Query Param Extractor - Server-Side Google Tag Manager Variable

The Query Param Extractor is a Server-Side GTM variable template that extracts the value of a named query parameter from a URL or path string.

Features

• Accepts full URLs (e.g. https://example.com/path?foo=bar) and path-only strings (e.g. /path.php?foo=bar).
• Extracts a single named query parameter by key.
• Automatically URL-decodes the extracted value.
• Returns undefined cleanly when the input is missing, has no query string, or the parameter is not found.
• Handles edge cases such as keys without values and values containing = characters.

Getting Started

1. Add the Query Param Extractor variable to your GTM Server container.
2. Set the URL or Path Input field — this can be any variable that resolves to a URL or path string (e.g. a request URL variable).
3. Set the Query param to extract field to the exact parameter key you want (e.g. utm_source, gclid, session_id).
4. The variable will return the decoded value of that parameter, or undefined if it is not present.

Example

Input	Param	Output
https://example.com?utm_source=google	utm_source	google
/checkout?order_id=ABC%2F123	order_id	ABC/123
https://example.com?foo=bar	missing	undefined
/path/no-query	foo	undefined

Open Source

The Query Param Extractor for GTM Server is developed and maintained by Praba Ponnambalam under the Apache 2.0 license.