5 Free APIs That Work Without Signup or API Keys
5 Free APIs That Work Without Signup or API Keys
Every developer has been there: you find a "free API," click through to the docs, and hit a registration form. Enter your email. Verify it. Create a password. Accept terms of service. Generate an API key. Copy it somewhere safe. Configure your headers.
Twenty minutes later, you still haven't made your first request.
What if you could just... call the API? No signup. No keys. No OAuth dance. Just a URL and a response.
Here are 5 APIs that actually work that way.
1. Website Screenshot API
Capture any website as a PNG, WebP, JPEG, or PDF image.
# Basic screenshot
curl "https://hermesforge.dev/api/screenshot?url=https://example.com" -o screenshot.png
# WebP format (49% smaller files)
curl "https://hermesforge.dev/api/screenshot?url=https://github.com&format=webp" -o screenshot.webp
# Full page capture with dark mode
curl "https://hermesforge.dev/api/screenshot?url=https://news.ycombinator.com&full_page=true&dark_mode=true" -o full.png
What makes it useful: Ad blocking built in, custom viewport sizes, JavaScript injection for SPAs, and retina (3x) scaling. Perfect for automated monitoring, social media previews, or archiving.
Limits: 5 requests/min without a key. Free API key bumps you to 50/day with longer timeouts.
2. Dead Link Checker API
Crawl any website and find broken links (404s, timeouts, SSL errors).
# Quick single-page check (no browser needed, sub-second)
curl "https://hermesforge.dev/api/deadlinks?url=https://example.com&mode=quick"
# Deep crawl with 50-page limit
curl "https://hermesforge.dev/api/deadlinks?url=https://example.com&max_pages=50"
# CI/CD mode: exit code 1 if broken links exceed threshold
curl "https://hermesforge.dev/api/deadlinks?url=https://example.com&format=github&threshold=0"
What makes it useful: Quick mode checks a single page in under a second without launching a browser. Deep mode crawls entire sites. GitHub Actions format for CI/CD pipelines.
3. SEO Audit API
Get an instant SEO score for any URL — meta tags, headings, images, performance, and more.
curl "https://hermesforge.dev/api/seo?url=https://example.com"
Returns a structured JSON report with scores, issues, and recommendations. Checks title/description length, heading hierarchy, image alt text, Open Graph tags, and more.
4. Tech Stack Detector API
Identify the technologies behind any website — frameworks, CMS, CDN, analytics, and more.
curl "https://hermesforge.dev/api/techstack?url=https://dev.to"
Detects React, Vue, Angular, WordPress, Shopify, Cloudflare, Google Analytics, and dozens more. Useful for competitive research, sales prospecting, or just curiosity.
5. SSL Certificate Checker API
Verify SSL certificates — expiry dates, issuer, chain validity, and security headers.
curl "https://hermesforge.dev/api/ssl?url=https://example.com"
Returns certificate details, days until expiry, and security header analysis (HSTS, CSP, X-Frame-Options). Useful for monitoring certificate renewals across multiple domains.
Why No-Auth APIs Matter
The no-signup model works because:
- Lower friction = more users: Every registration step loses 40-60% of potential users
- AI agents can use them: ChatGPT, Claude, and other AI assistants can call no-auth APIs directly — they can't fill out registration forms
- Script-friendly: Bash scripts, cron jobs, and CI/CD pipelines don't want to manage API keys
- Try-before-you-commit: Developers evaluate APIs by using them, not by reading docs
Rate limiting replaces authentication as the abuse prevention mechanism. You get generous free access; if you need more, create a free API key for higher limits.
Get Started
All 5 APIs (plus 3 more) are available at a single base URL with zero configuration:
https://hermesforge.dev/api/
No signup. No API key. No SDK. Just HTTP.