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Marketing Problems

How to Test Email Headlines with UTM Parameters

When you send one email with two headlines, or one page with two buttons, a campaign report alone cannot tell you which version worked. The UTM content tag labels each link so you can compare them in your analytics.

Last updated: 2 November 2026

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Step-by-step

  1. Keep the source, medium and campaign the same for both versions, for example newsletter, email and spring-launch.
  2. Open the UTM Generator and enter your destination URL.
  3. In the campaign content box, enter one value per line, such as headline-a and headline-b.
  4. Copy the generated links, one for each content value, and place each in the matching version of your email.
  5. Send both versions to similar, randomly split audiences at the same time.
  6. After enough clicks, compare the content values in your analytics report.

Why the content tag matters

Source, medium and campaign tell you which channel and campaign brought a visit. The content value tells you which link inside that campaign was clicked. Without it, two headlines in the same email look like one campaign in your report.

Reading the results in Google Analytics 4

In Google Analytics 4, the content value is reported as the manual ad content dimension. Add it to a report next to the campaign to see sessions, engagement and conversions for each version.

Keep the test fair

Change one thing at a time, such as the headline, so you know what caused the difference. Split the audience randomly, send both versions together, and wait for enough clicks before deciding. A handful of clicks can look decisive and still be random.

Tagging mistakes to avoid

UTM values are case-sensitive in reports, so headline-A and headline-a are counted separately. Use lowercase with hyphens. Do not add UTM parameters to links inside your own website, because they can start a new session and overwrite the original source. Do not put personal information in a UTM value, since the URL is visible.

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FAQ

Frequently asked questions

What is the UTM content parameter?

It is the utm_content tag. It labels the specific link or creative in a campaign, such as headline-a or footer-link.

How do I test two email headlines?

Keep the campaign tags the same, give each headline its own content value, and compare the results for each value in your analytics.

Where do I see utm_content in Google Analytics 4?

It appears as the manual ad content dimension, which you can add to a report.

How many clicks do I need?

There is no fixed number. Wait until both versions have enough clicks that the difference is larger than normal random variation, and avoid deciding from a handful of clicks.