Codex

At a glance

Images

Content CredentialsA signed record (C2PA) of how the file was made, sealed so any change shows.

OpenAI's provenance help article, updated October 12, 2026, says images generated with Codex include Content Credentials (C2PA) and a SynthID watermark, though coverage may vary by product, model, export path, file type and when the content was created.

Provenance signals in OpenAI-generated contentOpenAI (OpenAI Help Center)

Quoted passage Which provenance signals does OpenAI use? (table row: Images; note beneath the table)

Images Content Credentials and SynthID watermarks Images generated with ChatGPT, Codex, or the OpenAI API include both signals. […] Coverage may vary by product, model, export path, file type, and when the content was created. API outputs are covered except for models planned for imminent deprecation, including gpt-image-1, gpt-image-1.5, and sora-2.

Invisible watermarkA signal woven into the pixels, frames, audio or wording, meant to survive copying.

OpenAI says images generated with Codex include a SynthID watermark, which it announced on May 19, 2026, starting with images.

Provenance signals in OpenAI-generated contentOpenAI (OpenAI Help Center)

Quoted passage Which provenance signals does OpenAI use? (table row: Images; note beneath the table)

Images Content Credentials and SynthID watermarks Images generated with ChatGPT, Codex, or the OpenAI API include both signals. […] Coverage may vary by product, model, export path, file type, and when the content was created. API outputs are covered except for models planned for imminent deprecation, including gpt-image-1, gpt-image-1.5, and sora-2.

Advancing content provenance for a safer, more transparent AI ecosystemOpenAI

Quoted passage A multi-layered approach to provenance with Google SynthID for images

To make provenance more resilient, we are taking a multi-layered approach and incorporating watermarking through Google DeepMind’s SynthID […] SynthID embeds an invisible watermarking layer that complements C2PA metadata-based approaches.

AI label in metadataA plain metadata field (IPTC Digital Source Type) saying AI made the content. Anyone can add or remove it.

Not stated. None of OpenAI's pages listed under Sources read says so.

Visible markA mark you can see, such as a logo or a sparkle in a corner.

Not stated. None of OpenAI's pages listed under Sources read says so.

Tool named in metadataThe tool or model written into ordinary file fields, such as Software or Creator.

Not stated. None of OpenAI's pages listed under Sources read says so.

Text

Content CredentialsA signed record (C2PA) of how the file was made, sealed so any change shows.

Not stated. None of OpenAI's pages listed under Sources read says so.

Invisible watermarkA signal woven into the pixels, frames, audio or wording, meant to survive copying.

On October 5, 2026 OpenAI said it would add an invisible watermark to eligible Codex text output in the European Union over the coming weeks.

OpenAI's provenance article, dated October 12, 2026, describes EU text watermarking for ChatGPT and does not mention Codex.

Our approach to EU text provenance rulesOpenAI

Quoted passage Introduction (phased approach list)

Starting today, API customers globally will be able to opt in to text watermarking for select models. Text watermarking will remain off by default in the API. Over the coming weeks, we will add an invisible watermark to eligible ChatGPT and Codex text output in the European Union.

Provenance signals in OpenAI-generated contentOpenAI (OpenAI Help Center)

Quoted passage Which provenance signals does OpenAI use? (table row: Text)

Text textGrain watermarks (EU only) In the EU, ChatGPT-generated text includes an invisible change to the randomness used in the model’s word choices to comply with the EU AI Act. API customers globally can turn on text watermarks to text outputs, from their project or organization settings.

AI label in metadataA plain metadata field (IPTC Digital Source Type) saying AI made the content. Anyone can add or remove it.

Not stated. None of OpenAI's pages listed under Sources read says so.

Visible markA mark you can see, such as a logo or a sparkle in a corner.

Not stated. None of OpenAI's pages listed under Sources read says so.

Tool named in metadataThe tool or model written into ordinary file fields, such as Software or Creator.

Not stated. None of OpenAI's pages listed under Sources read says so.

Documents and code

Content CredentialsA signed record (C2PA) of how the file was made, sealed so any change shows.

Not stated. None of OpenAI's pages listed under Sources read says so.

Invisible watermarkA signal woven into the pixels, frames, audio or wording, meant to survive copying.

Not stated. None of OpenAI's pages listed under Sources read says so.

OpenAI does not say that code Codex writes carries a watermark. It says code is harder to watermark.

AI label in metadataA plain metadata field (IPTC Digital Source Type) saying AI made the content. Anyone can add or remove it.

Not stated. None of OpenAI's pages listed under Sources read says so.

Visible markA mark you can see, such as a logo or a sparkle in a corner.

Not stated. None of OpenAI's pages listed under Sources read says so.

Tool named in metadataThe tool or model written into ordinary file fields, such as Software or Creator.

Not stated. None of OpenAI's pages listed under Sources read says so.

Limits and detection

Checking tool from the makerA way the maker offers to check a file for its traces.

OpenAI's verification page at openai.com/verify looks for C2PA metadata and SynthID watermarks in content generated with ChatGPT, the OpenAI API or Codex, and currently supports images and audio.

Verify OpenAI-generated contentOpenAI

Quoted passage What does this tool do?; What content can it detect?

This tool checks whether an uploaded file contains provenance signals associated with OpenAI tools. It looks for supported signals, including C2PA metadata and SynthID watermarks, and reports whether they are detected. […] The tool is designed to detect content generated with ChatGPT, the OpenAI API, or Codex. It currently supports images and audio files.

What the maker says about limitsIn the maker's own words.

OpenAI says code is harder to watermark, and that short passages usually do not contain enough text for reliable watermark detection.

Provenance signals in OpenAI-generated contentOpenAI (OpenAI Help Center)

Quoted passage Do text watermarks apply to short answers and code?

Short passages usually do not contain enough text for reliable watermark detection. Code is also harder to watermark because there are fewer plausible choices for what comes next than in ordinary prose.