# Can't access MP4 files
**URL:** https://community.mp3tag.de/t/cant-access-mp4-files/71094
**Category:** Support
**Created:** [April 21, 2026, 7:21pm UTC](https://community.mp3tag.de/t/cant-access-mp4-files/71094 "2026-04-21T19:21:13Z")
**Posts on this page:** 11
**Page:** 1
### Author:  [@LarsErikOsterud](https://community.mp3tag.de/u/LarsErikOsterud)
#### Post date: [April 21, 2026, 7:21pm UTC](https://community.mp3tag.de/t/cant-access-mp4-files/71094/1 "2026-04-21T19:21:14Z")
I cut some MP4 files in LosslessCut.
Now I get an error message when trying to edit them in Mp3tag.
But I have done this many times before without this beeing an issue.
Now all the new files refuse to be written to in Mp3tag.
Error message says litt useful. Only “File cannot be opened for writing”.
Is there any way to get som more info on WHY it cannot be written?
PS! File works in all other programs. Just Mp3tag that refuse.
One more info. In the column where it usually says “MP4 (MP4)” these file are blank? Why?
Have compared file info (in MPC-HC) with a file that can be written, and looks the same.
---
### Author:  [@ohrenkino](https://community.mp3tag.de/u/ohrenkino)
#### Post date: [April 21, 2026, 7:27pm UTC](https://community.mp3tag.de/t/cant-access-mp4-files/71094/2 "2026-04-21T19:27:46Z")
Do you see an exclamation mark in the first column of the file list?
That would mean that MP3tag considers the file to be corrupt.
See also here:
> [@How to check files for errors?](https://community.mp3tag.de/t/how-to-check-files-for-errors/44633):
>
> It’s required and often helps to reduce support cycles to check files for errors before filing a bug report. Symptoms of erroneous files are often missing or wrong bitrate or length audible blips or skips tags seem to be sticky and cannot be removed There are some really good tools to check the files for errors, namely MP3 Diags — identifies many different issues in MP3 files Website: [http://mp3diags.sourceforge.net](http://mp3diags.sourceforge.net) Download: [MP3 Diags - Getting MP3 Diags](http://mp3diags.sourceforge.net/010_getting_the_program.html#binWindows) If the font size in MP3 Diags is …
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### Author:  [@LyricsLover](https://community.mp3tag.de/u/LyricsLover)
#### Post date: [April 21, 2026, 7:38pm UTC](https://community.mp3tag.de/t/cant-access-mp4-files/71094/3 "2026-04-21T19:38:31Z")
Could you provide one of the files for which you receive the message "File cannot be opened for writing"?
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### Author:  [@LarsErikOsterud](https://community.mp3tag.de/u/LarsErikOsterud)
#### Post date: [April 21, 2026, 7:41pm UTC](https://community.mp3tag.de/t/cant-access-mp4-files/71094/4 "2026-04-21T19:41:23Z")
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### Author:  [@LarsErikOsterud](https://community.mp3tag.de/u/LarsErikOsterud)
#### Post date: [April 21, 2026, 7:45pm UTC](https://community.mp3tag.de/t/cant-access-mp4-files/71094/5 "2026-04-21T19:45:58Z")
Hmmm… Wonder if the file is intact when uploaded here….
Otherwize I can put it on GoogleDrive and link to it?
Edit: I tried to save it from here, and then edit in Mp3tag. Same error.
But it plays OK in all players… So I can’t get why it cannont be written.
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### Author:  [@ohrenkino](https://community.mp3tag.de/u/ohrenkino)
#### Post date: [April 21, 2026, 7:54pm UTC](https://community.mp3tag.de/t/cant-access-mp4-files/71094/6 "2026-04-21T19:54:36Z")
A check of this file with foobar2000 and optimizing the file layout leads to this response:
```auto
Suspicious behavior, file became larger instead of shrinking!
file://C:\Users\me\Downloads\Jahn Teigen, Anita Skorgan - Adiue.mp4
Old size: 2631436 bytes, new size: 2635524
1 file processed.
Total file size increased by 4088 bytes.
```
So Foobar2000 also sees problems with the file
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### Author:  [@LarsErikOsterud](https://community.mp3tag.de/u/LarsErikOsterud)
#### Post date: [April 21, 2026, 7:55pm UTC](https://community.mp3tag.de/t/cant-access-mp4-files/71094/7 "2026-04-21T19:55:00Z")
If I recode the file in Handbrake then it acts normal.
But that will reduce the quality. So that is not an option.
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### Author:  [@LarsErikOsterud](https://community.mp3tag.de/u/LarsErikOsterud)
#### Post date: [April 21, 2026, 7:57pm UTC](https://community.mp3tag.de/t/cant-access-mp4-files/71094/8 "2026-04-21T19:57:01Z")
Do you have the file after the foobar2000 optimizing?
Does the optimized file act normally in Mp3tag?
Then it might be a problem with the newest version of “LosslessCut” (never been a porblem before).
What is the easiest app to use to rewrite the MP4 files without recoding anything?
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### Author:  [@ohrenkino](https://community.mp3tag.de/u/ohrenkino)
#### Post date: [April 21, 2026, 8:03pm UTC](https://community.mp3tag.de/t/cant-access-mp4-files/71094/9 "2026-04-21T20:03:13Z")
No, the file cannot be modified in MP3tag.
But I would try the older version of your program and see if the problem prevails.
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### Author:  [@Florian](https://community.mp3tag.de/u/Florian)
#### Post date: [April 22, 2026, 4:27pm UTC](https://community.mp3tag.de/t/cant-access-mp4-files/71094/10 "2026-04-22T16:27:58Z")
> [@LarsErikOsterud](#):
>
> Is there any way to get som more info on WHY it cannot be written?
I had a look at the file and it contains an invalid MP4 atom, which causes Mp3tag to refuse writing to that file.
What you can try is loading this file in foobar2000 and use **File → Properties** and remove tags via the **Tools** menu. This should also remove the erroneous MP4 atom and make the file editable in Mp3tag again.
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### Author:  [@system](https://community.mp3tag.de/u/system)
#### Post date: [April 29, 2026, 4:28pm UTC](https://community.mp3tag.de/t/cant-access-mp4-files/71094/11 "2026-04-29T16:28:42Z")
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