Frequently Asked Questions
Is there an offline app for regex101?
The website utilizes service workers under the hood, which means, if your browser supports them it will run offline. Nothing is stored or required from the server (after the initial load has been made) which means it can run offline without any hiccups.
How to prefill the fields on the interface via URL?
For most of the cases, you should be using permalinks instead. This can be done through the UI or the API.
If this still does not suit you, you can prefill the fields using query parameters like so:
https://regex101.com/?regex=<regex>&testString=<text>&flags=<flags>&subst=<replacement>&delimiter=<delimiter>
Reference Chart
| Parameter | Example |
|---|---|
| regex | .* |
| testString | Lorem Ipsum |
| flags | is |
| subst | Dolor Sit Amet |
| delimiter | @ |
The content of any permalink will override the query parameters
How to get / link the latest version of a regex URL or entry?
Append /latest to a regex link rather than the version number. For example: https://regex101.com/r/JvLFcG/latest
How close does regex101 emulate or match the regex engines?
See the flavor guide in the application.
Why is regex101's result different from PHP's for regex specifying non-ASCII character without u flag?
It's mainly because regex101 is compiled from PCRE 16-bit library, while PHP uses PCRE 8-bit library. This means that in default mode, the regex and the input are treated as an array of UTF-16 code units on regex101, instead of an array of bytes in PHP.
Unless you are working with binary content, always turn on UTF mode with u flag to interpret both the regex and the input string as an array of Unicode characters.
Is there a limit on the size of the input fields?
On client side, regex101 doesn't impose any limit. You are only limited by your browser and the processing power of your machine.
When you save your regex as permalinks, there are limits imposed by the database. If you exceed those limits, your request will be rejected by the API.
Is there live help available?
Feel free to drop in the IRC channel or Discord.
Will you open source Regex101?
No.