Test Regex Without Sending Your Data to a Server
2 min readZeroKit Team
Test regular expressions in real-time without sending data to a server. Free regex tester with match highlighting, groups, and common patterns.
Regular expressions are powerful and easy to get wrong. You tweak a pattern, re-run a test, repeat — often dozens of times. Online testers help, but your test corpus may include real customer emails, log lines, or production JSON.
The risk of upload-based testers
Some popular regex playgrounds transmit both pattern and subject to a remote service. That is convenient for sharing links — risky for sensitive strings.
ZeroKit's regex tester runs JavaScript RegExp locally. Your pattern and haystack stay in-tab.
Test privately → ZeroKit Regex Tester
What you get
- Live matching as you edit (depending on tool UX)
- Flags such as
g,i,m,swhere exposed in the UI - Group capture visibility for debugging
- A curated list of starter patterns for email, URLs, hex colours, etc.
Regex cheat sheet
| Token | Meaning |
|---|---|
. | Any char (except newline by default) |
\d | Digit |
\w | Word char |
\s | Whitespace |
^ / $ | Start / end |
[abc] | Character class |
(a|b) | Alternation |
(group) | Capturing group |
{n,m} | Repetition bounds |
Example patterns
| Use case | Starting point |
|---|---|
| Email (simple) | [a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,} |
| IPv4 (loose) | \b\d{1,3}(\.\d{1,3}){3}\b |
| Hex colour | # + 3- or 6-digit hex (build in regex tester) |
Want English → regex? Try the AI Regex Builder.
FAQ
Which regex flavour?
The tool uses JavaScript regular expressions — good for browser and Node stacks, not identical to PCRE or every engine.
Production tip
Always re-test critical patterns in the runtime that will execute them (Java, Go, Python, etc.) — edge cases differ.