Regex Tester & Validator

This regex matches 1 to 4 space-separated CSS length values, making it ideal for properties like border-width, margin, or padding. Each value can be 0 or a number (including decimals and optional +/- signs) followed by a CSS unit such as px, em, rem, %, or viewport units. It validates the full line, allowing leading/trailing whitespace. The global and multiline flags enable matching multiple lines of input at once.