Introduction: Understanding GTM vs Google Analytics for UK Businesses
If you manage an ecommerce or lead generation website in the UK, you've probably heard about "GTM vs Google Analytics." These two Google tools are essential but serve different purposes. This guide explains the difference clearly, from GA3 to GA4, the role of a GTM ID, and why GTM is widely used. After reading, you’ll know how to set up and use both tools to track the right data and improve marketing decisions.
What is Google Tag Manager and why is it used?
Google Tag Manager, or GTM, lets you add and manage small pieces of code called "tags" on your website without modifying the site’s code directly. Tags send data to other services like Google Analytics or Facebook Ads. Without GTM, each tag needs manual code updates, which can be slow and error-prone.
GTM provides a web interface where you can create, update, and disable tags across your site quickly. This reduces mistakes and speeds up adding new marketing or tracking codes, which is why many businesses prefer it.
Businesses use GTM because:
- It centralises tag management in one place.
- It removes the need for developer help to add marketing and analytics tags.
- It improves data accuracy by controlling when and how tags fire.
- It supports adding tags for multiple platforms like Google Ads, Facebook, and LinkedIn.
GTM is free and works with most websites and content management systems (CMS).
What is Google Analytics and how does it work?
Google Analytics (GA) is the platform that collects and reports information about your website visitors. It shows how people find your site, what pages they visit, how long they stay, and how many complete goals like purchases or contact forms.
GA uses "tracking code" (a type of tag) on your website to gather this data. This code sends information back to your Google Analytics property where it’s processed into reports.
GA4, the latest version of Google Analytics, is designed to handle modern privacy challenges and tracks users via "events." This means it focuses on specific actions visitors take, not just page views or sessions.
GA itself doesn’t add or manage tags. That’s usually handled by GTM or through manual site code.
What is the difference between GA3 and GA4?
GA3 stands for Universal Analytics, the previous version of Google Analytics. It groups user interactions into "sessions"—time periods during which a visitor interacts with your site.
GA4 changed the model to event-based tracking. Every interaction (page view, click, form submission) is an event, giving you more detailed insights.
Key differences include:
- GA4 tracks more user actions automatically, such as scrolls and video engagement.
- GA4 is built to respect user privacy and comply with laws like the UK GDPR.
- GA4 improves integration with Google Ads for better marketing attribution.
- GA3 stopped processing new data in July 2023, so all sites should migrate to GA4.
While GA4 offers more flexibility, it requires setting up events and conversions carefully to track your goals properly.
GA4 vs GTM: What is the relationship?
GA4 and GTM don’t compete; they work together.
GA4 collects and reports data about your site visitors. GTM is the tool you use to add the GA4 tracking code (called a tag) to your website without editing the site's files.
Using GTM, you can:
- Deploy the GA4 configuration tag that sends visitor data to GA4.
- Add tags for other tools like Facebook Pixel or Google Ads conversion tracking.
- Control when and where tags fire based on user behaviour or page types.
Without GTM, you'd add GA4 code manually, which can be tricky if you have several tracking needs.
What is a Google Tag Manager ID?
When you create a GTM account and container (the workspace for your website’s tags), Google assigns a unique Google Tag Manager ID.
It looks like GTM-XXXXXX.
You add this ID snippet to your website's code or through your CMS settings (e.g., Shopify or WordPress). This connects your site to your GTM container, allowing the GTM interface to manage your website’s tags remotely.
This single ID is crucial: without it, GTM can’t operate on your site.
Step-by-step: Setting up GTM with GA4 on your UK ecommerce or lead generation site
- Create a GTM account and container: Go to tagmanager.google.com, set up your account and container for your website.
- Install GTM on your site: Add the GTM ID snippet code to your website’s header and body sections manually or use your CMS’s plugin or theme settings.
- Create a GA4 property: In analytics.google.com, set up a GA4 property for your site.
- Find your GA4 measurement ID: It starts with G- and looks like G-XXXXXXXX.
- Add a GA4 configuration tag in GTM: In GTM, create a new tag, choose "Google Analytics: GA4 Configuration," and enter your GA4 measurement ID.
- Set the trigger to "All Pages": This ensures the tag fires on every page.
- Publish the GTM container: Click Submit to make your changes live.
- Test the setup: Use GTM Preview mode and check GA4 real-time reports to confirm tracking works.
Checklist for GTM vs Google Analytics setup
- [ ] GTM container set up with correct GTM ID on your website
- [ ] GA4 property created and measurement ID noted
- [ ] GA4 configuration tag added to GTM
- [ ] Appropriate triggers set (All Pages minimum)
- [ ] Custom events and conversions created as needed for your goals
- [ ] Other marketing tags added via GTM (Facebook, Google Ads, LinkedIn)
- [ ] Regular testing of tags using GTM preview and GA4 real-time reports
- [ ] Compliance with UK GDPR cookie consent and data policies
Common mistakes with GTM and Google Analytics
- Installing GA tags both directly on the site and via GTM, which leads to double counting visits or conversions.
- Forgetting to publish GTM changes after adding tags or triggers.
- Not switching from GA3 (Universal Analytics) to GA4, causing data loss.
- Ignoring cookie consent laws in the UK, risking legal issues.
- Skipping testing tags before going live, leading to missed or inaccurate data.
- Confusing GTM and GA4 roles and trying to use one in place of the other.
Worked UK example: Using GTM and GA4 for a local gift shop’s website
Lisa owns a gift shop in Manchester with an online store. She wants to track sales and newsletter sign-ups clearly.
- Lisa creates a GTM account and installs the GTM container code on her Shopify site using her GTM ID.
- She sets up a GA4 property and notes her measurement ID.
- In GTM, Lisa adds a GA4 configuration tag with her measurement ID set to fire on all pages.
- She creates GA4 event tags for purchase completion and newsletter sign-up, triggered by thank you pages.
Results Lisa sees:
- Her GA4 dashboard shows accurate transaction numbers aligned with Shopify sales.
- She identifies which digital ads bring visitors who convert.
- Marketing decisions are based on solid data, improving her ad spend.
What it means for you
Understanding the roles of GTM versus Google Analytics helps you track your website’s performance properly. GTM is your tag manager, simplifying deployment and updates. GA4 is your data platform, letting you analyse visitor behaviour and conversions.
For UK businesses, moving fully to GA4 and managing tags via GTM improves accuracy and compliance. It also helps you respond quickly to new marketing needs without expensive developer time.
Regular testing and configuring the right events in GA4 ensures you measure what matters. Avoid common setup errors and keep up with data privacy requirements.
If you’d like guidance or expert help, my Google Ads, Meta Ads, SEO and web development services cover setup and ongoing support. Also, try these free tools: my site speed checker and revenue loss calculator or ROAS calculator.
What to do next
Create your GTM account and GA4 property this week if you haven’t already. Add GTM ID to your site and deploy the GA4 configuration tag via GTM. Test your setup using GTM preview and GA4 real-time.
If you prefer help, get in touch with me. Alternatively, explore more free tools at https://www.anthonymcgrath.co/tools/.
