There are many different metrics that can be used to measure the performance of a digital marketing campaign. Some common key performance indicators (KPIs) include:

1. Traffic: The number of visitors to a website or landing page.

2. Conversion rate: The percentage of website visitors who take a desired action, such as making a purchase or filling out a form.

3. Bounce rate: The percentage of website visitors who leave a website after only viewing one page.

4. Average time on site: The average amount of time a visitor spends on a website.

5. Cost per conversion: The amount of money spent on a marketing campaign divided by the number of conversions.

6. Return on investment (ROI): The amount of revenue generated by a marketing campaign divided by the cost of the campaign.

7. Cost per click (CPC): The amount of money spent on a marketing campaign divided by the number of clicks.

8. Click-through rate (CTR): The percentage of people who click on a link out of the total number of people who see it.

9. Engagement rate: The number of people who engage with a piece of content on social media.

These are general purpose examples, specific business could have their own specific metrics.