CapyToolkit

CapyToolkit is a growing collection of free, privacy-first browser tools. It started the way a lot of side projects do: a solo developer got tired of online utilities that demand an account, an upload, or an email address before doing ten seconds of work. So every one of its 50+ tools runs in the browser, and nothing you touch reaches a server.

The catalog is deliberately practical. Hardware testers cover gamepad stick drift, mouse polling rate, dead pixels, webcam lighting, and microphone noise floor and latency. Developer and security tools cover JWTs, JSON, and photo metadata. Personal tools handle passport photos, image file-size limits, PDFs, phone-scanned documents, and receipt splitting. Nine categories in all: hardware, developer, security, audio, math, text, design, network, and personal.

It runs as a website, an installable PWA, or a Windows app from the Microsoft Store, and works offline once installed. Always free, no account, and new tools ship regularly.