Regex Explainer

Break down any regular expression into plain English descriptions.

freeworks offlinenothing uploaded
Input
Output
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About regex explainer

Regex Explainer does its work in front of you rather than sending anything away to be processed. What you see is the whole of it.

Paste a customer record into it if you need to. The record never leaves the machine you are sitting at.

You will find it under Regular expressions, alongside 18 other tools for the same sort of job.

Explains character classes, quantifiers, groups, anchors, and lookaheads.

How to use it

01
Start it
Every control is on the tool itself. Keyboard shortcuts, where there are any, are listed beside it.
02
Watch it run
It updates in the page as you go. Nothing is sent anywhere, so it keeps working with the network off.
03
Close when done
Nothing is stored between visits. Reloading gives you a clean start rather than picking up where you left off.

Examples

Explain email validation regex in plain English
Get a plain English explanation of an email validation regex
Input
^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$
Output
Pattern: /^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$/

This regex matches: at the start of the string, then any character in [a-zA-Z0-9._%+-], then repeated one or more times, then the character '@', then any character in [a-zA-Z0-9.-], then repeated one or more times, then the literal character '.', then any character in [a-zA-Z], then repeated 2 or more times, then at the end of the string

Questions

Does Regex Explainer work offline?+

Yes. It is JavaScript running in this tab, so once the page has loaded it needs nothing further from the network. Put the machine in flight mode and it carries on. Nothing you do here is sent anywhere, because there is nowhere for it to go.

Does it remember anything between visits?+

No. Reload the page and it starts from nothing. There is no account, no saved state and no cookie holding your last session. That is a deliberate trade: it cannot lose your data because it never keeps any.

Is it accurate?+

Timing comes from performance.now(), the high resolution clock the browser provides, rather than from setInterval, which drifts by a few milliseconds every tick and compounds over minutes. What can still shift things is the browser throttling a tab in the background, so leave it visible if the timing matters.

Does it make a sound?+

Where a sound makes sense, it is generated with the Web Audio API rather than loaded as a file, so there is nothing to download and nothing to block. Browsers refuse to start audio until you have interacted with the page, which is why the first press is what switches it on.

Can I use Regex Explainer on a phone?+

Yes. The controls are sized for touch and the layout collapses to one column on a narrow screen. Bear in mind that a phone locking its screen will suspend the page, and timing stops with it.