Set up a custom experiment

You can create a custom experiment from your original campaign and compare how your experiment performs against your original campaign over time. The experiment shares your original campaign’s traffic (and budget) and lets you test changes to your campaign so that you can make more informed decisions on which tactics give you a better return on investment.

This article explains how to set up a custom experiment. You can also Set up ad variations and Set up video experiments. For more background read about the Experiments page.

Things to note about custom experiments

  • Custom experiments are only available for Search, Display, and Video campaigns. You won’t be able to create an experiment for App or Shopping campaigns.
  • You can schedule up to 5 experiments for a campaign, but you can only run one experiment at a time.
  • It may take some time for your experiment’s ads to complete the review process and to start running, depending on the size of your original campaign. You may want to schedule your experiment to begin in the future to prevent your experiment from beginning before your ads have been reviewed.
  • You can decide what percentage of your original campaign’s budget that you want to allocate to your experiment. For Search campaigns, you can also split your experiment by a cookie-based split or a search-based split. These experiments can help you see which campaign version performs better. You can then decide if you want people to see only your experiment or your original campaign, or show people both randomly.
  • In Display campaigns, we always use cookie splits to ensure that users only ever see the experiment or your original campaign.
  • As your experiment runs, you can monitor its performance.

Keep in mind

If you make changes to your original campaign, those changes won’t be reflected on your experiment. Making changes to either your original campaign or experiment while your experiment is running may make it harder to interpret your results.

If you select the cookie-based split option, and you use audience lists, you should have at least 10,000 users in the list to run an experiment. If you have less users than that, your results may be less accurate.

Instructions

Set up a custom experiment

  1. Sign in to your Google Ads account.
  2. From the page menu on the left, click Experiments near the bottom of the page, then select All experiments.
    Note: If you don't see “Experiments” in the page menu, click More at the bottom of the page menu to expand the available options.
  3. Click the plus button  at the top of the “All Experiments table” and select Custom experiment.
  4. Select Custom experiment(experiment with multiple campaign optimizations for any campaign) and click Continue.
  5. In the “Set up the experiment” section, enter the name of your experiment and description (optional). Your experiment shouldn’t share the same name as your campaigns and other experiments.
    1. Choose the original campaigns you want to test in your experiment. We’ll display the campaigns you selected and automatically create the experiments.
    2. Label your test campaigns with a suffix to distinguish it from the original campaigns. We’ll append the suffix to all of your test campaigns. For example, “Campaign 2 (Holiday_test)”.
    3. Click Continue to finish the setup of the experiment. The next page will let you make changes and schedule the experiment.
  6. To make changes to the experiment, select up to 2 goals to measure your success metric. For example, select “Clicks” and “Increase” for the first goal.
    Note: These success metrics will be emphasized in the campaign report, however you will still see all of the other metrics as they are normally reported.
    1. In the “Experiment split” section, select the traffic and budget you want to split your experiment by. We recommend using 50% to provide the best comparison between the original and experiment campaigns.
    2. Select the “Advanced” options you want to use in the experiment:
      • Cookie-based (recommended) randomly assigns users to either your experiment or original campaign and ensures that a given user only sees either the original or the experiment.
      • Search-based randomly assigns users to either your experiment or original campaign every time a search occurs. If a user runs multiple searches, the same user could see both the experiment and your original campaign. This option may get statistically significant results faster than a cookie-based split.
  7. In the “Schedule the experiment” section, select the start and duration in “Experiment dates”. The program will determine the end date.
  8. Click Save to finish creating the experiments. Your experiment is now completed and ready to run.
Note: After you have set up and scheduled your custom experiment, you can monitor your custom experiments.

Fix issues creating an experiment

In some instances, you may encounter an error when trying to create an experiment. Here are a few reasons why this could happen, along with steps you can take to fix these errors.

What you can do when you're ready to end your experiment

If you’re happy with experiment results, you can apply your experiment to the original campaign or convert your experiment into a new campaign.

  • If you apply your experiment to your original campaign, the changes you were testing in your experiment will be applied to your original campaign.
  • After converting your experiment into a new campaign, be sure to check the resulting campaign to ensure all changes were properly applied.

In both instances, your experiment’s performance data will be preserved. Learn more about how to apply your experiment

If you prefer to simply end your experiment, you can do that by changing the end date of your experiment so it stops running at the close of the day. You can also click Edit in the upper-right corner of the page and select End now. Learn more about making changes to your experiments

Note: Creatives in campaigns that are under the “setup” or “creating” status will not go through the review process. As a result, the creative status will stay “Under Review” until the draft is applied to the original campaign.

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