File Manager incorrectly detects valid UTF-8 files as GB18030

Cesar Lopes

• July 27, 2026 13:15

Hello,

I’m seeing an encoding detection issue in cPanel File Manager on:

 

cPanel & WHM 11.136.0.31

 

A file that is valid UTF-8 is being detected as gb18030 when opening it through File Manager.

For example:

 

file -bi /home/CLIENTE/laravel/.env

 

returns:

 

text/plain; charset=utf-8

 

And:

 

file --mime-encoding /home/CLIENTE/laravel/.env

 

returns:

 

utf-8

 

UTF-8 validation also succeeds:

 

iconv -f UTF-8 -t UTF-8 /home/CLIENTE/laravel/.env >/dev/null 2>&1
echo $?

 

returns:

 

0

 

The newer Fileman API also identifies the file correctly:

 

uapi --user=CLIENTE Fileman get_file_content \
dir=/home/CLIENTE/laravel \
file=.env

 

returns:

 

from_charset: utf-8
to_charset: utf-8

 

However, the encoding detection used by File Manager returns:

 

cpapi2 --user=CLIENTE Encoding guess_file \
file=laravel%2F.env

 

result:

 

encoding: gb18030

 

I traced this to:

 

/usr/local/cpanel/bin/guess_file_encoding

 

Running it directly reproduces the problem:

 

/usr/local/cpanel/bin/guess_file_encoding /home/CLIENTE/laravel/.env

 

returns:

 

gb18030

 

The script uses:

 

Encode::Detect::Detector::detect($buffer)

 

So it appears that Encode::Detect::Detector is producing a false positive for GB18030, even though the file contains valid UTF-8.

The File Manager template also appears to call Encoding::guess_file_opts when the charset is set to _DETECT_, so this incorrect result becomes the default encoding shown in the editor.

I considered adding a UTF-8 validity check before calling Encode::Detect::Detector, so that:

 

valid UTF-8 -> utf-8
otherwise   -> Encode::Detect::Detector

 

Before modifying a cPanel-managed file, I would like to know:

1. Is this a known issue?
2. Is there a supported setting to prefer UTF-8 when it is valid?
3. Is there an official workaround or patch?
4. Would checking for valid UTF-8 before calling Encode::Detect::Detector be considered a safe workaround?

Character encoding verification in File Manager is enabled. This is therefore different from the older _DETECT_ conversion issue caused by disabling encoding verification.

Thank you.

• 

  cPRex Jurassic Moderator

  • July 27, 2026 16:32

  Hey there!  This is actually a known issue as certain special characters, which are likely present in that .env file, cause the guess_file_encoding tool to detect the wrong encoding value.

  We do have an older case on this at CPANEL-39433 and I've reached out to the development team to see if we can get some movement on this.  Thanks for bringing this up!

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