Directive: base uri

Overview

The base-uri directive restricts the URLs that can be used to specify the document's base element.

Affects: <base>

Required reading:

• Can I use base-uri?
• MDN Web Docs reference

Usage examples

Accepts one or more schemes or hosts, the 'self' keyword, or the 'none' keyword.

base-uri 'none'

base-uri 'self'

base-uri example.com

base-uri example.com example.org

base-uri https://*.example.com

base-uri https:

Fallbacks

❌ base-uri does not fallback to default-src.

Possible errors

• CSP-0100 — [ERROR] directive %s has an invalid value %s

For developers

ABNF (CSP3)

directive-name  = "base-uri"
directive-value = serialized-source-list

See ABNF: serialized-source-list

Type

• source-list in CSP2
• serialized-source-list in CSP3

References

• CSP Level 2 reference
• CSP Level 3 reference
• MDN Web Docs reference
• HTML <base> element
• Can I use base-uri?