Guides & tutorials
Practical, example-driven guides to the FreeTools APIs. Every example runs as-is — no keys, no signup.
Use these guides when you need a working example rather than a tool tour. They cover the FreeTools REST endpoints and the practical decisions around them: what a response means, how to avoid rate limits, and how to keep a browser or CI job safe. Every example uses the public production URLs, so you can copy it directly into a terminal or an application.
New here? Start with the LOC guide or star history guide for repository data; use the headers checklist and SSRF guide when you are building or auditing an API that accepts URLs.
Browse the guides
- How to Check TLS Certificate Expiry with a Free API — inspect the protocol, cipher and remaining certificate lifetime, then automate the check.
- Count Lines of Code in a GitHub Repository with a Free API — count public GitHub or GitLab repositories by language, with optional file-level detail.
- Free CORS Proxy for Developers: Bypass Cross-Origin Errors Safely — understand preflight requests and use a guarded proxy while debugging browser calls.
- Free Developer Tools for Open Source Maintainers (No Signup) — a practical roundup for repository analysis, growth tracking and domain health.
- Free IP Geolocation API With No Key (2026 Guide) — resolve IPv4, IPv6 and hostnames to location data in JSON or XML.
- Free Weather API With No API Key (City or IP Lookup) — fetch current conditions by city or caller IP without creating an account.
- GitHub API Rate Limits: 5000 Requests an Hour, Explained — use ETags, conditional requests and stale-while-revalidate to avoid wasted quota.
- GitHub Star History API: Chart Repo Growth for Free — compare repositories and embed a live SVG chart in a README.
- HTTP Security Headers Checklist: CSP, HSTS and CORS (2026) — check the response headers that prevent common web attacks.
- README Badges and Widgets for Your GitHub Repository — keep live charts and counters current without a build step.
- SSRF Prevention for APIs: Block Server-Side Request Forgery — validate DNS results and every redirect hop in URL-fetching services.