This document provides an overview of how to get started with the SimilarWeb API. It discusses signing up for a free trial account, making API requests, and monitoring usage. The API allows users to retrieve web traffic and engagement data, mobile app details, and related websites for a given domain. Requests require a domain, endpoint, format, and user key. Time granularity and date ranges can also be specified for some endpoints. Usage is monitored and quotas tracked to avoid going over limits.