Public APIs: Open the Repo and Start Building

Need a free API for a prototype, a hackathon, or a portfolio project? Stop Googling one at a time. There is a community-curated directory with hundreds of public APIs, and you can start using it right now.

What it is

Public APIs is a GitHub repository that lists public APIs across many domains: weather, finance, security, machine learning, programming, open data, test data, and more. Each API entry includes a description, the authentication requirement, whether it supports HTTPS, and its CORS status. The list is manually curated by community members, and at research time the repo had about 443,000 stars and 48,500 forks.

It is essentially a phone book for APIs. Instead of searching for "free weather API" and sorting through dead links and outdated blog posts, you open the repo, find the category you need, check the Auth, HTTPS, and CORS columns, and pick an API that fits your project.

Why it matters

• It saves time when you need sample data for a side project, demo, or hackathon. Instead of building a backend or finding a dataset, you grab a real API and start building.
• It helps junior developers quickly understand which APIs need a key and which can be called immediately, because the Auth column tells you upfront.
• The categories span from weather and finance to security, machine learning, and test data, so there is something for almost any prototype idea.
• The Auth, HTTPS, and CORS columns make it easy to filter for APIs that work well in frontend applications without a proxy.

How it works

Using the repo is a three-step process. First, open the README and find the category that matches your needs. If you are building a weather app, go to Weather. If you are building a finance dashboard, go to Finance. Prioritize APIs with HTTPS and simple authentication. Second, do not just copy and paste. Open the original documentation for the API, test the endpoint with curl, Postman, or a simple fetch call, and verify that the response is what you expect, the quota is clear, and the data fits your use case. Third, integrate it into a small app first, with loading states, error handling, and fallback data, so your demo does not die just because a public API is slow or down.

Caveats

This repo is a directory, not a reliability guarantee. Not every listed API is stable or still free. Some entries may be outdated, with changed domains, updated pricing, or new rate limits. Before shipping anything to production, you need to read the original docs, test the rate limits, check the data license, and verify the uptime. A high star count on the repo does not mean every listed API is production-ready.

Who it's for

This is for developers who build fast: portfolio projects, hackathon prototypes, frontend mockups, API learning exercises, or AI agent tool testing. It is a starting point for finding data, not a production dependency. If you are a developer who likes to build quickly, bookmark the repo and try one API in a small project today.