Regex101 alternative: a simple, private regex tester
Regex101 is the go-to regex playground for good reason. It explains each token, supports several regex flavours and lets you save and share patterns. If you write regular expressions often, it is hard to beat.
A lighter alternative helps in narrower situations. Maybe you only need to check a JavaScript pattern against a sample string, or the sample text contains real data you would rather not paste into a website. MergeDoc's Regex Tester uses your browser's own JavaScript RegExp engine and highlights matches as you type.
That means it tests exactly what your JavaScript will do, and nothing more.
Why people look for a Regex101 alternative
Real data in your test string
Testing a pattern against log lines or customer records means pasting them somewhere. A local tester keeps that text on your machine.
You only need JavaScript
Multi-flavour playgrounds are valuable, but if your code runs in a browser or Node, the native engine is the one that matters.
Less to learn for a quick check
A pattern box, a flags box and a text area cover most one-off checks. If you are new to regex, how to test a regex walks through it.
Checking a pattern before shipping
A regex that looks right can still match too much. Running it against a few realistic strings, including awkward edge cases, catches mistakes before they reach production code or a validation form.
Learning by trying
Seeing matches highlight as you type is one of the fastest ways to learn how quantifiers, anchors and character classes behave. A small, uncluttered page keeps the focus on the pattern itself.
Regex101 vs MergeDoc, side by side
| Regex101 | MergeDoc | |
|---|---|---|
| Where your text goes | Patterns and test strings are processed by their service; saving creates a stored copy. | Matched in your browser with the native RegExp engine. Nothing is stored. |
| Sign-up | Testing typically works without an account; saving and library features may use one. | None. |
| Usage limits | Check their current terms. | None from us. |
| Watermark / ads | Free site is typically ad-supported. | No watermark. The site may show ads. |
| Regex flavours | Supports several engines, such as PCRE, Python, Go and Java, in addition to JavaScript. | JavaScript only, because it uses your browser's engine. |
| Explanations | Token-by-token explanation of the pattern and a debugger. | None. You see highlighted matches and an error if the pattern is invalid. |
| Offline use | Needs a connection. | Works after the page has loaded. |
| Sharing | Permalinks and a community library of patterns. | No sharing or saving. |
When Regex101 is still the better pick
- •You write regex for Python, PHP, Go, Java or another non-JavaScript engine and need flavour-accurate results.
- •You want a plain-English explanation of what each part of the pattern does.
- •You want to save patterns, share permalinks or browse a library of community examples.
- •You need a step-by-step debugger to understand catastrophic backtracking.
- •You are debugging a slow pattern and want to see how many steps the engine takes before it matches or fails.
- •You need to generate code snippets or a substitution preview directly from the pattern.
- •You want a quick reference panel beside the editor listing tokens, anchors and quantifiers while you write.
- •You need to test multi-line inputs against engine-specific modes that JavaScript does not offer, such as inline flags or possessive quantifiers.
How to switch in a few steps
- 1.
Open Regex Tester and type your pattern.
- 2.
Set flags if you need more than the default g, then paste your sample text.
- 3.
Matches highlight live. If the pattern is invalid, an error shows instead, so you can adjust and retry.
Tools covered
Read next
How to Test a Regex Online Before You Ship It
A regex that looks right can still match too much, too little, or hang. Test it against real inputs in your browser before it reaches production.
Why Client-Side Tools Matter: Keep Files on Your Device
Most online file tools upload your data to a server. Here is why many tasks do not need that, and the honest trade-offs of doing it locally.
Why Minified JSON Is Hard to Debug (and How to Fix It)
Minified JSON is great for machines and painful for people. Learn to format, validate and minify JSON, and spot the usual syntax errors fast.
Other alternatives
Frequently asked questions
- Is there a simple Regex101 alternative with no account?
- Yes. MergeDoc's Regex Tester needs no account and does not store your patterns or text.
- Which regex flavour does it use?
- JavaScript, via your browser's built-in RegExp. Patterns for other engines may behave differently.
- Does it explain my pattern?
- No. For explanations, use a dedicated explainer or read [how to test a regex](/blog/how-to-test-a-regex).
- What flags are supported?
- Any flags your browser's RegExp accepts, such as g, i, m, s and u. The flags box defaults to g.
- Does it show capture groups?
- It highlights each full match. It does not list capture groups separately.
- Is my test text uploaded?
- No. Matching runs entirely in your browser.
- Why does my pattern behave differently in Python?
- Regex flavours differ in features such as lookbehind, named groups and Unicode handling. This tester uses JavaScript, so confirm the result in your target language.
Regex101 is a trademark of its owner and is named here only for comparison. MergeDoc is not affiliated with or endorsed by Regex101. Check their current terms for the latest details.