Here’s a curated list of 20 free APIs that can transform your side projects, whether you’re building a simple app, experimenting with AI, or just trying something new.

1. OpenAI API (Free Tier)
Create smarter, more interactive applications with AI at their core. OpenAI’s GPT models can handle tasks like writing text, summarizing articles, and even generating code. Their free tier is perfect for small experiments and side projects.

Use it for: Personal chatbots, productivity tools, or quirky text-based games.

https://platform.openai.com/docs/overview

2. Unsplash API
Designers and developers, this one’s for you. With Unsplash’s API, you get access to a treasure trove of high-quality, royalty-free images to use in your projects.

Use it for: Stunning blog visuals, photography apps, or creative portfolios.
https://unsplash.com/developers

3. WeatherAPI
Weather data doesn’t get more comprehensive than this. Real-time weather updates, historical data, and even advanced features like air quality or astronomy insights—all at your fingertips.

Use it for: Weather dashboards, trip planners, or IoT integrations.
https://www.weatherapi.com/

4. Spotify Web API
Turn your app into a music lover’s paradise. From playlists to album details, Spotify’s API gives you access to an incredible database of music metadata.

Use it for: Personalized playlists, music visualizers, or discovery tools.
https://developer.spotify.com/documentation/web-api

5. NASA APIs
Dreaming of space? NASA’s free APIs include everything from Mars rover photos to satellite imagery and celestial events. It’s like a backstage pass to the cosmos.

Use it for: Educational apps, astronomy trackers, or sci-fi-inspired visuals.
https://api.nasa.gov/

6. The Movie Database (TMDB) API
This API serves up detailed information on movies, TV shows, and celebrities. Plus, it includes high-quality posters and fan art.

Use it for: Entertainment apps, trivia games, or recommendation systems.
https://developer.themoviedb.org/reference/intro/getting-started

7. NewsAPI
Bring breaking news to your app with real-time articles from thousands of sources. Filter by language, category, or region to keep content relevant.

Use it for: News aggregators, trend trackers, or sentiment analysis tools.
https://newsapi.org/

8. REST Countries API
All the data you’ll ever need about the world’s nations—from population and GDP to flags and calling codes.

Use it for: Travel planners, world geography quizzes, or global stats dashboards.
https://restcountries.com/

9. OpenLibrary API
Calling all bookworms! OpenLibrary’s API provides metadata on millions of books, including authors, genres, and publication years.

Use it for: Book review platforms, reading trackers, or literary discovery apps.
https://openlibrary.org/developers/api

10. Random User Generator API
Need dummy data to test your project? This API creates random user profiles complete with photos, names, and even fake addresses.

Use it for: UI testing, prototype demos, or app mockups.
https://randomuser.me/

11. PokeAPI
Whether you’re nostalgic for Pokémon or just love building gaming apps, this API has all the data you need—from Pokémon stats to move sets and abilities.

Use it for: Games, trivia apps, or nostalgic side hustles.
https://pokeapi.co/

12. OpenWeatherMap API
Weather widgets, apps, and trackers have never been easier. This API simplifies fetching real-time and forecasted weather details.

Use it for: Custom weather trackers or time-sensitive notifications.
https://openweathermap.org/api

13. Public Holidays API
Never miss a day off again. Get public holiday data for almost any country around the world with just a few API calls.

Use it for: Event planners, payroll software, or calendar apps.
https://www.openholidaysapi.org/en/

14. QR Code Generator API
Quickly create dynamic QR codes for your apps, websites, or campaigns with this simple yet powerful API.

Use it for: Marketing tools, ticketing systems, or contactless interactions.
https://goqr.me/api/

15. Agify API
Want to predict someone’s age based on their first name? Agify uses data science to make eerily accurate guesses.

Use it for: Fun experiments, demographic analysis, or quirky app features.
https://agify.io/

16. ExchangeRate-API
Track currency conversions in real-time with this lightweight and beginner-friendly API.

Use it for: Travel calculators, finance dashboards, or budgeting apps.
https://www.exchangerate-api.com/

17. IP Geolocation API
This API takes an IP address and returns detailed location data, making it easy to personalize user experiences.

Use it for: Localization, analytics tools, or enhanced security.
https://geo.ipify.org/

18. OpenCage Geocoder API
Convert coordinates into readable addresses or vice versa with OpenCage’s accurate geocoding tools.

Use it for: Maps, delivery apps, or geographic analysis.
https://opencagedata.com/

19. Jikan API
If you’re into anime, Jikan is your go-to API. It pulls data straight from MyAnimeList, including anime, manga, and character details.

Use it for: Anime trackers, recommendation engines, or fandom apps.
https://jikan.moe/

20. Open Brewery DB
A directory of breweries worldwide, right at your fingertips.

Use it for: Brewery locators, travel apps, or just beer-inspired fun.
https://www.openbrewerydb.org/

These save time, reduce complexity, and let you focus on what matters—your creative ideas. With this list, you’ve got everything you need to start building.

So, which API are you trying first? Let me know in the comments.