PoeticMetric allows you to track the performance of your website. It requires a javascript snippet to be added to the pages that will be tracked. This injected javascript snippets sends the required information to PoeticMetric's REST API when a visitor visits your website, and the collected data is processed and aggregated to generate the reports.
You can track unlimited number of websites, however, the number of page views (or events) you can use changes according to your subscription plan. See pricing for details.