I Built 25 Cloudflare Workers APIs — Here's What I Learned

Over the past few months, I built and deployed 25 APIs on Cloudflare Workers. All running on the free tier. Total monthly hosting cost: $0.

Here's what I learned about building, deploying, and monetizing utility APIs at scale.

The Stack

Every API follows the same pattern:

worker-api/ ├── src/ │ └── index.js # Single entry point ├── wrangler.toml # Cloudflare config └── package.json

worker-api/ ├── src/ │ └── index.js # Single entry point ├── wrangler.toml # Cloudflare config └── package.json

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No frameworks. No bundlers. Just vanilla JavaScript on Cloudflare Workers.

The 25 APIs

Here's a sampling of what I built:

API Purpose Complexity

Readability Score Text analysis (Flesch-Kincaid, SMOG, ARI) Medium

QR Code Generator Generate QR codes from text/URL Low

Password Generator Cryptographically secure passwords Low

Markdown to HTML CommonMark-compliant conversion Medium

Color Converter HEX/RGB/HSL conversion Low

Base64 Encoder Encode/decode Base64 Low

JSON Formatter Pretty-print & validate JSON Low

URL Shortener Create short URLs Medium

Hash Generator MD5, SHA-1, SHA-256, SHA-512 Low

Timezone Converter Convert between timezones Medium

Email Validator Syntax + MX record validation Medium

IP Geolocation IP to country/city lookup Medium

Currency Exchange Real-time exchange rates High

Text Summarizer Extractive summarization High

SEO Analyzer On-page SEO scoring High

All listed on RapidAPI.

5 Lessons Learned

1. One endpoint is better than ten

My most-used APIs have one endpoint. Send data, get results. No complex auth flows, no pagination, no state management.

export default {  async fetch(request) {  const { text } = await request.json();  const result = analyze(text);  return Response.json(result);  } };

export default {  async fetch(request) {  const { text } = await request.json();  const result = analyze(text);  return Response.json(result);  } };

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2. The free tier is generous (but has gotchas)

Cloudflare Workers free tier:

• ✅ 100,000 requests/day

• ✅ 10ms CPU time per request

• ❌ No KV storage (need paid plan)

• ❌ No Durable Objects

For stateless computation APIs, the free tier is perfect. For anything needing storage, you'll hit limits fast.

3. Error handling is 80% of the code

The actual logic for most APIs is 20-30 lines. Input validation, error messages, edge cases, and CORS handling make up the rest.

// Validation pattern I use everywhere if (!text || typeof text !== 'string') {  return Response.json(  { error: 'Missing required field: text' },  { status: 400 }  ); } if (text.length > 10000) {  return Response.json(  { error: 'Text exceeds 10,000 character limit' },  { status: 413 }  ); }

// Validation pattern I use everywhere if (!text || typeof text !== 'string') {  return Response.json(  { error: 'Missing required field: text' },  { status: 400 }  ); } if (text.length > 10000) {  return Response.json(  { error: 'Text exceeds 10,000 character limit' },  { status: 413 }  ); }

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4. Documentation sells APIs

The APIs with the most subscribers on RapidAPI aren't the most complex — they're the best documented. Clear examples, realistic response samples, and a "try it" button.

5. Bundle related APIs, don't build monoliths

I started with a "Swiss Army Knife API" that did everything. Nobody used it. When I split it into focused, single-purpose APIs, subscriptions went up.

Deployment Workflow

# Deploy all 25 APIs for dir in workers/*/; do  cd "$dir"  wrangler deploy  cd .. done

# Deploy all 25 APIs for dir in workers/*/; do  cd "$dir"  wrangler deploy  cd .. done

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Each API deploys in under 5 seconds. Total deployment time for all 25: ~2 minutes.

What's Next

I'm expanding to 30+ APIs by Q2 2026. The pattern is proven — the marginal cost of adding a new API is near zero.

If you're looking for utility APIs, check them out on RapidAPI.

What APIs have you built on Cloudflare Workers? I'd love to hear about your experience with the platform.