Built by Developers, for Developers
OneDev Tools is a free, open collection of developer utilities — JSON formatters, token counters, hash generators, regex testers, and 150+ more tools — designed around one simple principle: your data never leaves your device.
Why We Built This
Most online developer tools quietly upload your data to a server, run analytics on your usage, or gate basic features behind a login. When you paste an API key into a Base64 decoder, you probably don't expect it to be logged — but with many tools, it is.
OneDev Tools was started in 2024 out of frustration with exactly this. We wanted a single reliable resource for the everyday utilities developers actually need — JSON formatting, token estimation, hash generation, regex testing — without the privacy tradeoffs.
Every tool on this site runs entirely in your browser. No data is sent to our servers. No accounts required. No paywalls.
What's Inside
AI & LLM Utilities
Token counters, cost estimators, context window planners, and embedding calculators for GPT-4o, Claude, Gemini, and more.
JSON Tools
Format, validate, diff, convert, and visually explore JSON structures with our suite of 8 JSON utilities.
Security Tools
CSP generators, CORS builders, password testers, JWT decoders, hash generators, and security header references.
Git Tools
Gitignore generators, commit formatters, branch name builders, diff viewers, and README generators.
CSS Generators
Visual builders for gradients, box shadows, animations, flexbox, grid, and CSS layout utilities.
Converters
Unit converters for CSS, length, data size, time, color, typography, number base, and screen resolution.
Text Tools
Case converters, diff checkers, regex testers, word counters, line sorters, and lorem ipsum generators.
Image Tools
Browser-side image compression, resizing, cropping, format conversion, and EXIF metadata viewer.
🔐 Our Privacy Commitment
- ✓ All tool processing happens locally in your browser — nothing is sent to a server.
- ✓ We do not store, log, or analyze any text you paste into any tool.
- ✓ No account creation required. We don't collect email addresses.
- ✓ We use Google AdSense for revenue, which may set cookies for ad personalization. See our Privacy Policy for details.
How It's Built
OneDev Tools is built with SvelteKit and deployed on Cloudflare's edge network for fast global access. The UI is styled with DaisyUI and Tailwind CSS. All tool logic runs client-side using standard browser APIs and JavaScript — no backend servers process your data.
Accuracy & Updates
We maintain accuracy across all tools through regular reviews, particularly for data that changes frequently — such as AI model pricing. The AI model pricing data is updated at minimum monthly as providers update their APIs. If you notice outdated information or a bug, please contact us and we'll correct it promptly.