APIs (Application Programming Interfaces) have revolutionized software development by allowing applications to communicate with external services seamlessly. Whether you are working on a web application, mobile app, chatbot, or data analytics platform, free public APIs can save development time and enhance functionality without extra costs.
In this article, we explore the 10 best free public APIs that every developer should consider in 2026, covering categories such as weather, finance, AI, space, geolocation, and more.
1. OpenWeather API
Best for: Weather Forecasting and Climate Data
The OpenWeather API provides real-time and historical weather data, including forecasts and air pollution levels. It is widely used in travel apps, farming applications, smart home automation, and fitness applications.
Key Features:
✅ Real-time weather updates from over 200,000 cities worldwide
✅ Hourly and daily forecasts for up to 16 days
✅ Historical data available for analysis
✅ Air pollution levels and UV index data
✅ Free tier allows 60 API calls per minute
Limitations:
- Some features, such as historical data beyond 1 year, require a paid subscription.
Use Case:
A mobile app can use OpenWeather API to send weather alerts and recommend outdoor activities based on forecasts.
API Documentation: https://openweathermap.org/api
2. CoinGecko API
Best for: Cryptocurrency Price Tracking
The CoinGecko API is a go-to solution for developers creating financial applications, trading platforms, and crypto tracking tools. It provides real-time cryptocurrency prices, market trends, and historical data.
Key Features:
✅ Live prices for over 12,000 cryptocurrencies
✅ Market data from 500+ exchange platforms
✅ Historical price charts and coin market trends
✅ Free tier allows 50 API calls per minute
Limitations:
- Rate limits apply, and advanced data points (e.g., derivatives, indices) require premium access.
Use Case:
A trading app can integrate the CoinGecko API to display live Bitcoin and Ethereum prices and track user portfolios.
🔗 API Documentation: https://www.coingecko.com/en/api
3. Unsplash API
Best for: Free High-Resolution Images
The Unsplash API provides access to millions of high-quality stock images. It is ideal for developers building blogs, design apps, social media platforms, and e-commerce websites.
Key Features:
✅ Over 3 million free images from professional photographers
✅ Search and filter images by categories and tags
✅ No watermark or attribution required
✅ Free tier allows 5,000 requests per hour
Limitations:
- Cannot use the API for bulk image downloads or resell the images.
Use Case:
A graphic design platform can fetch beautiful background images for user-generated content.
🔗 API Documentation: https://unsplash.com/developers
4. OpenAI API (GPT-4 & DALL·E)
Best for: AI-Powered Chatbots and Image Generation
The OpenAI API gives access to state-of-the-art natural language processing (GPT-4) and image generation (DALL·E) models, perfect for AI-driven applications.
Key Features:
✅ AI-powered text generation, summarization, and translations
✅ Code completion and bug detection
✅ AI-generated images from text prompts
✅ Free tier includes limited monthly credits
Limitations:
- Usage beyond the free tier requires purchase of OpenAI tokens.
- Some functionalities (e.g., voice synthesis) require API credits.
Use Case:
A company can use GPT-4 to power an AI chatbot that automates customer support queries.
🔗 API Documentation: https://openai.com/api
5. REST Countries API
Best for: Country and Geographic Data
The REST Countries API provides information about countries, their flags, currencies, and languages, making it useful for travel, finance, and education apps.
Key Features:
✅ 250+ countries’ data
✅ Country borders, capitals, and regions
✅ National flags, currencies, and calling codes
✅ Free tier allows unlimited API requests
Limitations:
- Data updates depend on external sources, so accuracy may vary.
Use Case:
A travel app can use this API to show country details when users select a destination.
🔗 API Documentation: https://restcountries.com
6. NASA Open APIs
Best for: Space and Astronomy Data
NASA provides free access to space imagery, asteroid tracking, and astronomical data, perfect for educational and science-related applications.
Key Features:
✅ NASA’s space imagery and satellite data
✅ Mars Rover images and asteroid tracking
✅ Astronomy Picture of the Day (APOD)
✅ Free tier supports unlimited API requests
Use Case:
A space blog can automatically fetch NASA’s Astronomy Picture of the Day and display it with explanations.
🔗 API Documentation: https://api.nasa.gov
7. IPinfo API
Best for: IP Address and Geolocation Services
The IPinfo API provides detailed IP address data, including geolocation, ISP information, and security threat detection.
Key Features:
✅ IP geolocation and ASN lookup
✅ Detection of VPN/proxy usage
✅ Free tier includes 50,000 requests per month
Use Case:
An e-commerce platform can use IPinfo to show region-specific content based on user location.
🔗 API Documentation: https://ipinfo.io/developers
8. The Dog API & The Cat API
Best for: Pet and Fun Apps
Both The Dog API and The Cat API offer fun animal images for entertainment and pet-related apps.
Key Features:
✅ Thousands of high-quality pet images
✅ Breed filtering and categorization
✅ Free tier includes unlimited requests
🔗 API Documentation:
- Dog API: https://thedogapi.com
- Cat API: https://thecatapi.com
9. Open Library API
Best for: Books and Literature Apps
The Open Library API offers access to millions of books and author data for educational, reading, and research applications.
Key Features:
✅ 20+ million books with metadata
✅ Book covers, descriptions, and author details
✅ Free tier allows unlimited API requests
🔗 API Documentation: https://openlibrary.org/developers/api
10. Jokes API
Best for: Fun and Entertainment Apps
The Jokes API provides a collection of humorous content that can be used in chatbots, websites, and social media apps.
Key Features:
✅ Thousands of categorized jokes
✅ JSON format for easy integration
✅ Free tier with unlimited API requests
🔗 API Documentation: https://v2.jokeapi.dev
Final Thoughts
These 10 free public APIs offer great functionality for developers without the need for paid plans. Whether you are working on weather forecasting, AI-powered tools, space exploration, or just fun projects, these APIs can significantly enhance your applications.