# PsychoPy 2026.2.4 fails to start on Japanese Windows 11 due to UTF-8 / cp932 issue

**URL:** <https://discourse.psychopy.org/t/psychopy-2026-2-4-fails-to-start-on-japanese-windows-11-due-to-utf-8-cp932-issue/48214>\
**Category:** Other\
**Created:** [October 23, 2026, 2:35am UTC](https://discourse.psychopy.org/t/psychopy-2026-2-4-fails-to-start-on-japanese-windows-11-due-to-utf-8-cp932-issue/48214 "2026-10-23T02:35:07Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![lupus\_Canis](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.psychopy.org/lupus_canis/32/46864_2.png) [@lupus\_Canis](https://discourse.psychopy.org/u/lupus_Canis)\
**Post date:** [October 23, 2026, 2:35am UTC](https://discourse.psychopy.org/t/psychopy-2026-2-4-fails-to-start-on-japanese-windows-11-due-to-utf-8-cp932-issue/48214/1 "2026-10-23T02:35:07Z")

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FYI

PsychoPy 2026.2.4  
Windows 11 Japanese

PsychoPy would not start at all after installation.

Running:

import psychopy.app  
psychopy.app.startApp()

raised:

UnicodeDecodeError: ‘cp932’ codec can’t decode byte 0xef …

The problem was in:

Lib/site-packages/i18next/base.py

Changing the file opening to:

encoding=“utf-8-sig”

resolved the issue.

Locale:  
(‘ja\_JP’, ‘cp932’)

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**Author:** ![lupus\_Canis](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.psychopy.org/lupus_canis/32/46864_2.png) [@lupus\_Canis](https://discourse.psychopy.org/u/lupus_Canis)\
**Post date:** [October 23, 2026, 3:16am UTC](https://discourse.psychopy.org/t/psychopy-2026-2-4-fails-to-start-on-japanese-windows-11-due-to-utf-8-cp932-issue/48214/2 "2026-10-23T03:16:16Z")

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Hi, agein.  
Additional note:

After fixing the UTF-8 issue, PsychoPy starts.

However, the GUI remains entirely in English.

I checked:

D:\Program Files\PsychoPy\Lib\site-packages\psychopy\localization\locales\ja-JP.json

and it only contains one translation entry:

“Welcome to PsychoPy!”

For example:

from psychopy.localization import \_translate  
print(\_translate(“File”))

returns:

File

so it appears the Japanese localization file is largely empty.

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**Author:** ![JensBoelte](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.psychopy.org/jensboelte/32/9060_2.png) [@JensBoelte](https://discourse.psychopy.org/u/JensBoelte)\
**Post date:** [October 23, 2026, 10:56am UTC](https://discourse.psychopy.org/t/psychopy-2026-2-4-fails-to-start-on-japanese-windows-11-due-to-utf-8-cp932-issue/48214/3 "2026-10-23T10:56:26Z")

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Hello @lupus_Canis

That could well be. If you want to contribute a Japanese localization take a look here [Translations — PsychoPy®](https://psychopy.org/developers/localization.html)

Best wishes Jens

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**Author:** ![wakecarter](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.psychopy.org/wakecarter/32/5753_2.png) [@wakecarter](https://discourse.psychopy.org/u/wakecarter)\
**Post date:** [October 23, 2026, 11:01am UTC](https://discourse.psychopy.org/t/psychopy-2026-2-4-fails-to-start-on-japanese-windows-11-due-to-utf-8-cp932-issue/48214/4 "2026-10-23T11:01:17Z")

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Thank you. I highlighted this post to @TParsons who has discovered a bug which should be fixed in the next release (2026.2.5 coming soon).