The “quick conversions” of development, for free. In your browser alone.

Over 40 free developer tools that work entirely in your browser

Dev Tools is a free collection of the “quick conversions” developers reach for every day — Base64, URL and HTML entity encoding/decoding, formatting and validating JSON, XML and SQL, converting JSON to YAML or TypeScript types, Markdown preview and diff comparison, and generating UUIDs, hashes, passwords, JWTs, cron expressions and favicons — all completed in your web browser. No account and no software installation required: just open the tool you need, type your input, and start working right away.

Alongside design helpers such as gradient, box-shadow, flexbox and grid CSS generators and a WCAG contrast checker, it also includes tools that come up constantly in Japanese development work, such as Japanese era to Gregorian year conversion and full-width to half-width character conversion. From inspecting a JWT payload to working out chmod values and looking up HTTP status codes, you can clear the small daily jobs all in one place.

Because every operation runs inside your browser (client-side), the text and files you enter are never uploaded to a server. Generated values and files can be copied or downloaded straight to your device, and closing the page clears them from your browser’s memory as well. No sign-up and no uploads — use it with confidence.