New: 90 free tools for developers
By Flavio Copes
I launched a new tools section on the site: 90 free calculators and utilities for developers, running entirely in your browser. No signup, no ads.
I just launched a new section on this site: flaviocopes.com/tools.
It’s a collection of 90 free tools for developers. Calculators, utilities, little helpers for things I kept doing by hand or with random sites full of ads. It has since grown to 222 tools.
Why build them? To be useful. I’ve been writing tutorials for years to help people learn. Tools are the same idea in a different shape: instead of explaining something, I give you something you can use right away.
A few principles I followed:
- Free, no signup. Open the page, use the tool, done.
- Everything runs in your browser. Your data never leaves your machine. Paste a JWT in the decoder or a prompt in the token counter, and nothing gets sent to a server.
- No ads, no tracking, no dark patterns.
The tools are grouped by category. For AI and LLMs, there is an inference cost calculator to estimate your monthly LLM bill. The token counter shows what a prompt costs on every major model. I also added a subscription vs API break-even calculator, a context window fit checker, and an AI agent cost visualizer that shows why multi-step agent runs get expensive.
The JavaScript and TypeScript section includes a regex tester with a plain-English explainer, JSON formatter, JWT decoder, and JSON to TypeScript converter. There’s also an event loop visualizer that steps through microtasks vs macrotasks.
For CSS and HTML, you can use the flexbox playground or paint named areas in the CSS grid generator. The section also has a color converter with WCAG contrast checking and a clamp() calculator for fluid typography.
The Git tools solve two common problems. A command finder turns your goal into a command, while the “Git oh no” recovery tool helps when things go wrong.
For databases, I added a database chooser, SQL formatter, and SQL to Prisma to Drizzle schema converter.
The web platform section has a CORS debugger, Cache-Control header builder, and timestamp converter. The cron expression builder includes a preview of the next run.
There are business and writing tools too, including a freelance rate calculator, SaaS MRR calculator, and payment platform fee comparison for Paddle, Stripe, Gumroad, Polar, and Lemon Squeezy.
And a lot more: the full list is on the tools page, organized by category.
One small exception to the “browser only” rule: the app idea generator has an optional AI mode that calls a small model on the server. It’s rate limited so it stays free, and the curated ideas work without it.
If there’s a tool you’d love to have, let me know. If it’s useful to you, it’s probably useful to a lot of people.
Check them out at flaviocopes.com/tools.
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