What does a 28 day Free Trial mean?

The 28-day free trial is for Magento & custom platform.

No credit card required to start our free trial. Just signup, get API keys, and proceed. 

Before your free trial, you will automatically be assigned a plan based on your usage pattern (number of searches/pageviews/impressions/SKU count).   

You can always upgrade your plan if you need any additional features that meet your business needs.