Most tracking breaks quietly. Nobody gets an error message. A conversion count drifts, a remarketing tag fires twice, or a report stops matching the backend, and weeks pass before anyone asks why.
In October, Google shipped two changes to Google Tag Manager (GTM) that can cause exactly this kind of quiet drift. Neither is dramatic on its own. Both touch how GTM starts up and which events it sees, and that is the part of a setup most teams have not looked at in years.
This article explains what changed, who is affected, and five checks your team can run this week, before the next campaign launch or reporting cycle.
What changed in October
According to the Google Tag Manager release notes, two updates landed within a week of each other.
October 8: config commands now show up as events
Google says that all GTM container snippets (gtm.js) now initialize on container load, whether or not the page runs any gtag(‘config’) commands. Those config commands now appear in the dataLayer as a new event called gtag.config.
Google’s own note warns that if your container uses wildcard custom event triggers, tags attached to them may now fire. In plain terms: a trigger built to catch “every custom event” now catches one more.
October 12: containers can talk to Google products directly
Google also released container optimization. An optimized container can send data straight to Google destinations, such as Google Analytics (GA) and Google Ads, without loading a separate gtag.js script. Your Google tag settings move into the container, under a new Settings tab.
This one is optional. Google’s announcement of the Google tag and GTM updates (August 20, 2026) says no changes will be made automatically. You choose when to optimize.
Who should pay attention
Three groups need to act, in this order of urgency.
- Sites with a mixed setup. Google calls this an unsupported implementation: a GTM snippet on the page, plus standalone gtag(‘config’) commands for Google tag identifiers (IDs) starting with G- (Google Analytics), AW- (Google Ads) or DC- (Floodlight), without the gtag.js loader. Google’s setup guide for gtag.js says these sites “may experience unexpected changes to their tag behavior”. Google also says accounts with these containers received an email notification.
- Containers with catch-all triggers. If any trigger uses a regular expression (regex) such as .* to match all custom events, it can now pick up gtag.config. This applies even to correct setups, because the standard gtag.js snippet itself contains a config command.
- Teams planning to optimize their container. The upgrade is useful, but it consolidates settings, and some choices are not easy to reverse.
If you work with an agency or a development partner, do not assume someone else saw the email. In our experience, notices like this land in an inbox that belongs to a person who left two years ago.
5 checks to run this week
1. Search the email inbox tied to your Google accounts
Look for a Google notice about an unsupported Google tag implementation. If one arrived, treat the container it names as your first priority. If none arrived, still run the checks below. An absent email is not proof of a clean setup.
2. Confirm how your Google tag actually loads
Google’s guide gives two ways to check:
- Tag Assistant: add your domain and confirm your tag ID appears under “Google tags found” with a green or blue status icon.
- Chrome DevTools: in the Network tab, check that requests go to googletagmanager.com/gtag/js rather than /gtm.js for your Google Analytics or Google Ads tag.
If you find the mixed pattern, Google’s fix is clear. Either move to the full gtag.js snippet on every page and remove the standalone config lines, or keep GTM and deploy the Google tag inside the container.
3. Audit every wildcard custom event trigger
In GTM, open Triggers and filter for Custom Event triggers with “use regex matching” switched on. For each one that matches broadly:
- List the tags it fires. Pay most attention to conversion pixels, remarketing tags and anything that sends data to a third party.
- Add a condition that excludes the gtag.config event, or narrow the regex to the events you actually need.
- Test in Preview mode and watch whether gtag.config appears in the event list and fires anything.
4. Compare this month’s counts against last month
Pull the conversion and event counts that matter most, by day, from October 1 onwards. A sudden step up after October 8 with no campaign change behind it is worth a closer look. Check advertising platforms too, not only Google Analytics. An extra pixel firing inflates conversions in the platform that bids on them.
5. Re-test consent before anything else
Because containers no longer wait for config commands, the order in which things load can shift. Open Preview mode with consent declined and confirm your consent management platform (CMP) sets its defaults before any marketing tag fires. This is our recommendation, not a step Google lists, but it is the check we would not skip on any site that serves users in privacy-regulated markets.
Should you optimize your container now?
Optimization removes the extra gtag.js load and puts Google tag settings under GTM’s version control, which is a real improvement for most teams. Before you click “Review details” on the banner, note three caveats from Google’s documentation:
- If your Google tags use different settings, you must choose one set to keep. The others are not carried over.
- Destination permissions are not versioned, so rolling back a container version will not restore them.
- You can undo changes in the workspace before publishing. After publishing, you roll back to a prior version.
Our advice: fix wildcard triggers and any mixed setup first. Optimize second, in a workspace, with a written note of the settings you are replacing.
Final thoughts
These are small platform changes with a wide blast radius, because GTM sits in front of almost every marketing tag on a site. One focused hour this week, covering the inbox, the snippet, the triggers, the counts and consent, is enough to know whether your data changed on October 8 or not. If it did, you will want to find out before someone else does.
Sources
- Google, Tag Manager Help: Release notes (October 8 and October 12, 2026 entries)
- Google, Tag Manager Help: Set up your Google tag installation correctly for gtag.js (accessed October 25, 2026)
- Google, Tag Manager Help: Optimize your Google Tag Manager container (accessed October 25, 2026)
- Google, Tag Manager Help: Updates to Google tag and Google Tag Manager (August 20, 2026)
- Google, Tag Manager Help: Custom event triggers (accessed October 25, 2026)
How Gmetrics can help
Our Analytics & Insights team audits GTM containers, Google Analytics setups and tag firing logic, and we can run this checklist with your team. Contact us to book a review of your setup before your next campaign or reporting cycle.
