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Supported Kong Router Flavors

Kong Gateway (open-source and enterprise edition) includes an expression-based router in versions 3.0 and later. The router can be configured in the following modes:

• traditional: uses the pre-3.0 router.
• traditional_compatible: uses the expression based router, but the router configuration interface remains the same as traditional.
• expressions: uses the expression-based router, and expressions must be provided in the router configuration interface.

The compatibilities of router flavors between different Kong Ingress Controller versions and Kong Gateway are shown in the following table. Kong Ingress Controller in versions 2.6.x and lower does not support Kong Gateway 3.0 and later, so the version of Kong Ingress Controller begins at 2.7.x.

Kong Ingress Controller	2.7.x	2.8.x	2.9.x	2.10.x
Kong 3.x traditional
Kong 3.x traditional_compatible	(1)	(1)	(1)	(1)
Kong 3.x expressions				(2)

(1) Most use cases are supported. The incompatible cases comes from the difference of regular expression standards in different routers: traditional router accepts PCRE 2 regular expressions, but traditional_compatible and expressions routers accepts regular expression in Rust. The most significant difference is that Regular expressions with a backslash (\) followed by a non-escaped character (for example, \j or \/) in matches of paths or headers are accepted in traditional router but not accepted when Kong Gateway 3.x is configured to use the traditional_compatible router.

(2) Limited support of expression based router (alpha maturity). Please refer to expression router concept page to see detailed status of supporting Kong Gateway with expression router.