About this studio

Pikkola, tool No. 13

A regex tester should answer in the time it takes to type a pattern.

Why another one

Most testers we used were either a documentation page with a small box at the top, or a full application that wanted an account and loaded a framework before it could highlight a word. This is one page with two boxes and a table.

Which engine runs

The browser's own JavaScript RegExp, the same one that runs in Node. A pattern that works here works there. The code panel says where the other engines differ, because they do: Go and the Rust regex crate have no backreferences, and their named group syntax is not the same.

The presets

Each preset is a pattern we ran against its own sample and against a line it should not match. The Korean patterns are the ones we use: a mobile number with the 010 prefix required, and the business registration number with its check digit left to the reader. A preset with a country is labelled with that country, since a phone number is not a universal thing.

What it will not do

It will not run your pattern on a server, and it will not protect you from a pattern that backtracks for a minute. It stops after ten thousand matches and says so, and it shows how long the match took. That is a warning, not a guarantee.

If something is wrong

Write to hello@pikkola.com with the pattern, the flags and the text. For this tool that is the whole bug report.