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What does gad_source mean? Nobody outside Google knows

^Button Solutions·
What does gad_source mean? Nobody outside Google knows
Photo by Daniel Gomez / Unsplash

Google adds gad_source to the landing URL of every ad click, and says the number identifies where the click came from. It does not say which number means what. Two lists circulate, they agree only on 1, and neither comes with data.

What Google says

Google's help pages describe the purpose and stop there. The page on gad_* parameters says gad_source "identifies the source of your ad traffic (e.g., Google Search, Display Network)". It adds that the value cannot be customised, and that all advertisers and campaigns with the same source get the same value.

That tells us the number describes a source, and that it is the same for everyone. It gives two examples of a source and no numbers. The older page on the parameter, the Analytics page and the Search Ads 360 page say the same and no more. The only value any of them shows is gad_source=1, in a test URL.

Two lists that disagree

Search for the values and you find two lists. They agree that 1 is Search and on nothing else.

gad_source List A, by campaign type List B, by placement
1 Google Search Ads Search results, Images tab, Discover
2 Google Display Network YouTube: home, search results, watch pages
3 YouTube Ads not listed
4 Discovery Ads Shopping tab
5 Shopping Ads, including Performance Max Google Display Network
6 not listed Maps tab
7 not listed a guess: ads bought through DV360

The lists put YouTube on different numbers, Display on different numbers, and Shopping on 4 and 5. A dashboard that picks the wrong list tells an advertiser their Display clicks came from YouTube.

Where each list comes from

List A is one Reddit comment. It was posted in r/PPC around February 2025 and has since been removed; a Wayback Machine capture from 2 August 2025 still shows it. The comment is a bare list. It gives no account data, no test and no link. One reply asks whether there is an official document and gets no answer. Another reply says 2 is YouTube.

The articles that repeat List A lead back to it. One links the comment directly and tested only value 1 itself. Another credits "community observations". A third calls it field knowledge and adds 7 as "automated campaign types". None shows a click.

List B is one analyst's testing. It comes from tako-analytics, a Chinese-language analytics blog, first published in February 2024 and updated in October 2024 and January 2025. The author says the values come from manual testing, and labels 7 as a guess. The article does not say how each value was tested or show the clicks. (Nathan's edit: I don't generally like to link chinese pages, but in this case I do agree with claude that the source is slightly more reliable than the deleted r/PPC source I initially based my mapping on.)

So each list has one origin, and neither origin shows evidence. Outside these two, the pages we found either repeat one of them or say the meaning is unknown. A Japanese analytics vendor puts it plainly: only Google knows what the numbers mean.

Campaign type or placement

The lists differ in kind, not only in numbers. List A names campaign types: standard Search campaigns, Shopping campaigns, Performance Max. List B names places an ad was shown: the YouTube watch page, the Shopping tab, the Maps tab.

Google's own wording fits the second reading. It calls the value the source of the traffic and gives "Google Search, Display Network" as examples, which are networks, not campaign types.

Performance Max is where the two readings part. One Performance Max campaign serves on Search, Shopping, YouTube, Display, Discover, Gmail and Maps. If the number followed the campaign type, every click from that campaign would carry the same value. If it follows the placement, one campaign produces several. The tako-analytics author reports a Performance Max shopping ad on the YouTube search page arriving with gad_source=2, which is the placement reading.

That is one report, without the click shown. It makes List B the better guess. It does not make it confirmed.

What we show in the Button dashboard

We had List A in our own code. When we went looking for its source, we found the removed comment and nothing behind it.

The dashboard now names only 1 outright, as Google Search. The other names follow List B, each marked with a star: YouTube*, Google Shopping*, Google Display Network*, Google Maps*, DV360*. A footnote under the table says the starred names are unconfirmed and links the article they come from. Any other number, 3 included, is shown as Google sent it.

We have not yet tested either list against our own traffic. Until we have, a starred name with a footnote is the most we can put on the screen.

Check it in your own account

Google Ads can answer this for any account that runs more than Search. Nils Rooijmans describes the report:

  1. In Google Ads, open Insights and reports, then Landing pages, then Expanded landing pages, in the All campaigns view.
  2. Filter on "Expanded landing page contains gad_source=2".
  3. Segment by Network, or by Click type.
  4. Repeat for 4, 5 and 6.

If the rows for gad_source=2 sit under YouTube, List B is right about 2. If they sit under Display, List A is. An account with Display, YouTube and Shopping traffic settles most of the table in a few minutes.

If you run it, tell us what you see. We will publish the result with our own.

Sources

About this post

Nathan Pankowsky of Button asked the question, recorded the first list, found the archived copy of the removed Reddit comment and decided how the dashboard labels the values. Claude, an AI model made by Anthropic, searched for the sources, compared them and wrote the first draft. Nathan reviewed and edited it.

The quotations from Google's help pages and the summary of the tako-analytics article were read through an automated tool, and the article is in Chinese. Check the linked originals before relying on the exact wording. Nothing here comes from Google beyond what its public help pages say.