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Jack
Jack

Posted on • Originally published at anethoth.com

7 Free APIs You Can curl Right Now (No Signup, No API Key)

#api #webdev #productivity #beginners

Sometimes you just need a quick API to test something, format data, or solve a problem. No signup forms. No API keys. No OAuth dance.

Here are 7 free APIs you can hit right now from your terminal.

1. Convert HTML to PDF 

curl -X POST https://documint.anethoth.com/api/v1/html-to-pdf \
  -H "Content-Type: application/json" \
  -d '{"html": "<h1>Hello World</h1><p>This is a PDF.</p>"}' \
  --output test.pdf
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Accepts raw HTML, returns a PDF. Supports A4, Letter, Legal page sizes. Great for generating reports from HTML templates.

2. Convert Markdown to PDF 

curl -X POST https://documint.anethoth.com/api/v1/markdown-to-pdf \
  -H "Content-Type: application/json" \
  -d '{"markdown": "# Report\n\n## Summary\n\nAll systems operational.\n\n- Server: ✅\n- Database: ✅\n- Cache: ✅"}' \
  --output report.pdf
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Perfect for turning README-style markdown into formatted PDFs. Handles headings, lists, code blocks, tables.

3. Parse Cron Expressions 

curl "https://cronping.anethoth.com/api/v1/cron/describe?expr=0+9+*+*+1-5"
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Returns: "At 09:00, Monday through Friday". Never guess what a cron expression does again.

4. Get Next Cron Run Times 

curl "https://cronping.anethoth.com/api/v1/cron/next?expr=0+*/6+*+*+*&count=5"
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Shows the next 5 times a cron job would fire. Useful for debugging scheduling issues.

5. Validate Cron Syntax 

curl "https://cronping.anethoth.com/api/v1/cron/validate?expr=0+0+31+2+*"
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Returns whether the expression is valid with field breakdown. Catch syntax errors before they hit production.

6. Echo Any HTTP Request 

curl -X POST https://webhookvault.anethoth.com/api/v1/echo \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer test123" \
  -d '{"key": "value"}'
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Mirrors your entire request back as JSON — method, headers, body, IP, timestamp. Invaluable for debugging HTTP clients, proxies, or load balancers.

7. Inspect Your Request Headers 

curl https://webhookvault.anethoth.com/api/v1/headers
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Shows all headers your request sent, plus analysis: auth type detection, proxy detection, CORS origin. Great for debugging "why isn't my auth header being sent" issues.

Bonus: Simulate Feature Flag Rollouts 

curl "https://flagbit.anethoth.com/api/v1/rollout/simulate?flag=new-feature&percentage=25&user_count=100"
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Simulates which users would be included in a percentage rollout using consistent hashing. Useful for planning gradual rollouts.

All of these are completely free, no rate limit anxiety (60 req/min), and CORS-enabled so you can use them from the browser too.

I built these as part of Anethoth — a collection of developer tools. The free APIs are genuinely free forever, not a trial.

What free APIs do you use regularly? I'm always looking for useful tools to add to my toolkit.

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