Practical guides

A/B testing with Google Tag Manager

GTM Custom HTML, All Pages trigger, preview and Testvoy tracking verifier flow.

Last updated: May 22, 20268-14 minBeginner to intermediate
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Publishing Testvoy with GTM

Google Tag Manager setup is practical for teams that want to publish the SDK across public pages without entering the development queue. Add the Testvoy snippet to a Custom HTML tag, choose the All Pages trigger, verify in Preview mode and then publish.

  1. 01

    Create a New Tag in GTM

  2. 02

    Choose Custom HTML

  3. 03

    Paste the Testvoy SDK snippet

  4. 04

    Use All Pages trigger

  5. 05

    Verify SDK loaded and recent events in Preview mode

  6. 06

    Publish when duplicate loading is clear

JavaScript SDK snippet
<head>
  <title>Store Name | Online Shopping</title>
  <script
    async
    src="https://cdn.testvoy.com/sdk/v1/testvoy.min.js"
    data-project-key="PROJECT_KEY_HERE">
  </script>
  <meta name="description" content="Discover products and buy with confidence." />
</head>
GTM preview verification
GTMPreviewVerifier
Tag fired, SDK loaded, accepted event and dropped event signals are checked together.

Common GTM mistakes

Most GTM setup issues come from trigger scope, consent mode, duplicate SDK loading or production/staging container mixups. The Testvoy verifier helps catch these early.

Trigger fires only on one page

Consent mode prevents the tag from firing

Theme code and GTM load the same snippet twice

It works in preview but was not published

Project key belongs to the wrong environment

Implementation example: Custom HTML tag in GTM

If you use GTM, place the snippet in a Custom HTML tag instead of directly editing site code. Use All Pages as the trigger, then verify in Preview mode that the tag fires and Testvoy verifier shows SDK loaded.

  1. 01

    Go to GTM > Tags > New

  2. 02

    Choose Tag type: Custom HTML

  3. 03

    Paste the script below

  4. 04

    Choose Trigger: All Pages

  5. 05

    Open the site in Preview mode

  6. 06

    Check Tag fired and Testvoy accepted event signals

  7. 07

    If clean, Submit > Publish

GTM Custom HTML content
<script
  async
  src="https://cdn.testvoy.com/sdk/v1/testvoy.min.js"
  data-project-key="PROJECT_KEY_HERE">
</script>

Practical scenario

A growth team changes CTA copy on the pricing page, connects signup_started and signup_completed goals, then reads Google Ads and returning visitor segments separately. If the result is promising, they share a report link with the client or leadership.

Common mistakes

Most mistakes come from wrong project keys, overly broad selectors, missing goals, staging/prod mixups, early decisions on small samples or skipping mobile QA.

Naming an experiment 'test'

Launching without a goal

Deciding on total CVR only

Sending screenshots instead of shareable reports

Related pages

InstallationGoogle Tag Manager setup

Publish the Testvoy SDK on all pages using a GTM Custom HTML tag and verify with preview.

Frequently asked questions

Who is A/B testing with Google Tag Manager for?

Marketing, growth, product and developer teams can use the same guide at different depths.

Do I need a developer?

Not for basic visual changes and report reading; SDK, custom events, custom JS or enterprise security benefit from technical support.

How do I know it worked?

Verifier, recent events, preview, QA checklist and report warnings show setup and experiment health.

What is the common mistake?

Wrong project keys, missing goals, fragile selectors, early decisions on small samples and skipped mobile QA are common.

Docs

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