CapyToolkit is a free reference library that also works as a toolbox: 45+ browser utilities, each paired with the reference content that explains it.
The catalog spans nine categories. Hardware and display diagnostics cover screens, gamepads, keyboards, and input lag. Developer parsers and encoders handle formats and conversions. Security and privacy tools scrub metadata and check exposure. Audio and acoustic testing includes speaker sweeps, microphone tests, and tone generators. Math and engineering calculators cover resistors and subnet math. Text analysis and web design utilities include colour conversion and contrast checks, while network references make MIME types and HTTP status codes searchable. Personal tools cover passport photos, PDFs, phone scans, image size limits, and receipt splitting.
Every tool page adds worked examples: the resistor calculator explains band tolerance, the subnet calculator breaks down CIDR notation, and the contrast checker quotes WCAG AA and AAA thresholds. A blog supplies hands-on guides and buying advice on the same topics.
Everything runs client-side in the browser. Files never upload, text never leaves the tab, and no account is required. The site installs as an app, works offline, and is also on the Microsoft Store for Windows. New tools ship regularly.
