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Google Tag Manager

Custom GTM Template Development

Purpose-built GTM custom templates for your specific tags, pixels, or tracking logic. Sandboxed, reusable, and deployable without custom HTML tags.

GTM Implementation

Purpose-built GTM custom templates for your specific tags or tracking logic, sandboxed and configurable without custom HTML.

Best for

Teams managing vendor tags without official GTM templates, or complex firing logic that currently requires multiple custom HTML tags to maintain.

  • 8-20 hours, up to 2 templates per engagement
  • Includes a configuration UI for non-developers
  • Template exported for backup and portability
  • Standard GTM Sandbox API required

Overview

How to know if you need Custom GTM Template Development

  • You are managing a vendor tag via a custom HTML tag because no official GTM template exists.
  • When the vendor updates their snippet, someone has to find the tag in GTM and update the code manually.
  • Your tracking logic requires multiple custom HTML tags that are difficult to maintain and document.
  • You want non-developers to be able to configure tag settings without touching JavaScript.
  • You want to reuse the same tag implementation across multiple GTM containers without copying custom HTML.

What Custom GTM Template Development covers

  • A sandboxed GTM custom template built against your vendor's specification or your internal tracking library.
  • A configuration UI so non-developers can manage tag settings without editing code.
  • Implementation within GTM's Sandbox API security model, with permissions declared explicitly.
  • Testing against your container and validation with GTM's built-in lint checks.
  • Template exported from your workspace for backup and reuse across other containers.

Custom GTM Template Development outcomes

  • A template in your GTM workspace your team controls and can update without touching raw JavaScript.
  • Non-developer team members can configure tag settings through the template UI.
  • The template is portable: exported and reusable across other containers without rebuilding from scratch.

Custom GTM Template Development scope and hours

  • 8-20 hours depending on template complexity, up to 2 templates per engagement.
  • Vendor documentation or a specification for your internal library is required before work starts.
  • GTM's Sandbox API imposes security restrictions. Some vendor features may require review for compatibility.
  • Scope confirmed after reviewing the vendor spec and your specific requirements.

What makes our Custom GTM Template Development different

  • The template works within GTM's security model, not around it. No unsafe eval, no undeclared permissions.
  • The configuration UI is designed for the people who will actually use it, not just for the developer who built it.
  • You receive documentation covering every field in the template UI and the expected output.
  • The template is tested against your actual container, not just a demo environment.
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Free

Free Generic Tracking

A high-level review of your overall tracking setup: event coverage, obvious configuration errors, attribution quality, and the highest-impact quick wins across your analytics and ad platforms.

Tracking Setup Quick Wins Analytics Ad Platforms
Free

Free GTM Container

A surface-level review of your Google Tag Manager container: tag count, obvious duplicates, missing consent triggers, broken references, and the highest-impact issues. Delivered as a written summary.

GTM Tag Inventory Consent Triggers Duplicates
Free

Free Consent Mode

A basic review of your Google Consent Mode v2 implementation: whether it is configured, which mode is active (Basic or Advanced), and whether consent states appear to be respected by your key tags.

Consent Mode v2 CMP GDPR Tag Firing
Free

Free Website Performance

A Lighthouse-based snapshot of your Core Web Vitals on key page templates, with a basic assessment of how your tag stack is affecting page speed. Delivered as a written summary with the top tag-related performance issues identified.

Core Web Vitals Lighthouse Tag Load Impact Page Speed
Free

Free GA4 Analytics

A spot-check of your GA4 property: event volume, obvious tracking gaps, and a comparison of your reported conversion numbers against expected behaviour. Delivered as a written summary with the top issues identified.

GA4 Event Coverage Conversion Gaps Data Quality
Our approach

How we deliver Custom GTM Template Development.

A structured process built around your stack, your team, and your data.

01

Specification review

We review your tag requirements, vendor documentation, and the specific parameters your team needs to configure in the template UI.

02

Sandbox API mapping

We identify which GTM Sandbox API methods are appropriate for your tag's needs within GTM's security model.

03

Template development

The template is built with a configuration UI, tested against your container, and validated with GTM's built-in lint checks.

04

Documentation

We write configuration documentation covering every field in the template UI and the expected output.

05

Handover

The template is deployed to your workspace with a test container demonstrating it working end-to-end.

Frequently Asked Questions

Can any vendor tag be turned into a GTM custom template?
Most can, but GTM's Sandbox API has restrictions. Some vendor tags rely on browser APIs or third-party libraries that are not accessible from within a sandboxed template. We review the vendor spec before committing to scope.
What is the GTM Sandbox API?
It is the set of methods available to code running inside a GTM custom template. It provides access to common browser and tracking functions within a security boundary, replacing direct access to the global window object.
Will the template work across multiple GTM containers?
Yes. The template is exported from your workspace and can be imported into any other container. It does not need to be rebuilt for each container.
Can non-developers use the template once it is built?
Yes. The configuration UI is designed for this purpose. Tag settings like IDs, event names, and parameters are exposed as form fields your team can update without editing code.

Pairs well with

01

Google Tag Manager Audit

Full programmatic export analysis of your GTM container. Every tag, trigger, and variable reviewed: naming conventions, performance impact per tag, consent compliance, broken references, unused elements, and trigger overlaps. Delivered as a prioritised findings report with specific remediation steps.

02

Custom Data Layer Design

Data layer architecture and specification for scalable, platform-agnostic tracking with developer-ready documentation.

03

GTM Training & Documentation Package

Structured GTM training for your team: container fundamentals, your specific implementation, custom HTML and JavaScript basics, and a documentation package tailored to your setup.

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