Question 1

Which regex flavor is this?

Accepted Answer

JavaScript (ECMAScript) regex. That means lookbehind works, backreferences look like \1, and flags are g/i/m/s/u/y. If you're writing regex for Python, Perl, or PCRE, the syntax is close but not identical — named groups and some escape sequences differ.

Question 2

Can I see what each capture group matched?

Accepted Answer

Yes. Every match lists its numbered groups and any named groups with their exact values. Especially useful when you're building something like a URL parser and want to confirm that 'path' captured what you think it did.

Question 3

Does it explain the regex in plain English?

Accepted Answer

Not automatically — it shows you what matches, which in practice is what you need to debug a pattern. For a written breakdown of a complex regex, sites like regex101 offer verbose explanations. This tool is deliberately lighter and faster.

Question 4

Why does my pattern work here but fail in my code?

Accepted Answer

Usually one of three things: your code is using a different regex flavor (Python re, Java Pattern), you're forgetting to escape backslashes when the regex lives inside a string literal, or a flag is missing. Copy the pattern exactly and make sure the flags line up.

Question 5

Is my text sent anywhere?

Accepted Answer

No. The regex runs in your browser against your text — nothing leaves the page. Useful when you're testing patterns against production log excerpts or customer data you shouldn't be uploading.

正規表示式測試器

什麼是正規表示式測試器？

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