Convert between seconds, milliseconds, and date.

Batch generate UUID v4 (crypto.randomUUID).

Time-sortable unique ID, batch generate.

Short random string with customizable alphabet.

px/rem and byte KiB/MB conversions.

Character reference for codes 0–127.

Mod 97 check digit validation.

Bank card number mod-10 validation.

Parse and format to E.164 (libphonenumber-js).

Phonetic alphabet, Morse code, and six-dot Braille.

CODE128/EAN and other 1D barcodes (JsBarcode).

Browser-side transcoding via ffmpeg.wasm (CDN core).

TOTP two-factor authentication code generator.

Generate Authorization header from username and password.

Parse HTTP Cookie header string into table.

Generate/edit JWT with custom header, payload, and secret.

Generate SVG placeholder images with custom dimensions and colors.

Online stopwatch: start/pause/reset/lap.

Add/subtract days, calculate date intervals.

Percentage calculations.

Convert between °C, °F, K temperature units.

Convert between Arabic and Roman numerals.

Look up vendor by MAC prefix (OUI).

Calculate CIDR notation from IP range.

Common port numbers and protocols reference.

Evaluate math expressions with functions and constants.

Estimate remaining time from progress and elapsed time.

Generate random MAC addresses with prefix and case options.

Detect browser, screen, network and system information.

Estimate token count for GPT-4/GPT-3.5/Claude models.

Calculate simplest ratio and reverse compute from known side.

Equal installment / equal principal with payment schedule.

Calculate BMI value and category with reference chart.

Calculate work duration, overtime, and salary estimate.