OpenAI to watermark EU-generated ChatGPT and Codex text and code
OpenAI has announced it will add an invisible watermark to text and code generated within the European Union to comply with the region's new AI Act transparency requirements. The measure follows similar steps taken by Anthropic earlier this year, as major AI firms work to meet an EU mandate that generative AI outputs be identifiable by machines.
The watermark system, called textGrain, adds statistical signals to model word choices that detectors can identify. However, OpenAI acknowledges significant limitations: it achieves only about 80 per cent success on shorter text or mathematical content, with further drops when text is edited. The watermark will be enabled by default for ChatGPT and Codex outputs in the EU, and the company plans to release the technology as open source, though detector access will initially be restricted to approved researchers. Companies must comply with the EU AI Act requirement by December 2, 2026.
- OpenAI will watermark EU-generated text to comply with new AI transparency rules.
- Detection success falls to 80 per cent for shorter text and mathematics.
- Compliance deadline for all firms is December 2, 2026.
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The European Union has introduced regulations requiring AI companies to make their systems' outputs identifiable. This transparency rule is designed so that users can tell when text or code has been created by artificial intelligence rather than by a person. The requirement reflects concerns that AI-generated content could be confused with human-made material, potentially misleading readers or users.
To comply with this requirement, major AI companies are now embedding invisible watermarks into text generated within the EU. These watermarks work by adjusting the subtle patterns in how the AI system selects words, in a way that detection software can identify but that ordinary readers cannot notice. Several companies, including Anthropic and OpenAI, have already announced watermarking systems to meet these new rules.
However, watermarking technology has significant limitations. It is less effective on short texts or mathematical content, and can fail if someone edits the generated material. Despite these limitations, the technology is being deployed across the industry as companies work to comply with European regulations that take effect in December 2026.
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The strongest fair case each way — we don't pick a winner.
The case for
Transparency about AI-generated content is essential for public trust and informed decision-making, particularly given AI's growing influence on information and commerce. Whilst an 80 per cent detection rate is imperfect, it represents meaningful progress and regulatory mandates drive faster improvement than voluntary adoption; incremental accountability mechanisms are preferable to deploying powerful systems with no transparency safeguards. The EU's approach balances legitimate oversight needs with continued innovation.
The case against
An 80 per cent detection rate that deteriorates further with editing cannot reliably achieve the regulation's stated aims, making this requirement largely performative rather than protective. Imposing substantial compliance costs on companies to deploy a tool that fails consistently is a misallocation of regulatory effort; resources would be better invested in alternative solutions such as digital authentication systems and content provenance tracking that directly prevent fraud and misinformation. Rather than accepting technical imperfection as acceptable, regulators should pursue infrastructure solutions that actually address the underlying problems.
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Originally published by Engadget as “OpenAI will add a digital watermark to text and code generated in the EU”.