Free · See likely output lengths

Regex Sample Length Explorer

Generate a test batch and compare its shortest, longest, and average string lengths.

Real randexp.js generation
Private in your browser
Safe count and repeat caps

Explore sample lengths

Enter a pattern without / slash marks. Samples are generated locally with safe count and repeat caps.

Set the pattern13 / 400 characters

Regular expressionWrite the pattern only. Example: ^[A-Z]{3}-\d{4}$

FlagsOptional. Use each flag once.Number of samples1 to 250Open repeat capCaps * and + from 1 to 40.Seed (optional)The same seed repeats the set.

Private local generatorrandexp.js 0.5.3 · no upload

Use the samplesReady when you are

Your samples will appear here

Nothing is uploaded. A safety cap keeps open-ended repeats and large batches under control.

Three simple steps

How to use it

Enter the regular expression.
Generate a varied sample batch.
Review the length range and simple histogram.

Your pattern stays on this device

randexp.js makes every string inside this browser tab. Bookify does not upload or save the pattern, seed, or samples. Generation is capped, and random examples do not replace full validation tests.