Converter

Two colours, seen four other ways — because the failure is not that a design looks worse, it is that two meanings become one colour.

Convert between hex, RGB and HSL, and check whether two colours are readable together.

A full shade scale from one colour, with the text colour that actually passes contrast on each step.

Build a gradient, see it full width, and copy the declaration — with stop positions left to CSS unless you set them.

Convert configuration to YAML with the strings that would change meaning quoted — including the country code that loads as false.

Convert between binary, octal, decimal, hexadecimal and any base up to 36 — exactly, at any size.

Amounts written out the way an invoice or a cheque needs them, in English or Vietnamese.

Numbers to Roman numerals and back, with strict reading — IIII and IM are told apart from IV and CMXCIX rather than quietly added up.

Convert a Unix timestamp to a date, or a date to a timestamp — in UTC and your own zone.

See one moment across several places at once — with the hours that do not exist called out.

Convert length, weight, temperature, data, area, volume, speed and time.

Reads the YAML that appears in real config files, and says when it meets syntax it will not guess at rather than quietly mis-reading it.