I built HeaderLab — an open-source web security toolkit that runs entirely in your browser

📰 Dev.to · Kadir Buyukguclu

Learn about HeaderLab, an open-source web security toolkit that runs in your browser, and its four client-side tools for HTTP headers and security checks

intermediate Published 30 Jun 2026

Action Steps

Run HeaderLab in your browser to test its four tools
Use the HTTP headers checker to identify missing or misconfigured headers
Configure and test a Content Security Policy (CSP) using the CSP builder and evaluator
Decode and verify JSON Web Tokens (JWT) using the JWT decoder and verifier

Who Needs to Know This

Web developers and security professionals can benefit from using HeaderLab to identify and fix security vulnerabilities in their web applications

Key Insight

💡 HeaderLab provides a convenient and accessible way to perform web security checks and tests directly in the browser

Key Takeaways

Learn about HeaderLab, an open-source web security toolkit that runs in your browser, and its four client-side tools for HTTP headers and security checks

Full Article

Four tools (HTTP headers checker, CSP builder, CSP evaluator, JWT decoder + verifier), all client-side. Here's what I built and the architectural decisions behind it.

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