Anyone else notice Claude suddenly using British spelling?
A user in the U.S. reported that Claude, despite settings for "English (United States)," began using British spelling about two weeks ago. Examples include "Colour," "Recognise," "Enrolment," "Defence," "Analyse," and "Behaviour." When asked, Claude described this change as "drift" and stated it didn't know why. The user, who is not using a VPN, is curious if others have observed this sudden shift in spelling.
This report is among the first to document Claude's unexplained shift to British spelling, unlike previous discussions focused on model drift in other contexts.
Time & source
Times shown in UTC
Display time zone: UTC
Local time zone unavailable; showing UTC.
PublishedOffset at this time: UTC+0Sep 12, 2026, 20:54 UTC
IngestedOffset at this time: UTC+0Sep 13, 2026, 11:01 UTC
- Published
- Sep 12, 2026, 20:54
- Ingested
- Sep 13, 2026, 11:01
- Source type
- Dev community
- Tier
- Community
- Source status
- Healthy
Tier is a per-source editorial setting, not a per-item score.
I'm in the U.S. and my settings are set to "English (United States)." I noticed about two weeks ago that Claude suddenly started using mostly British spelling in both its thinking summaries and responses.
A few examples:
- Colour
- Recognise
- Enrolment
- Defence
- Analyse
- Behaviour
I asked Claude why the spelling had changed, and it said it didn't know and described it as "drift."
It doesn't really affect anything, but I'm curious whether anyone else has noticed the same thing recently?
EDIT: I'm not using a VPN.