New ChatGPT Models Seem to Leave Watermarks on Text

Summary

What's Going OnOur team at Rumi has discovered that the newer and more advanced GPT-o3 and o4-mini models appear to be embedding special character watermarks in generated text. In our testing, the watermarks were only added to longer responses for example when asking GPT-o3 to "Write a full essay on the Department of Education". These watermarks consist of special Unicode characters (primarily the Narrow No-Break Space) that look identical to regular spaces but have different ASCII-codes. In our testing we did not observe watermarks in older models such as GPT-4o.Users can detect these hidden characters by pasting text into online tools like this or text editors like Sublime Text, which reveal these normally invisible markers. The pattern of these characters appears to be systematic rather than random, suggesting an intentional implementation.Using a code editor to spot watermarks‍This comes on the heels of recent announcements of OpenAI testing with watermarks on images. OpenAI has made no official announcement about this feature, likely because publicizing it would undermine its effectiveness in detecting plagiarism. While potentially useful for identifying AI-generated content, the watermarking is relatively easy to circumvent once users are aware of it - a simple find-and-replace operation can remove these special characters.Why is this ImportantChatGPT is now free for students until the end of May (chatgpt.com/students). Many, if not most, students will likely use it for their work, particularly the newer and more advanced models. The timing is significant—coming during final projects and papers.Students who are unaware of these invisible markers and directly copy/paste ChatGPT-generated content as their own work may face consequences once word spreads that instructors can use specialized tools to detect these characters. However students that become aware of this change will have a significant advantage in incorporating entire ChatGPT answers as their own answ...