Everything in the catalog

Generates random UUIDs.

Generates random UUID v4 values with options for hyphens and uppercase.

Checks two colours against the WCAG AA and AAA contrast ratios.

Converts images to WebP in batches with a quality control.

Converts XML into JSON.

Converts YAML into JSON.

Collection of color tools including a gamut mapper, contrast checker and color-space converter.

Single-page bingo game with emoji instead of numbers.

Polish B2B net income calculator comparing ryczalt, flat-tax and tax-scale options (Polish).

Open-source generator and metronome for studying polyrhythms with multiple simultaneous beat patterns.

Tries JSONata query and transformation expressions against sample JSON.

Spider solitaire card game playable in the browser.

Frontend app for creating 5e style monster stat blocks that look like the official ones.

Analyzes more than a dozen fingerprinting signals your browser exposes and summarizes the privacy risks.

Computes Ghana take-home pay, income tax and SSNIT contribution from gross income.

Offline-first invoice maker with multiple company headers, history and PDF export; data stays on your device.

Browser viewer for molecular structures that loads PDB, SDF and other files.

Builds a matrix of which colour pairs in a palette meet accessibility contrast.

Compiles modern JavaScript with Babel presets and plugins in the browser and shows the output.

Estimates how long a circuit runs on a chosen battery type from its capacity and the load.

Demo page for a JavaScript barcode writer supporting many barcode types.

Suggests nearby colours that meet the WCAG contrast requirement.

Converts CSS declarations into a JavaScript style object for CSS-in-JS libraries.

Maps plain CSS rules onto equivalent Tailwind utility classes.