Top 10 Free APIs Every Developer Should Bookmark (2026 Edition)

Every side project hits the same wall: you need data or functionality, but paid APIs eat into your $0 budget.

I maintain 31 free APIs on Cloudflare Workers. Here are 10 that solve real problems -- all with generous free tiers (500 req/month) and zero setup complexity.

1. QR Code Generator API

Generate QR codes in under 50ms. PNG, SVG, or Base64 with custom colors.

curl "https://qr-code-api.t-mizuno27.workers.dev/generate?text=https://example.com&format=png"

Use case: Event check-in systems, restaurant menus, business cards.

Try it on RapidAPI

2. Email Validation API

MX verification + disposable email detection (500+ domains) + typo correction. No emails sent.

import requests
resp = requests.get(
    "https://email-validation-api.t-mizuno27.workers.dev/validate/test@gmail.com",
    headers={"X-RapidAPI-Key": "YOUR_KEY"}
)
print(resp.json())  # {"valid": true, "disposable": false, ...}

Use case: Registration forms, newsletter cleanup, lead validation.

Try it on RapidAPI

3. SEO Analyzer API

19-point SEO audit with weighted scoring (0-100) for any URL. One API call replaces a $99/mo Ahrefs subscription for on-page analysis.

curl "https://seo-analyzer-api.t-mizuno27.workers.dev/analyze?url=https://your-site.com"

Use case: CI/CD SEO checks, content audits, competitor analysis.

Try it on RapidAPI

4. Text Analysis API (NLP)

Sentiment analysis, keyword extraction, readability scoring -- all without external AI APIs. Pure JavaScript NLP on the edge.

Use case: Content moderation, review analysis, writing tools.

Try it on RapidAPI

5. IP Geolocation API

Country, city, timezone, ISP + VPN/proxy detection. Supports bulk lookups (20 IPs at once).

Use case: Fraud detection, content localization, analytics enrichment.

Try it on RapidAPI

6. Currency Exchange Rate API

ECB-sourced rates for 30+ currencies. Real-time + historical data back to 1999.

Use case: E-commerce pricing, travel apps, financial dashboards.

Try it on RapidAPI

7. Web Metadata Extractor API

Extract OGP, Twitter Cards, JSON-LD, and meta tags from any URL. Like Slack link unfurling, but as an API.

const resp = await fetch("https://web-meta-extractor-api.t-mizuno27.workers.dev/extract?url=https://github.com");
const { metadata } = await resp.json();
console.log(metadata.ogTitle, metadata.ogImage);

Use case: Link previews, social media tools, content aggregation.

Try it on RapidAPI

8. Trends Aggregator API

The only API that pulls trending topics from Google Trends, Hacker News, Reddit, GitHub, and Product Hunt in one place.

Use case: Content calendars, trend monitoring, newsletter curation.

Try it on RapidAPI

9. AI Translation API (100+ Languages)

Neural machine translation via Meta M2M-100 model on Cloudflare Workers AI. No Google/DeepL API key needed.

Use case: User-generated content translation, multilingual apps, localization pipelines.

Try it on RapidAPI

10. Readability Score API

6 readability algorithms (Flesch, Gunning Fog, SMOG, etc.) in one call. Under 20ms response time.

resp = requests.post(
    "https://readability-score-api.t-mizuno27.workers.dev/analyze",
    json={"text": "Your article text here..."}
)
print(resp.json()["summary"]["avg_grade_level"])  # 8.2

Use case: CMS content checks, writing assistants, educational platforms.

Try it on RapidAPI

Why These Are All Free

Every API runs on Cloudflare Workers free tier -- 100K requests/day, zero hosting cost. I can offer generous free tiers because my infrastructure cost is literally $0/month.

The free tier (500 req/month) is enough for prototyping and small projects. Paid plans start at $4.99/month for production workloads.

What free APIs are essential in your toolkit? Drop them in the comments.