# How to edit m4a ©prf tag
**URL:** https://community.mp3tag.de/t/how-to-edit-m4a-prf-tag/67712
**Category:** Support
**Created:** [March 2, 2025, 1:17pm UTC](https://community.mp3tag.de/t/how-to-edit-m4a-prf-tag/67712 "2025-03-02T13:17:07Z")
**Posts on this page:** 8
**Page:** 1
### Author:  [@RoonJ](https://community.mp3tag.de/u/RoonJ)
#### Post date: [March 2, 2025, 1:17pm UTC](https://community.mp3tag.de/t/how-to-edit-m4a-prf-tag/67712/1 "2025-03-02T13:17:07Z")
I want to edit m4a file's ©prf tag value, but I can't read or find ©prf tag by mp3tag. kid 3 can read ©prf tag. so I am sure my m4a file has ©prf tag. is it a bug of mp3tag?
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### Author:  [@LyricsLover](https://community.mp3tag.de/u/LyricsLover)
#### Post date: [March 2, 2025, 2:09pm UTC](https://community.mp3tag.de/t/how-to-edit-m4a-prf-tag/67712/2 "2025-03-02T14:09:26Z")
You can have a look here:
> **[Tag Field Mappings – Mp3tag Documentation](https://docs.mp3tag.de/mapping/)**
>
> Overview of all available tag fields, their names in Mp3tag, and how they are mapped to the internal structures of the different tag formats. Mp3tag is the universal Tag Editor.
to check what kind of m4a ©abc fields are already available.
What exactly would ©prf contain?
Update with some more detailed information:
_(thanks for the hint to @ohrenkino)_
> [@MP4-Felder (Atom/Box) in anderer Software](https://community.mp3tag.de/t/mp4-felder-atom-box-in-anderer-software/48614/2):
>
> FFmpeg Field in Mp3tag ID3v2.3/4 MP4 FFmpeg AVI FourCC TVEPISODEID tven episode\_id TVEPISODE tves (episode\_sort) TVSEASON tvsn (season\_number) DISCNUMBER TPOS disk disc TRACK TRCK trkn track IPRT CONTENTGROUP ©grp grouping CONTENTGROUP TIT1 — TITLE TIT2 ©nam title INAM TITLESORT TSOT sonm title-sort, (sort\_name) TVSHOW tvsh show ALBUM TALB ©alb album IPRD ALBUMSORT TSOA soal album-sort, (sort\_album) ARTIST TPE1 artist IART ARTIST ©art (©ART) a…
So **`©prf`** would be the fieldname for `performers` .
This atom is currently not supported by Mp3tag up to version v3.28e.
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### Author:  [@AreDigg](https://community.mp3tag.de/u/AreDigg)
#### Post date: [March 2, 2025, 5:50pm UTC](https://community.mp3tag.de/t/how-to-edit-m4a-prf-tag/67712/3 "2025-03-02T17:50:08Z")
There are a wide variety of tags that mp4 files could have. Most are based on what Apple included in their software. ©prf is for performers
Here are a somewhat exhaustive list [QuickTime Tags](https://exiftool.org/TagNames/QuickTime.html)
MP3Tag don’t include it afaik, but @Florian may device to add it.
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### Author:  [@RoonJ](https://community.mp3tag.de/u/RoonJ)
#### Post date: [March 3, 2025, 1:48am UTC](https://community.mp3tag.de/t/how-to-edit-m4a-prf-tag/67712/4 "2025-03-03T01:48:22Z")
Thanks for reply, ©prf is "performer". mp3tag doesn't seem to support reading ©prf yet. But ©pub is ok. Is there a chance that it will be supported in the next version?
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### Author:  [@Florian](https://community.mp3tag.de/u/Florian)
#### Post date: [March 4, 2025, 9:49am UTC](https://community.mp3tag.de/t/how-to-edit-m4a-prf-tag/67712/5 "2025-03-04T09:49:58Z")
In my experience, `©prf` is not very widely supported. In fact, I don't know any app that displays this as **Performer** (even kid3, referenced in the original post, displays the atom id and not a mapped name). Do you know how this field was added to the files and which apps are currently supporting this?
Mapping `©prf` to `PERFORMER` would result in any existing custom field `PERFORMER` (which is read and listed by any app that supports flexible tagging via custom fields, e.g., foobar2000) be written as `©prf` MP4 atom when saving any changes.
As a consequence, this would result in this field not being visible anymore for apps that don't support the `©prf` MP4 atom.
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### Author:  [@RoonJ](https://community.mp3tag.de/u/RoonJ)
#### Post date: [March 5, 2025, 2:18am UTC](https://community.mp3tag.de/t/how-to-edit-m4a-prf-tag/67712/6 "2025-03-05T02:18:41Z")
The reason for modifying ©prf is that Roon will read ©prf first. Although PERFORMER can be modified, only the original value of ©prf is displayed in Roon. I tried to map ©prf to PERFORMER, but the modified result is still only written to PERFORMER tag. Is there any other way to modify it by mp3tag?
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### Author:  [@Florian](https://community.mp3tag.de/u/Florian)
#### Post date: [March 5, 2025, 2:02pm UTC](https://community.mp3tag.de/t/how-to-edit-m4a-prf-tag/67712/7 "2025-03-05T14:02:31Z")
> [@RoonJ](#):
>
> The reason for modifying ©prf is that Roon will read ©prf first.
So if you remove this and only have PERFORMER, Roon will read this field?
> [@RoonJ](#):
>
> Is there any other way to modify it by mp3tag?
No, unfortunately not.
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### Author:  [@system](https://community.mp3tag.de/u/system)
#### Post date: [August 26, 2025, 12:51pm UTC](https://community.mp3tag.de/t/how-to-edit-m4a-prf-tag/67712/8 "2025-08-26T12:51:10Z")
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