Supported regular expression syntax in Amazon WAF - Amazon WAF, Amazon Firewall Manager, Amazon Shield Advanced, and Amazon Shield network security director
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Supported regular expression syntax in Amazon WAF

Amazon WAF supports the regular expression pattern syntax used by the PCRE library libpcre. The library is documented at PCRE - Perl Compatible Regular Expressions.

Amazon WAF doesn't support all constructs of the library. For example, it supports some zero-width assertions, but not all. We do not have comprehensive list of the constructs that are supported. However, if you provide a regex pattern that isn't valid or use unsupported constructs, the Amazon WAF API reports a failure.

Amazon WAF does not support the following PCRE patterns:

  • Backreferences and capturing subexpressions

  • Subroutine references and recursive patterns

  • Conditional patterns

  • Backtracking control verbs

  • The \C single-byte directive

  • The \R newline match directive

  • The \K start of match reset directive

  • Callouts and embedded code

  • Atomic grouping and possessive quantifiers