# MP3 file serial number?

**URL:** https://community.mp3tag.de/t/mp3-file-serial-number/57671
**Category:** Support
**Created:** [June 19, 2022, 2:48pm UTC](https://community.mp3tag.de/t/mp3-file-serial-number/57671 "2022-06-19T14:48:15Z")
**Posts on this page:** 1
**Showing post:** 17

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### Author: ![LyricsLover](https://community.mp3tag.de/letter_avatar_proxy/v4/letter/l/c6cbf5/32.png) [@LyricsLover](https://community.mp3tag.de/u/LyricsLover)
#### Post date: [June 21, 2022, 1:19pm UTC](https://community.mp3tag.de/t/mp3-file-serial-number/57671/17 "2022-06-21T13:19:18Z")

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> [@ohrenkino](#):
>
> Load all files  
> Select all files  
> User Converter\>Tag-Tag  
> for Field type in: SERIAL\_NUMBER  
> Format string: $num(%\_counter%,6)

Another idea could be to fill a random number with always 5 digits with  
`$num($rand(),5)`

The randomness seems to be improved [since v3.13](https://community.mp3tag.de/t/rand-function-bug-always-naming-first-and-second-0041-and-1846/56760/4), but I would not garantuee if you use this function for lets say 99999 tracks that you never get a duplicated number. I could not find a way to tell this function to generate a value with 6 or more digits - maybe you could fill your user defined tag like this:  
`$num($rand(),5) - $num($rand(),5) - $num($rand(),5)`

As long as this duplicate doesn't appear for the same folder it should not be a problem.

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_[View the full topic](https://community.mp3tag.de/t/mp3-file-serial-number/57671)._