index.md

---

title: "CSP: style-src-elem"
slug: Web/HTTP/Headers/Content-Security-Policy/style-src-elem
browser-compat: http.headers.Content-Security-Policy.style-src-elem

---

{{HTTPSidebar}}

The HTTP {{HTTPHeader("Content-Security-Policy")}} (CSP) style-src-elem directive specifies valid sources for stylesheet {{HTMLElement("style")}} elements and {{HTMLElement("link")}} elements with rel="stylesheet".

The directive does not set valid sources for inline style attributes; these are set using {{CSP("style-src-attr")}} (and valid sources for all styles may be set with {{CSP("style-src")}}).

CSP version	3
Directive type	{{Glossary("Fetch directive")}}
{{CSP("default-src")}} fallback	Yes. If this directive is absent, the user agent will look for the {{CSP("style-src")}} directive, and if both of them are absent, fall back to default-src directive.

Syntax

One or more sources can be allowed for the style-src-elem policy:

Content-Security-Policy: style-src-elem <source>;
Content-Security-Policy: style-src-elem <source> <source>;

style-src-elem can be used in conjunction with {{CSP("style-src")}}:

Content-Security-Policy: style-src <source>;
Content-Security-Policy: style-src-elem <source>;

Sources

<source> can be any one of the values listed in CSP Source Values.

Note that this same set of values can be used in all {{Glossary("fetch directive", "fetch directives")}} (and a number of other directives).

Examples

Violation cases

Given this CSP header:

Content-Security-Policy: style-src-elem https://example.com/

…the following stylesheets are blocked and won't load:

<link href="https://not-example.com/styles/main.css" rel="stylesheet" />

<style>
  #inline-style {
    background: red;
  }
</style>

<style>
  @import url("https://not-example.com/styles/print.css") print;
</style>

…as well as styles loaded using the {{HTTPHeader("Link")}} header:

Link: <https://not-example.com/styles/stylesheet.css>;rel=stylesheet

Specifications

{{Specifications}}

Browser compatibility

{{Compat}}

See also

• {{HTTPHeader("Content-Security-Policy")}}

• {{CSP("style-src")}}

• {{CSP("style-src-attr")}}

• {{HTTPHeader("Link")}} header

• {{HTMLElement("style")}}, {{HTMLElement("link")}}

• {{cssxref("@import")}}

• {{domxref("CSSStyleSheet.insertRule()")}}

• {{domxref("CSSGroupingRule.insertRule()")}}

• {{domxref("CSSStyleDeclaration.cssText")}}