JSON Placeholder is a service that provides you with fake online REST APIs for testing and prototyping. This is a go-to API for every developer.
Link: https://jsonplaceholder.typicode.com/
2. Google Translate
Google has a plethora of APIs, but most of them are paid. Thankfully, the Translate API provides free translations for 100+ languages, up to 500k characters per month.
Link: https://cloud.google.com/translate/docs/
3. Open Weather Map
Need to look into the crystal ball & predict the weather? Open Weather Map is a service that does just that & provides you easy access to their data via their API.