RPC API: provided for developers transitioning applications from Etherscan to Blockscout. Supports GET and POST requests, simply replace Etherscan url with Blockscout url to use the RPC.
API Keys are not needed by default. Blockscout instances have a standard global request setting of 10/requests per second. However, My Account users can add up to 3 API keys to ensure 10 request/second limits per account.