# Cannot Change File Extension
**URL:** https://community.mp3tag.de/t/cannot-change-file-extension/63818
**Category:** Support
**Created:** [February 17, 2024, 7:46pm UTC](https://community.mp3tag.de/t/cannot-change-file-extension/63818 "2024-02-17T19:46:14Z")
**Posts on this page:** 3
**Page:** 1
### Author:  [@cldcp00](https://community.mp3tag.de/u/cldcp00)
#### Post date: [February 17, 2024, 7:46pm UTC](https://community.mp3tag.de/t/cannot-change-file-extension/63818/1 "2024-02-17T19:46:14Z")
Something that I expected to be fairly simple is beginning to give me a headache.
I just want to change the file extension from \*.MP3 upper place to \*.mp3 lowercase.
I'm tried using the Replace command and it doesn't seem to work, nothing I seem to try works.
Has anyone got an action that does this successfully please
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### Author:  [@Florian](https://community.mp3tag.de/u/Florian)
#### Post date: [February 17, 2024, 8:02pm UTC](https://community.mp3tag.de/t/cannot-change-file-extension/63818/2 "2024-02-17T20:02:15Z")
Yes, the action from the first post of this topic does this successfully
> [@Change file extension to lowercase - Regular expression](https://community.mp3tag.de/t/change-file-extension-to-lowercase-regular-expression/59816):
>
> Seems like the regular expression thread is locked Previously found some nice examples there, why was it closed? Not an overly complex one but couldn't find it so posting here in case it's useful to someone else: Had a number of uppercase file extensions and was looking to convert them all to lowercase; there doesn't seem to be such a thing as the '"file extension" field so here's my take on it: Field : \_FILENAME Regular expression : \.(.\*)$ Replace with : .$lower($1) Cheers,
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### Author:  [@system](https://community.mp3tag.de/u/system)
#### Post date: [March 18, 2024, 8:03pm UTC](https://community.mp3tag.de/t/cannot-change-file-extension/63818/3 "2024-03-18T20:03:13Z")
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