# GA4 for AI Search: A Monthly Measurement Routine

> A one-hour monthly GA4 routine for AI search: AI Assistant traffic, landing pages, key events, Search Console and a BigQuery check.

Source: https://mentionx.ai/learn/ga4/ga4-ai-search-monthly-measurement-routine  
Author: Dipuck Jones, founder of MentionX  
Updated: 4 November 2026  
Level: Practitioner

**Once a month, spend about an hour on five checks: AI Assistant sessions and sources, the landing pages they reach, the key events they drive, Search Console for organic and branded demand, and a sanity check of tagging and regex.** Write the results in the same table every month so the trend, not one number, is what you report.

> **Key takeaways**
>
> - Use the default channel group's AI Assistant channel as the headline, and your custom AI channel as the fuller view.
> - Always look at landing pages and key events, not just sessions.
> - Google counts AI Overviews and AI Mode as Organic Search, so GA4 alone can't show them.
> - Search Console data lags about 48 hours, so run the routine a few days into the month.
> - Review your regex and the session sources it misses every month.

*Checked 4 November 2026 (CET) against Google Analytics Help and Google developer documentation. GA4 menus and limits change, so confirm in your own property. "Our view" marks MentionX opinion. Ledgerline is a fictional company used for illustration.*

## Before the first run

Set these up once. Each links to the lesson that covers it.

| Prerequisite | Lesson |
|---|---|
| Key events marked (demo, trial, contact) | [Key events: what replaced conversions](https://mentionx.ai/learn/ga4/ga4-key-events-setup) |
| Data retention at 14 months | [GA4 property setup checklist for marketers](https://mentionx.ai/learn/ga4/ga4-property-setup-checklist) |
| Custom channel group with an AI channel above Referral | [AI referral traffic: the AI Assistant channel and a custom regex](https://mentionx.ai/learn/ga4/ga4-ai-assistant-channel-regex) |
| Search Console linked | [Linking Search Console and Google Ads](https://mentionx.ai/learn/ga4/ga4-search-console-google-ads-links) |
| BigQuery export on (optional) | [BigQuery export on the free tier](https://mentionx.ai/learn/ga4/ga4-bigquery-export-free-tier) |

## The monthly checks

**1. AI traffic headline (10 minutes).** Open **Reports → Acquisition → Traffic acquisition**, set last month vs the previous month, and read the **AI Assistant** row of the default channel group. Then switch the primary dimension to your custom channel group and add **Session source** as a secondary dimension.

**2. Sources you aren't catching (10 minutes).** Still in Traffic acquisition, set the dimension to **Session source / medium** and search for `ai`, `gpt`, `chat`, `copilot` and `assistant`. Any assistant-like source sitting in Referral or Unassigned is a candidate for your regex. Edit it in Admin → Data display → Channel groups. Custom groups apply to past data, so the fix is retroactive.

**3. Landing pages (15 minutes).** Use a free-form exploration (see [Free-form explorations and segments](https://mentionx.ai/learn/ga4/ga4-free-form-explorations-segments)):

| Setting | Value |
|---|---|
| Rows | Landing page + query string |
| Columns | Your custom channel group |
| Values | Sessions, Engaged sessions, Key events |
| Filter | Custom channel group exactly matches your AI channel name |

Save it once and reuse it. The short list it returns is the set of pages AI users actually reach, so keep them accurate and current.

**4. Outcomes (10 minutes).** In the same exploration, add **Event name** as a column filtered to your key events. Compare the AI channel's key event rate with Organic Search. With small volumes, report counts and rates together and avoid claiming a precise difference.

**5. Search Console and demand (15 minutes).** In the Search Console report collection (lesson 15) or Search Console itself, check branded query clicks and impressions month over month. Rising branded demand alongside flat AI referrals is a common pattern when people read an AI answer and then search for you.

## Optional: the BigQuery check

If export is on, this query counts sessions by assistant-like source for a month. Replace the project and dataset.

```sql
SELECT
  collected_traffic_source.manual_source AS utm_source,
  REGEXP_EXTRACT((SELECT value.string_value FROM UNNEST(event_params) WHERE key = 'page_referrer'), r'^https?://([^/]+)') AS referrer_host,
  COUNT(*) AS session_starts
FROM `your-project.analytics_123456789.events_*`
WHERE _TABLE_SUFFIX BETWEEN '20261001' AND '20261031'
  AND event_name = 'session_start'
GROUP BY 1, 2
HAVING REGEXP_CONTAINS(LOWER(CONCAT(IFNULL(utm_source, ''), ' ', IFNULL(referrer_host, ''))), r'chatgpt|openai|perplexity|gemini|copilot|claude|deepseek|grok')
ORDER BY session_starts DESC;
```

Referrer hosts here are the raw truth your regex should match. Remember that sandbox tables expire after 60 days, so run it before last month's tables disappear.

## The monthly table

Copy this into a sheet and add one row per month.

| Month | AI Assistant sessions (default) | Custom AI channel sessions | Top 3 AI landing pages | AI key events | Branded clicks (Search Console) | Regex changes | Notes |
|---|---|---|---|---|---|---|---|
| | | | | | | | |

*Illustrative example.* Ledgerline, a fictional finance software company, runs this on the 4th of each month. In one review it finds a new assistant source in Referral, adds it to the regex, and notes the change in the table so the jump in the custom channel isn't misread as growth.

> **Pro move:** add a "regex changes" column and never skip it. A custom channel's trend is only meaningful if you know when its definition changed.

## What GA4 can't tell you

GA4 measures visits. It can't show how often an assistant mentions or recommends you without a click, or what it says. Pair this routine with prompt tracking, and with "How did you hear about us?" on forms, as covered in [self-reported attribution](https://mentionx.ai/learn/measurement/self-reported-attribution-adding-chatgpt-forms) and [AI visibility KPIs for marketing teams](https://mentionx.ai/learn/measurement/ai-visibility-kpis-marketing-teams). For assistant-specific tracking see [measuring brand visibility in Claude](https://mentionx.ai/learn/claude/measure-brand-visibility-claude) and [Tracking ChatGPT referral traffic and mentions](https://mentionx.ai/learn/chatgpt/track-chatgpt-referral-traffic-mentions).

*Our view:* report AI referrals as one leading indicator among several. Treating them as the total effect of AI search undersells it.

You have finished the track. Return to the [GA4 for Marketers track](https://mentionx.ai/learn/ga4/ga4-for-marketers).

## Common questions

**How often should I review AI traffic in GA4?** Monthly is enough for most teams. Volumes are usually small, so weekly numbers swing too much to act on.

**Why does my AI Assistant number differ from my custom channel?** They use different rules. The default AI Assistant channel uses Google's own list of assistants; your custom group uses your regex. Report one consistently and note which.

**Does GA4 show traffic from AI Overviews?** Not separately. Google counts AI Overviews and AI Mode visits as Organic Search, so use Search Console and your own prompt tracking alongside GA4.

## Sources

- Google Analytics Help, [Default channel group](https://support.google.com/analytics/answer/9756891)
- Google Analytics Help, [Custom channel groups](https://support.google.com/analytics/answer/13051316)
- Google Analytics Help, [Get started with Explorations](https://support.google.com/analytics/answer/7579450)
- Google Analytics Help, [Connect Search Console to Google Analytics](https://support.google.com/analytics/answer/10737381)
- Google Analytics Help, [BigQuery Export schema](https://support.google.com/analytics/answer/7029846)
- Google Cloud, [BigQuery sandbox](https://cloud.google.com/bigquery/docs/sandbox)
- All accessed 4 Nov 2026.

## Frequently asked questions

### How often should I review AI traffic in GA4?

Monthly is enough for most teams. Volumes are usually small, so weekly numbers swing too much to act on.

### Why does my AI Assistant number differ from my custom channel?

They use different rules. The default AI Assistant channel uses Google's own list of assistants; your custom group uses your regex. Report one consistently and note which.

### Does GA4 show traffic from AI Overviews?

Not separately. Google counts AI Overviews and AI Mode visits as Organic Search, so use Search Console and your own prompt tracking alongside GA4.

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Written and reviewed by Dipuck Jones for MentionX Learn. The HTML version of this page: https://mentionx.ai/learn/ga4/ga4-ai-search-monthly-measurement-routine