Free online developer tools — fast & private

Flashman has 28 tools. Browse developer utilities for JSON, JWT, encoding, hashing, cron, Markdown, and MATLAB/Simulink workflows—processed locally in your browser. No signup, no uploads.

• ✓ 100% client-side
• ✓ No account needed
• ✓ Free forever

Start here

New to a topic? These guides explain the concepts and link to the tools.

• Portainer stack environment variables: a safe deploy guide
• Markdown writing guide: syntax, preview, and export
• JSON formatting and validation: a practical guide
• JWT explained: how to decode tokens safely

From the blog

Workflows, debugging tips, and product updates.

• UUID v7 time-order debugging
• CSS @scope proximity debugging
• Partitioned cookie CHIPS debugging
• Cron @daily and @reboot debugging
• WCAG contrast from painted colors
• PostgreSQL statement, lock, and idle timeout debugging

Who runs Flashman

Flashman is a free site of browser-based developer utilities, written guides, and debugging notes. Rahul Chitturi operates it. Formatters, encoders, and converters run on your device. Pasting a token or a config here is not an upload.

Hosting is funded in part by advertising. Google AdSense can show an ad only after you choose Accept on the cookie banner. Reject leaves analytics and advertising storage off. The privacy policy explains the cookies, how to change your choice, and how to reach the operator.