About Dev Tools !
A privacy-first, open-source suite of developer utilities built with love by Cosyslabs.
Our Mission
Developers shouldn't have to choose between convenience and privacy. Too many online tools send your sensitive data — JWTs, passwords, hashes, source code — to servers you don't control.
Dev Tools ! runs 100% in your browser. No server round-trips for tool processing. No tracking of your inputs. No paywalls for core features.
Open Source Philosophy
We believe developer tools should be transparent and auditable. Dev Tools ! is fully open source under the MIT licence. You can inspect the code, fork it, self-host it, or contribute new tools.
⭐ View on GitHub →Tech Stack
About Cosyslabs
Cosyslabs is an independent software studio focused on building useful, privacy-respecting tools for developers. We're a small team with a big belief: software should serve its users, not the other way around.
Visit cosyslabs.com to learn more about our studio and the people behind it.
Part of the Cosyslabs Family
Dev Tools ! is one of 20 sites built by Cosyslabs. They share the same approach: the work happens in your browser, the tools are free, and nothing asks you to sign up first.
Closest to this one
- Convert All! — Unit, data-size, currency and timezone converters
- PDF Convert All! — PDF conversion, merging and compression, in the browser
- Routine Toolkit — 160+ everyday calculators and productivity tools
- CastFleet — AI content and marketing platform for solo founders
- Astrilio — Property management software, with a public API and MCP server
- Learn Pass Grow — Grade calculators, practice tests and certification paths
If you freelance or run your own thing
- BizPhoton — Break-even, pricing, employer-cost and LLC-cost calculators
- Work, Money & Tax — Contractor and 1099 tax estimators, severance and paycheck math
- Budget Build Invest — Personal finance calculators for the US, Canada, UK, India and Australia
- Instant Template Hub — Printable invoices, planners and resume templates
The rest of the family
- Rough Estimator — Construction and material cost estimators
- Debt & Bills — Debt payoff planning and medical-bill negotiation tools
- Gov Money Benefits — Federal employee, VA disability, SSDI and military pay calculators
- Legal by the Numbers — Child support, settlement and property-tax calculators by state
- The Wise Senior — Medicare cost and Social Security claiming education
- My Health My Wellness — Health and fitness calculators, each cited to a primary source
- The Ballast Principle — Stress, sleep and focus tools, and the book they come from
- Recipes and Measures — Kitchen math: scaling, substitutions and conversions
- Kids Color Works — Printable coloring pages, worksheets and tracing sheets