The legacy IPinfo public API is available and supported without an account:
Here's how to use it:
curl https://ipinfo.io/json
However, this service is limited to 1,000 requests per day, and the limit is shared across everyone using the same IP address. This means you can run into random rate limits.
Signing up for the free IPinfo Lite plan provides unlimited requests with no daily or monthly cap. An IPinfo account also includes access to the Dashboard, with tools like lookup history, starred IPs, bulk lookups, usage statistics, and product upgrade options.