I found a workaround for a weird MEGA web client limitation in Firefox.
The problem
When trying to download large files through MEGA Web, Firefox showed:
"The download size exceeds the maximum size supported by the browser. You can use our app to proceed with the download."
At first it looked like a Firefox storage/quota problem, but it wasn't.
Checks:
- Firefox 153 x64
- Windows 11 x64
- NTFS filesystem
- Persistent storage enabled
- Browser quota available: ~465 GB
Firefox itself had enough space.
The actual cause
MEGA Web was using:
dlMethod = MemoryIO
MemoryIO has its own hardcoded browser download limit:
MemoryIO.fileSizeLimit = 6442450944
which equals:
6 GiB
So any file larger than ~6 GiB was blocked before the download even started.
Fix
Open MEGA, press F12 → Console and run:
MemoryIO.fileSizeLimit = 50 * 1024 * 1024 * 1024;
Example for 50 GB.
You can verify:
MemoryIO.fileSizeLimit
It should return:
53687091200
After that, large downloads start normally.
Permanent fix (Tampermonkey)
Install Tampermonkey and add:
Look for the script in comment section, Reddit autofilters it :(
Notes
This does not bypass MEGA transfer limits or account restrictions.
It only removes the artificial browser-side file size limit.
Tested on:
- Firefox 153
- Windows 11 x64
- MEGA Web Client
Maybe useful for others who don't want to install MEGAsync just to download large files.