title: $utils description: Helper functions: ungzip, and geoip / ipasn / ipaso.

$utils provides small helper functions for capture rule scripts. It is available only inside capture rule scripts.

#ungzip

$utils.ungzip(data: Uint8Array): Uint8Array

Decompresses gzip data and returns the result as a Uint8Array. If the input is not valid gzip, the original bytes are returned unchanged.

Response bodies are already decompressed by the capture engine when the response declares Content-Encoding: gzip, so you only need ungzip for data that is gzip-compressed at the application layer (for example a gzip blob embedded inside a field). Enable Binary Body on the rule so that body is exposed as a Uint8Array.

// Response rule with Requires Body + Binary Body on.
const plain = $utils.ungzip($response.body)   // Uint8Array
const text = new TextDecoder().decode(plain)
console.log(text)
$done({})

#geoip / ipasn / ipaso

$utils.geoip(ip: string): string | null
$utils.ipasn(ip: string): string | null
$utils.ipaso(ip: string): string | null

These look up the country (ISO 3166 code), the autonomous system number, and the autonomous system organization for an IP address.

These functions currently return null — IP geolocation data is not bundled. They are provided so that scripts referencing them do not fail; treat a null result as "unknown".