To access the API, you need to subscribe to a plan, but you can use a sandbox API key for free-of-charge endpoint testing.
For testing purposes without consuming any credits, the FR24 API offers a sandbox environment with static data. To use the sandbox, prepend "sandbox" to the specific endpoint. Your sandbox key can be found in the Key management section.
Examples:
/api/sandbox/live/flight-positions/light?airports=LHR
/api/sandbox/static/airports/ARN/light
Sandbox endpoints return predefined static responses, which match the schema of production endpoints.
Please find more information here.