# Tool to visualize (and explain) regular expressions?
**URL:** https://community.mp3tag.de/t/tool-to-visualize-and-explain-regular-expressions/62328
**Category:** Support
**Created:** [October 8, 2023, 11:21am UTC](https://community.mp3tag.de/t/tool-to-visualize-and-explain-regular-expressions/62328 "2023-10-08T11:21:17Z")
**Posts on this page:** 8
**Page:** 1
### Author:  [@Casual\_Tea](https://community.mp3tag.de/u/Casual_Tea)
#### Post date: [October 8, 2023, 11:21am UTC](https://community.mp3tag.de/t/tool-to-visualize-and-explain-regular-expressions/62328/1 "2023-10-08T11:21:17Z")
> [@Regex not working in specific situation for (Featuring)](https://community.mp3tag.de/t/regex-not-working-in-specific-situation-for-featuring/62307/2):
>
> This one is for some derivates of "featuring" **if it is has a leading space**.
Out of curiosity, did you make that visualization yourself or are you using a tool I'm not aware of? Looks really neat to quickly understand a more complicated regex.
---
### Author:  [@LyricsLover](https://community.mp3tag.de/u/LyricsLover)
#### Post date: [October 8, 2023, 11:33am UTC](https://community.mp3tag.de/t/tool-to-visualize-and-explain-regular-expressions/62328/2 "2023-10-08T11:33:34Z")
I use this free online visualization tool:
> **[Regexper](https://regexper.com/)**
>
> Regular expression visualizer using railroad diagrams
Sometimes, some very special syntax like the `(?i)` in the above regex (to make the regex match case **IN** sensitive) does not work in the visualization tool and you get an error:
Then you have to adjust the expression accordingly.
**UPDATE** :
See the extended Regexper clone in this [later added answer](https://community.mp3tag.de/t/tool-to-visualize-and-explain-regular-expressions/62328/7).
---
### Author:  [@Casual\_Tea](https://community.mp3tag.de/u/Casual_Tea)
#### Post date: [October 8, 2023, 11:54am UTC](https://community.mp3tag.de/t/tool-to-visualize-and-explain-regular-expressions/62328/3 "2023-10-08T11:54:13Z")
As it happens the first of my expressions that I tested already revealed a few oversights on my part.
I fell for the classic `.` vs `\.` mistake.
This is supposed to match `album [bit depth/KHz/channels]` or `album [bit depth-KHz-channels]`, for example `Chicago II (Steven Wilson Remix) [24/96/5.1]`.
That visualization quickly enabled me to fine-tune my regex to:
Thanks a lot for the tool! 🙂
---
### Author:  [@LyricsLover](https://community.mp3tag.de/u/LyricsLover)
#### Post date: [October 8, 2023, 12:12pm UTC](https://community.mp3tag.de/t/tool-to-visualize-and-explain-regular-expressions/62328/4 "2023-10-08T12:12:10Z")
Just a little detail:
`\d{2,3}`
is visualized by Regexper with
This can be a little bit confusing, because it means, that the search for a digit will be (additionally!) repeated 1 or 2 times. This leads to a number with 2 or 3 digits (from 00 to 999).
Other tools visualize it as
It's a matter of taste which one you like better. 😉
---
### Author:  [@Casual\_Tea](https://community.mp3tag.de/u/Casual_Tea)
#### Post date: [October 8, 2023, 12:18pm UTC](https://community.mp3tag.de/t/tool-to-visualize-and-explain-regular-expressions/62328/5 "2023-10-08T12:18:41Z")
> [@LyricsLover](#):
>
> This can be a little bit confusing, because it means, that the search for a digit will be (additionally!) repeated 1 or 2 times.
I noticed that and found it a bit odd.
Thinking about that lead to the change in my regex tho as I previously had `\d+` there. However for KHz the only possible values (for my data set) are 44.1, 48, 88.2, 96 and 192.
So while I agree that the visualization of that part can be confusing I did intend to use `\d{2,3}` with the optional matching of the dot and another digit.
---
### Author:  [@LyricsLover](https://community.mp3tag.de/u/LyricsLover)
#### Post date: [October 9, 2023, 7:50am UTC](https://community.mp3tag.de/t/tool-to-visualize-and-explain-regular-expressions/62328/6 "2023-10-09T07:50:15Z")
In the [official documentation](https://regexper.com/documentation.html) of Regexper I found this explanation for the quantifier:
Greedy on the left side:`\d{5,10}`
Non-greedy on the right side: `\d{5,10}?`
> The ranged quantifier specifies a number of times the pattern may be repeated. The two examples provided here both have a range of "{5,10}", the label for the looping branch indicates the number of times that branch may be followed. **The values are one less than specified in the expression since the pattern would have to be matched once before repeating it is an option**. So, for these examples, the pattern would be matched once and then the loop would be followed 4 to 9 times, for a total of 5 to 10 matches of the pattern.
BTW: If you hover upon the label "4...9 times", you see:
---
### Author:  [@LyricsLover](https://community.mp3tag.de/u/LyricsLover)
#### Post date: [October 9, 2023, 9:04am UTC](https://community.mp3tag.de/t/tool-to-visualize-and-explain-regular-expressions/62328/7 "2023-10-09T09:04:34Z")
And for those looking for an extended Regexper site that also handles the mentioned `(?i)` flag
and some other specialities like
named capture groups `^\d(?[a-zA-Z])$`
or
positive lookbehind assertions `(?<=([abc]))`
or
negative lookbehind assertions `(? **[Regexper](https://uzitech.github.io/regexper/)**
>
> Regular expression visualizer using railroad diagrams
Source Code [on Github](https://github.com/UziTech/regexper/)
Just switch to the `PHP` flavour to see the extended possibilities:
---
### Author:  [@system](https://community.mp3tag.de/u/system)
#### Post date: [November 8, 2023, 9:05am UTC](https://community.mp3tag.de/t/tool-to-visualize-and-explain-regular-expressions/62328/8 "2023-11-08T09:05:27Z")
This topic was automatically closed 30 days after the last reply. New replies are no longer allowed.