Best APIs for Developers: Complete Guide

APIs are the backbone of modern software development. They allow applications to communicate, share data, and leverage third-party services. This guide covers the best APIs across various categories.

Useful Resources

Public APIs Repository - Curated list of free APIs
RapidAPI Hub - API marketplace
Postman API Network - Explore and test APIs

AI and Machine Learning APIs

AI API Ecosystem

Overview

API	Pricing	Free Tier	Best For
OpenAI	Pay-per-token	$5 credit	GPT-4, DALL-E, Whisper
Google Cloud AI	Pay-as-you-go	$300 credit	Vision, Speech, Translation
Hugging Face	Free + Pro $9/mo	Rate-limited	200K+ open source models

OpenAI API

The most powerful AI API for language models, image generation, and speech.

Feature	Details
Models	GPT-4, GPT-4 Turbo, DALL-E 3, Whisper
Pricing	From $0.002/1K tokens
Documentation	platform.openai.com/docs

const response = await openai.chat.completions.create({
  model: "gpt-4",
  messages: [{ role: "user", content: "Hello!" }]
});

Google Cloud AI

Comprehensive suite of AI services.

Feature	Details
Products	Vision, Speech-to-Text, Natural Language, Translation
Pricing	Pay-as-you-go
Documentation	cloud.google.com/apis

Hugging Face

Access 200,000+ open-source ML models.

Feature	Details
Models	NLP, Computer Vision, Audio
Pricing	Free tier + Pro from $9/month
Documentation	huggingface.co/docs

Payment APIs

Payment API Ecosystem

Overview

API	Transaction Fee	Free Tier	Best For
Stripe	2.9% + $0.30	Free to integrate	Subscriptions, marketplaces
PayPal	2.99% + fee	Sandbox	International payments
Plaid	Custom pricing	100 dev items	Bank account connectivity

Stripe

Industry standard for online payments.

Feature	Details
Currencies	135+ supported
Features	Subscriptions, Connect, Radar fraud protection
Documentation	stripe.com/docs

const paymentIntent = await stripe.paymentIntents.create({
  amount: 2000,
  currency: 'usd',
});

PayPal

Global payment solution with buyer protection.

Feature	Details
Features	Checkout, Subscriptions, Payouts, Invoicing
Documentation	developer.paypal.com

Plaid

Bank account connectivity for fintech apps.

Feature	Details
Use Cases	Account verification, transactions, balances
Documentation	plaid.com/docs

Communication APIs

Communication API Platform

Overview

API	Free Tier	Pricing	Best For
Twilio	$15 credit	SMS from $0.0079	SMS, Voice, Video
SendGrid	100 emails/day	From $19.95/mo	Email delivery
Resend	3K emails/month	From $20/mo	React Email templates

Twilio

SMS, voice, video, and WhatsApp messaging.

Feature	Details
Channels	SMS, MMS, Voice, Video, WhatsApp
Documentation	twilio.com/docs

const message = await client.messages.create({
  body: 'Hello from Twilio!',
  from: '+1234567890',
  to: '+0987654321'
});

SendGrid

Email delivery for transactional and marketing emails.

Feature	Details
Features	Templates, Analytics, Delivery optimization
Documentation	docs.sendgrid.com

Resend

Modern email API with excellent developer experience.

Feature	Details
Features	React Email support, Analytics
Documentation	resend.com/docs

Authentication APIs

Overview

API	Free Tier	Pricing	Best For
Auth0	7,500 MAU	From $23/mo	Enterprise, SSO
Clerk	10,000 MAU	From $25/mo	Next.js apps
Firebase Auth	10K verifications	Pay-as-you-go	Mobile apps

Auth0

Feature	Details
Features	Universal Login, Social connections, MFA, SSO, RBAC
Documentation	auth0.com/docs

Clerk

Feature	Details
Features	Pre-built components, Session management
Documentation	clerk.com/docs

Firebase Authentication

Feature	Details
Providers	Email, Phone, Google, Apple, Facebook, GitHub
Documentation	firebase.google.com/docs/auth

Data and Analytics APIs

Overview

API	Free Tier	Pricing	Best For
Mixpanel	20M events/mo	From $25/mo	Product analytics
Segment	1K visitors/mo	From $120/mo	Data collection
Amplitude	10M events/mo	Free Starter	Behavioral cohorts

Weather and Location APIs

Overview

API	Free Tier	Pricing	Best For
OpenWeatherMap	1K calls/day	From $40/mo	Weather data
Mapbox	50K loads/mo	Pay-as-you-go	Custom maps
Google Maps	$200 credit/mo	Pay-as-you-go	Directions, Places

OpenWeatherMap

Feature	Details
Data	Current weather, Forecasts, Historical, Alerts
Documentation	openweathermap.org/api

fetch(`https://api.openweathermap.org/data/2.5/weather?q=London&appid=${KEY}`)

Mapbox

Feature	Details
Products	Maps SDK, Geocoding, Directions, Isochrone
Documentation	docs.mapbox.com

Google Maps Platform

Feature	Details
APIs	Maps JS, Places, Directions, Geocoding, Street View
Documentation	developers.google.com/maps

Media APIs

Overview

API	Free Tier	Pricing	Best For
Cloudinary	25 credits/mo	From $99/mo	Image/video processing
Spotify	Rate-limited	Free	Music data
TMDB	Full access	Free	Movie/TV data

Cloudinary

Feature	Details
Features	Auto-optimization, Transformations, CDN, AI tagging
Documentation	cloudinary.com/documentation

Spotify Web API

Feature	Details
Data	Tracks, Albums, Artists, Playlists, Audio features
Documentation	developer.spotify.com

TMDB

Feature	Details
Data	Movies, TV shows, Cast, Images, Ratings
Documentation	developer.themoviedb.org

Developer Utility APIs

Overview

API	Free Tier	Pricing	Best For
GitHub	5K req/hr	Free	Repository management
Algolia	10K searches/mo	From $1/1K	Site search
Sentry	5K errors/mo	From $29/mo	Error tracking

GitHub API

Feature	Details
Features	Repos, Issues, PRs, Actions, Search
Documentation	docs.github.com/rest

Algolia

Feature	Details
Features	Typo-tolerance, Faceted search, Analytics
Documentation	algolia.com/doc

Sentry

Feature	Details
Features	Error tracking, Performance, Releases, Source maps
Documentation	docs.sentry.io

E-commerce APIs

Overview

API	Free Tier	Pricing	Best For
Shopify	Dev stores free	Free for partners	Store integrations
Printful	No monthly fees	Pay per product	Print-on-demand

Social Media APIs

Overview

API	Free Tier	Pricing	Best For
Twitter/X	1.5K tweets/mo	Basic $100/mo	Social tools
Meta Graph	Rate-limited	Free	Facebook, Instagram

Free Public APIs

API	Description	URL
JSONPlaceholder	Fake REST API for testing	jsonplaceholder.typicode.com
PokeAPI	Pokemon data	pokeapi.co
REST Countries	Country information	restcountries.com
NASA APIs	Space data and images	api.nasa.gov
CoinGecko	Cryptocurrency data	coingecko.com/api
RandomUser	Random user generator	randomuser.me

API Selection Criteria

Factor	Questions to Ask
Pricing	Free tier limits? Pay-as-you-go vs subscription?
Reliability	Uptime SLA? Status page history?
Documentation	Clear examples? SDKs for your language?
Security	Auth methods? Compliance certifications?
Support	Response time? Community forums?

Best Practices

Environment Variables

const apiKey = process.env.API_KEY;

Error Handling

try {
  const response = await fetch(url);
  if (!response.ok) throw new Error(`HTTP ${response.status}`);
} catch (error) {
  console.error('API Error:', error);
}

Rate Limiting - Implement client-side limits

Caching - Cache responses when appropriate

Monitoring - Track usage and costs