# Changing File extensions
**URL:** https://community.mp3tag.de/t/changing-file-extensions/6103
**Category:** Support
**Created:** [January 20, 2008, 11:51am UTC](https://community.mp3tag.de/t/changing-file-extensions/6103 "2008-01-20T11:51:25Z")
**Posts on this page:** 4
**Page:** 1
### Author:  [@shroppie](https://community.mp3tag.de/u/shroppie)
#### Post date: [January 20, 2008, 11:51am UTC](https://community.mp3tag.de/t/changing-file-extensions/6103/1 "2008-01-20T11:51:25Z")
In order for the IPOD to recognise Audio Books properly i.e. as a book and not as music. It first has to be converted to MP4 format, using Itunes, giving the file an m4a extension, this is then converted by hand to m4b. I have around 1,200 file to convert. Is there anyway MP3TAG can do the simple change from a to b in the extension ?
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### Author:  [@dano](https://community.mp3tag.de/u/dano)
#### Post date: [January 20, 2008, 9:30pm UTC](https://community.mp3tag.de/t/changing-file-extensions/6103/2 "2008-01-20T21:30:58Z")
Make a [new action](https://community.mp3tag.de/t/967/1)
_Action type:_ **Replace with regular expressions**
_Field:_ **\_FILENAME**
_Regular expression:_ **.m4a$**
_Replace matches with:_ **.m4b**
[] case-sensitive comparison
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### Author:  [@shroppie](https://community.mp3tag.de/u/shroppie)
#### Post date: [January 22, 2008, 9:12am UTC](https://community.mp3tag.de/t/changing-file-extensions/6103/3 "2008-01-22T09:12:35Z")
Thanks Dano, Worked fine...
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### Author:  [@system](https://community.mp3tag.de/u/system)
#### Post date: [February 9, 2026, 12:20pm UTC](https://community.mp3tag.de/t/changing-file-extensions/6103/4 "2026-02-09T12:20:44Z")