ChatGPT utm_source parameter

Definition: The ChatGPT utm_source parameter is the URL label utm_source=chatgpt.com, which declares ChatGPT as a traffic source. Analytics software can use this label to attribute visits arriving through tagged links.

Key facts

• As of October 2026, OpenAI's API reference includes utm_source=chatgpt.com in example citation URLs.
• As of October 2026, Google's campaign URL documentation defines utm_source as the referrer label and explains that clicked referral links send their parameters to Analytics.
• Google's manual tagging documentation maps utm_source to manual source dimensions, including Session manual source.
• Google's acquisition report comparison distinguishes reports about new users from reports about new sessions, meaning visits.

What does the parameter contain?

A URL parameter is a name and value attached to a web address. In this case, the name is utm_source and the value is chatgpt.com:

utm_source=chatgpt.com

OpenAI's response example places this exact label inside the URL field of a url_citation annotation, a reference attached to an answer. This establishes a concrete documented use of the label in a source link.

Google's URL construction instructions put a question mark before parameters, an equals sign between each name and value, and an ampersand between pairs. Parameter values are case sensitive. The exact spelling matters when grouping visits under a source value.

How should the label be interpreted?

Google's traffic-source documentation defines source as where traffic originates and medium as how users arrive. The utm_source field supplies the source value; utm_medium is a separate field. The word “referral” in an account of a visit therefore needs to be distinguished from the medium value actually recorded.

The same documentation allows manually supplied parameter values. Consequently, a tagged URL provides a declared source label; confirming a particular answer's citation requires checking the answer and its link. The tag alone cannot establish how many answers display a page.

Where can a website check it?

Google's campaign reporting instructions place Session source and Session source/medium in Acquisition > Traffic acquisition. These fields provide a starting point for examining visits attributed to chatgpt.com.

The same instructions state that UTM parameters are omitted from Landing page + query string and Page path + query string. Page location contains that UTM information. This distinction matters when checking whether a collected page address retains the tag.

Google's report comparison assigns Session source to session analysis and First user source to user acquisition. A report should name the dimension used alongside its totals so that the totals have a clear interpretation.

Related terms

• AI referral traffic
• UTM parameters
• GA4 traffic acquisition
• AI citation

FAQ

Does the source value also specify a medium?

Google's parameter mapping assigns source and medium to separate parameters. Check the recorded medium alongside the source before interpreting a report row.

Can I inspect the tag in a landing-page report?

Google's URL builder documentation says UTM information is populated in Page location. Use that dimension when inspecting the collected URL for the tag.

Should I use First user source to count referral sessions?

Google's acquisition comparison distinguishes user scope from session scope. Use Session source when examining session acquisition and state that scope in the report.

Sources

1. OpenAI, "Create a model response", accessed 17 October 2026
2. Google, "URL builders: Collect campaign data with custom URLs", accessed 17 October 2026
3. Google, "Traffic-source dimensions, manual tagging, and auto-tagging", accessed 17 October 2026
4. Google, "User acquisition report vs. Traffic acquisition report", accessed 17 October 2026

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