch-src directive specifies valid resources that may
be prefetched or prerendered.
| CSP version | 3 |
|---|---|
| Directive type | Fetch directive |
default-src fallback |
Yes. If this directive is absent, the user agent will look for the
default-src directive.
|
Syntax
Content-Security-Policy: prefetch-src 'none';
Content-Security-Policy: prefetch-src <source-expression-list>;
This directive may have one of the following values:
'none'-
No resources of this type may be loaded. The single quotes are mandatory.
<source-expression-list>-
A space-separated list of source expression values. Resources of this type may be loaded if they match any of the given source expressions.
Source expressions are specified as keyword values or URL patterns: the syntax for each source expression is given in CSP Source Values.
Example
Prefetch resources do not match header
Given a page with the following Content Security Policy:
Content-Security-Policy: prefetch-src https://example.com/
Fetches for the following code will return network errors, as the URLs provided do not
match prefetch-src's source list:
<link rel="prefetch" href="https://example.org/" />
<link rel="prerender" href="https://example.org/" />
Specifications
No specification found
No specification data found for http.headers.Content-Security-Policy.prefetch-src.
Check for problems with this page or contribute a missing spec_url to mdn/browser-compat-data. Also make sure the specification is included in w3c/browser-specs.
Browser compatibility
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