12 Best Free Public APIs for Side Projects

Public APIs let a small project work with useful information without building every dataset yourself. This list is for students, hobby developers, and freelancers who want something real to display in a prototype or portfolio.

The services below cover topics from forecasts to books and intentionally simple sample records. Free access and usage rules can change, so read the provider's current documentation before putting an API into a public or business-facing product.

Quick picks

• Best overall: Open-Meteo — weather data with a straightforward, key-free start.
• Best for learning: JSONPlaceholder — predictable sample responses for practising requests.
• Best for geography: REST Countries — useful country facts for forms and demos.
• Best for book projects: Open Library — search and catalogue information from a large public resource.

How we picked

We looked for recognizable APIs with clear documentation, useful data, and a realistic path to trying them in a small project. “Free” does not mean unlimited or suitable for every commercial use, so check terms and service limits before launch.

• Useful output: the response can power a visible feature, not just a toy call.
• Low setup: beginners can make a first request without complicated infrastructure.
• Documentation: examples and field descriptions help explain the response.
• Responsible use: providers' rate limits and attribution rules are easy to locate.

Everyday data

1. Open-Meteo

Open-Meteo provides weather forecasts and historical weather data, with location-based queries that suit a small dashboard or trip-planning demo. Its no-key entry point makes it easy to explore from a browser or a simple app, and the range of weather variables is a real advantage. Forecasts are not a substitute for emergency alerts, and usage terms vary by use case. Free access is available under stated conditions.

Best for: student projects that show local forecast details without managing an API key.

2. REST Countries

REST Countries returns country information such as names, flags, regions, currencies, and languages. It is a practical source for a country picker, geography quiz, or data-display exercise, and the mix of fields gives beginners plenty to practise filtering. It is a community-maintained service, so do not assume every field is a definitive authority or that the service guarantees production uptime. Free public access is available.

Best for: forms and learning projects that need country names, flags, or regional facts.

3. Frankfurter

Frankfurter serves foreign-exchange reference rates and supports requests for conversions and historical dates. That makes it handy for a personal finance mock-up or a clear example of working with dates and numeric data. Reference rates are not live trading quotes, and the service is not a payments or financial advice provider. It is free to use, with the data source and limitations described in its documentation.

Best for: currency-conversion demos where indicative reference rates are enough.

4. Nager.Date

Nager.Date offers public-holiday data across supported countries, including dates and holiday names. Developers can use it to populate a calendar or display upcoming days off without hand-entering every national date. Coverage and local observances may differ, so verify important dates against an official government source; regional holidays are not guaranteed to be comprehensive. The public API is free.

Best for: calendar projects that need a quick starting list of national holidays.

Playful and test data

5. JSONPlaceholder

JSONPlaceholder is a deliberately simple fake REST service with posts, users, comments, albums, and related records. Its familiar resource structure makes it excellent for learning fetch calls, loading states, and basic pagination-like interface patterns. Writes are simulated rather than saved as a real application's data, which is an important limitation when testing persistence. It is free and intended for testing and examples.

Best for: beginners building a front end before their own backend exists.

6. PokeAPI

PokeAPI exposes a large catalogue of Pokémon-related records, including species, moves, abilities, and game details. Its connected resources are useful for practising nested data and building a collection browser or quiz. The dataset has a specialised subject and can take some exploration to understand; it is not a general-purpose product database. The API is free, and its documentation explains how to navigate the records.

Best for: playful portfolio apps that make learning API relationships more engaging.

7. The Cat API

The Cat API supplies cat images and related breed information, making a visual gallery easy to assemble. The image-focused response is a nice way to practise asynchronous loading and empty states, while breed records add a small discovery feature. Some functionality may require an account or key, and image availability is not a guarantee of consistent content. A free tier is offered with paid options for broader use.

Best for: a lightweight image gallery or breed explorer with an approachable theme.

8. Dog CEO API

Dog CEO API is a simple source of dog images, including endpoints for breeds and random pictures. It is particularly friendly for a first client-side experiment because a response can become a visible feature in very little code. It is image data rather than a rich animal reference database, and requests can still fail or return unexpected results. The service is free to use.

Best for: first-time API learners who want a fun result on screen quickly.

Search and developer data

9. Open Library

Open Library offers book catalogue records and search access connected to a public library project. A reading-list prototype can use it to find titles, authors, and cover information rather than maintaining its own catalogue. Records vary in completeness, and a catalogue entry should not be treated as a guarantee that a book is available to borrow. The service is free; consult its API guidance and usage expectations.

Best for: book discovery projects and reading trackers that need searchable catalogue data.

10. GitHub REST API

The GitHub REST API provides access to public repositories, issues, users, and other GitHub resources. It can power a portfolio widget or a project explorer, and its official documentation is unusually detailed. Unauthenticated and authenticated requests have limits, and private information requires proper authorisation; never expose a personal access token in browser code. Public API access is free within the applicable limits.

Best for: developer dashboards that present public repository activity or project details.

11. Wikipedia REST API

The Wikimedia REST API offers access to encyclopaedia-related content such as page summaries. It can support a learning demo or a contextual information panel, with a vast subject range as its obvious strength. Content is collaboratively edited and may need review before reuse; follow Wikimedia's attribution and request guidance. Public access is available without a paid plan, subject to service policies.

Best for: educational prototypes that need short background summaries on many subjects.

12. DummyJSON

DummyJSON provides sample products, users, posts, and other records for prototyping. Its variety makes it convenient when a mock shop or dashboard needs structured content before a real data source is ready. The records are fictional sample data, not current product listings or user accounts, and write behaviour is for demonstration rather than a lasting database. It is free to use.

Best for: interface builders who need a varied set of believable sample records.

How to choose the right one

Start with the feature you want someone to try: a forecast card needs weather, while a book search needs catalogue records. Read the API's terms, rate limits, and attribution guidance before investing in a design. Check whether it needs a key, and keep any secret credential on a server rather than shipping it in front-end code. For a prototype, call the endpoint with a few realistic inputs and inspect missing fields as well as successful responses. Our API latency tester can help you compare response times while you evaluate a service. If you are building a broader developer workflow, browse Stockio's development resources and API testing tools guide.

Key takeaways

• Choose data that supports a clear user feature, rather than picking an API only because it is easy to call.
• JSONPlaceholder and DummyJSON are convenient for interface practice, but their records are not production data.
• Check limits, licences, and attribution before a public launch.
• Protect credentials by keeping private keys out of browser applications.
• Plan for failure: show a useful empty or error state when a public service is unavailable.