# RegEx Knife

> A tool for creating, testing, and editing regular expressions and substitutions. (iPhone/iPad app by Mark Alldritt.)

- Source: https://appshunter.io/ios/app/regex-knife/id894169288 (this page in markdown: same URL + `.md`)
- Developer: [Mark Alldritt](https://appshunter.io/developer/506691275)
- Category: Utilities, Productivity
- Price: Free
- Rating: 4.30/5 from 25 App Store ratings · 26 written reviews indexed
- Age rating: 4+
- Requires: iOS 8.0 · 4 MB
- Languages: American English
- Released: 2014-07-20
- Data updated: 2026-06-11
- Monetization: paid
- User reviews in markdown: https://appshunter.io/ios/app/regex-knife/id894169288/reviews.md

## What is RegEx Knife?

RegEx Knife is an easy and useful tool for working with Regular Expressions.  RegEx Knife is unique in how it allows you to highlight capture groups within a Regular Expression, edit them and immediately see the results.  RegEx Knife also makes it easy to experiment with regular expression substitutions. 

Version 2 retains the simplicity of the original RegEx Knife, with the added advantage that it works on your iPhone as well as your iPad.

## Key features

- Highlight capture groups
- Edit capture groups
- See immediate results
- Experiment with substitutions
- Works on iPhone and iPad

## Recent user reviews (10 of 26)

All indexed reviews: https://appshunter.io/ios/app/regex-knife/id894169288/reviews.md

### 2/5 — Probably needs an update

*2025-07-28, version 2.0.2*

This app has been useful, but recently I can’t exit from a custom RegEx back to the main menu. I’m guessing the app needs to be updated. Otherwise I’d give this a much higher star rating.

### 5/5 — Hands down the best

*2024-11-27, version 2.0.2*

I couldn’t find it in the AppStore sometime ago. Thanks for RegEx Knife.

### 4/5 — Please support Chinese.

*2024-03-24, version 2.0.2*

When there are Chinese characters in the regular expression, they will not be displayed.

### 4/5 — Tool for what?

*2024-03-02, version 2.0.2*

Developer should integrate this into shortcuts where it will actually be useful for different types of extractions and maybe a different more up to date UI

### 4/5 — Works for basic regexes and that’s it

*2022-10-15, version 2.0.2*

It’s nice for simple regexes. Unfortunately, I wanted to use a conditional substitution, but the syntax for that varies by engine and the app doesn’t specify what uses. Would be 5 stars otherwise.

### 2/5 — Unusable in Dark Mode

*2021-12-04, version 2.0.2*

As mentioned in another review nearly a year ago, this app does not work in dark mode. Black on black text is completely unreadable.

### 5/5 — Bug when renaming a new RegEx

*2021-09-25, version 2.0.2*

You fixed the last bug I mentioned and I really like this app layout. 

Found two new bugs.  One is related to dark theme on iPhone.  I can’t see text types in on first type.  It is all black on black.  It fixes itself after a bit of fiddling.

Second is more important.  Creating a new RegEx that takes the untitled name then backing out, rand naming it to String.prototype.string and then it reverted to text from a previous entry.  When opened it showed different regex than the overview page.  It did this a few times until it auto corrected itself.  I have screenshots.  I can’t reproduce this.

These bugs seem to be related to how the app saves on load or on exit?

### 4/5 — Needs a Dark Mode update

*2021-01-20, version 2.0.2*

Excellent tool for fine tuning regular expressions with clear visual feedback.

The custom keyboard keys are equally clever, but turn invisible in Dark Mode. Fortunately it's usable without them.

### 1/5 — Crashes on run.

*2020-07-21, version 2.0.1*

Entered one regex and app crashed. Now the app crashes every time I run it.

### 5/5 — Great app!!!

*2019-11-15, version 2.0.1*

It’s awesome! I wish I would look up simple RegEx documents in the app.

## Frequently asked questions about RegEx Knife

### What does RegEx Knife do?

RegEx Knife is a utility app designed to help users work with regular expressions. It allows you to test, edit, and experiment with regular expressions and their substitutions directly on your device.

### What are the key features of RegEx Knife?

Key features include the ability to highlight and edit capture groups within a regular expression, immediately see the results of your changes, and easily experiment with substitutions. It also supports both iPhone and iPad.

### Is RegEx Knife free to use?

Based on the provided information, RegEx Knife is a paid application. There is no indication of it being free or having in-app purchases or ads.

### What devices is RegEx Knife compatible with?

RegEx Knife is compatible with both iPhone and iPad devices, offering a consistent experience across Apple's mobile platforms.

### Who would benefit from using RegEx Knife?

This app is ideal for developers, programmers, students, and anyone who frequently works with regular expressions for tasks such as data extraction, validation, or text manipulation.

## Version history (last 5 releases)

### 2.0.2 — 2020-09-10

This version introduces Dark Mode support and resolves a number of bugs.

### 2.0.1 — 2019-02-22

This maintenance release addresses a series of iOS 12 compatibility issues and adds support for named regex capture groups (made possible by improvements to the Regular Expression engine included in iOS 11).

### 2.0 — 2017-03-20

RegEx Knife comes to iPhone!  

New Features in RegEx Knife 2.0:

- Runs on all iOS devices from iPhones to the 12" iPad Pro.
- iOS multi-tasking and split-view support.
- Spotlight searching finds expression names and expression content.
- Reorganized UI makes regular expression options more accessible and makes it easier to work with long bodies of sample text.

### 1.0.6 — 2015-10-17

iOS 9 Bug Fixes

### 1.0.5 — 2015-05-04

This release of RegEx Knife corrects a crashing bug that occurs when a Regular Expression contains more than 9 capture groups and when the substitution features are used.

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## More apps by Mark Alldritt

- [Tennis Cards](https://appshunter.io/ios/app/tennis-cards/id1212377801)

All apps by Mark Alldritt: https://appshunter.io/developer/506691275

## Related topics

[regular expression test](https://appshunter.io/ios/topics/regular-expression-test)

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*Data collected daily from the US App Store and indexed by [AppsHunter](https://appshunter.io/). User reviews are verbatim App Store reviews. Ratings, prices and chart positions refresh continuously; this snapshot is from 2026-06-11.*