5 Free APIs Every Developer Should Know About in 2026

Source: Dev.to

Building side projects? You know the pain — most useful data APIs either cost $50+/month or have laughably small free tiers.

I built a suite of 5 free APIs for the data developers actually need. Each one has a free tier of 100 requests/day (enough for prototyping and small apps), and paid tiers starting at $9.99/month if you need more. All are hosted on RapidAPI with full documentation and code examples.

Currency Exchange Rate API

What

Real-time and historical exchange rates for 31 currencies, sourced from the European Central Bank.

Endpoints

• Latest rates
• Historical rates (back to 1999)
• Currency conversion
• Time series
• Supported currencies list

Why it’s different

Most currency APIs charge $15‑50/month for basic access. This one is free for 100 req/day and $9.99/month for production use. Sub‑50 ms response times on Cloudflare’s edge network.

Use it for

Currency converters, multi‑currency e‑commerce, finance dashboards, travel apps.

Try it

Currency Exchange Rate API on RapidAPI

const response = await fetch('https://currency-exchange-rates13.p.rapidapi.com/rates/latest', {
  headers: {
    'x-rapidapi-key': 'YOUR_KEY',
    'x-rapidapi-host': 'currency-exchange-rates13.p.rapidapi.com'
  }
});
const data = await response.json();
console.log(data.rates.USD); // 1.0842

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Air Quality Index (AQI) API

What

Real-time air quality data for any city — AQI score, individual pollutant readings (PM2.5, PM10, O₃, NO₂, SO₂, CO), and health recommendations.

Endpoints

• Current AQI by city
• City pollution rankings
• Historical data
• Health advice

Why it’s different

Most AQI APIs just give you a number. This one includes health recommendations in every response (e.g., “Sensitive groups should limit outdoor exertion”) and lets you rank cities by pollution levels.

Use it for

Weather apps, health trackers, smart home dashboards, data‑visualization projects.

Try it

Air Quality Index API on RapidAPI

import requests

url = "https://air-quality-index2.p.rapidapi.com/current"
querystring = {"city": "London"}
headers = {
    "x-rapidapi-key": "YOUR_KEY",
    "x-rapidapi-host": "air-quality-index2.p.rapidapi.com"
}
response = requests.get(url, headers=headers, params=querystring)
print(response.json())

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UV Index & Sun Exposure API

What

Current UV index, 7‑day hourly forecast, and — the unique part — safe sun exposure times calculated by Fitzpatrick skin type with vitamin D synthesis estimates.

Endpoints

• Current UV
• Forecast
• Safe exposure calculator
• Vitamin D estimates
• Historical UV data

Why it’s different

No other UV API calculates personalized safe exposure times for all 6 Fitzpatrick skin types or estimates vitamin D production. It’s health data, not just weather data.

Use it for

Health/fitness apps, travel planners, dermatology tools, outdoor‑sports platforms.

Try it

UV Index & Sun Exposure API on RapidAPI

curl -X GET "https://uv-index-sun-exposure.p.rapidapi.com/uv/current?lat=40.7128&lng=-74.006" \
  -H "x-rapidapi-key: YOUR_KEY" \
  -H "x-rapidapi-host: uv-index-sun-exposure.p.rapidapi.com"

---

US Fuel & Energy Price API

What

Gas prices (regular, midgrade, premium, diesel) and electricity rates (residential, commercial, industrial) for all 50 US states. Historical data back to 1990.

Endpoints

• Current gas prices by state
• National averages
• Electricity rates by sector
• Historical trends

Why it’s different

35+ years of government‑sourced data (EIA) in one API. No other free‑tier API combines gas and electricity data. Great for data‑heavy projects.

Use it for

Fleet management, travel apps, real estate (utility‑cost comparisons), EV cost calculators, data journalism.

Try it

US Fuel & Energy Price API on RapidAPI

const response = await fetch('https://us-fuel-energy-prices.p.rapidapi.com/gas/prices/state/CA', {
  headers: {
    'x-rapidapi-key': 'YOUR_KEY',
    'x-rapidapi-host': 'us-fuel-energy-prices.p.rapidapi.com'
  }
});
const data = await response.json();
console.log(`California regular gas: $${data.regular}/gallon`);

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Sales Tax & VAT Validation API (Coming Soon)

What

US state/local sales tax rates, EU VAT rates, and Canadian GST/HST/PST — plus EU VAT number validation.

Use it for

E‑commerce checkout, invoicing, tax compliance, SaaS billing with regional tax handling.

Listing going live soon — follow Two Hundred OK on RapidAPI to get notified.

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Why I Built These

I kept running into the same problem: I needed simple data for a side project and every API was either expensive, unreliable, or had a 10‑request/day free tier. So I built a suite of APIs on Cloudflare Workers (global edge, fast responses) with genuinely useful free tiers.

All 5 APIs share the same design philosophy:

• Generous free tier (100 req/day — enough to prototype and run small apps)
• Simple, consistent JSON responses
• Official data sources (ECB, EIA, government APIs)
• Fast (Cloudflare edge, sub‑100 ms globally)

If you try any of them, I’d love to hear what you’re building. Drop a comment!