Google Optimize will no longer be available after September 30, 2023. Your experiments and personalizations can continue to run until that date. Learn more


A guide to one of the key building blocks of Optimize.

An Optimize container holds all of the configurations for your experiences. An Optimize account must have at least one container and you should set up one container for each Analytics property with the domain name as the container name field.

A container snippet is a small piece of JavaScript code that must be added to any web page(s) being tested.

A container ID is an alphanumeric string beginning with "OPT-" or "GTM-" that uniquely identifies a container (e.g. "OPT-A1B2CD"). The container ID can be found in the container settings in Optimize.

Beginning in 2020, all Optimize IDs begin with "OPT-". This will help Google Tag Manager (GTM) users differentiate between GTM and Optimize containers and coincides with the launch of the optimize.js snippet.

Container best practices

  • Set up containers based on your organizational structure.
  • If you need to run experiences on one domain without affecting other domains, use a different container for each domain.
  • If your user journey spans multiple domains (e.g. an ecommerce site with a separate shopping cart site), create a single container for all of the domains involved. Note: Cross-domain redirect experiments aren't supported at this time.
  • Experiences cannot be run and measured across different top level domains. You can implement the same container on multiple domains, but be sure to leverage targeting rules to determine a unique domain that should be targeted by a given experiment. Experiments can be run and measured across subdomains, as long as all subdomains are tracked in the same Analytics property. You should implement the same container on all subdomains.

Optimize container types

  • Stored containers include all draft, scheduled, running, and ended experiences created in a container and contribute to the overall "stored container" size. To reduce the size of a stored container, archive some ended experiments.
  • Served containers only include the running experiences and the data is compressed. To reduce the size of a served container, end some of its experiences.

Container size management

Each Optimize container is allocated capacity to run your experiences. Only actively running experiences are included in this capacity so it will naturally fluctuate as experiences start and end. As usage reaches certain thresholds, you may see capacity information appear in a banner at the top of your container page.

A container limit banner will appear when a served container hits the following thresholds:

  • 50% of capacity
  • 70% of capacity
  • 90% of capacity

When a served container reaches 100% of its capacity, you won't be able to make additional changes.

Note: Container capacity is only updated when an experience is manually started or ended.

Reduce container size

To resolve capacity issues, try the following:

  • Start new experiences with less changes and/or variants.
  • End running experiences before starting new ones.
  • Use different containers across different parts of your site. When combined with container-level permissions, multiple smaller containers allow you to control access to who test different parts of your site.
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