Rules

Rules match traffic and apply one or more actions before PostGate forwards a request or returns its response. The syntax follows the familiar Whistle rule format:

Text
pattern action [action ...] [filter ...]

For example:

Text
api.example.com host://127.0.0.1:3000 reqHeaders://x-postgate=local

Rule groups

Rules live in named groups. A group must be enabled before its rules enter the proxy pipeline. Groups can be created, renamed, reordered, and disabled without deleting their content.

The editor parses changes as you type. Errors prevent invalid rules from running, while warnings identify protocols that PostGate recognizes but cannot apply.

Comments and multiple actions

Lines beginning with # are comments. Put additional actions on the same line:

Text
# route locally, add a header, and slow the responseapi.example.com host://localhost:3000 reqHeaders://x-env=local resDelay://250

Values

Large JSON, HTML, JavaScript, or header maps do not need to fit on a single rule line. Save reusable content in Values and reference it from a compatible action. Rules can also load local files, external rule files, and response bodies from HTTP(S) resources.

Compatibility

PostGate targets Whistle v2.10.6 syntax, but it does not reproduce every Whistle runtime behavior. Review Compatibility before migrating a large ruleset.