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SignUnder

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Sign AI-generated images under your own name: C2PA Content Credentials, an invisible watermark and a public verification page. Open source.

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Since

  • New

Updated

  • Updated Oct 2026

Platforms

  • Self-Hosted
  • Software as a Service (SaaS)
  • Docker
  • Online
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SignUnder information

  • Developed by

    IE flagAivaStack

  • Licensing

    Open Source (Apache-2.0) and Freemium product.

  • Pricing

    Subscription ranging between $449 and $1490 per month + free version with limited functionality.

  • Written in

  • Alternatives

    1 alternative listed

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  • Supported Languages

    • English

GitHub repository

  •  1 Stars
  •  0 Forks
  •  0 Open Issues
  •   Updated  
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SignUnder was added to AlternativeTo by AivaStack on and this page was last updated .

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What is SignUnder?

SignUnder marks AI-generated images so a company can show where they came from and meet labelling rules such as Article 50 of the EU AI Act. Each image gets three marks: a C2PA manifest (Content Credentials) signed with a key held in a hardware security module, an invisible TrustMark watermark, and a PDQ perceptual fingerprint, so it can still be matched after a platform strips the metadata. Once the company proves its domain, every signature names it. Anyone can check an image on the company's public verification page.

The whole service is open source under Apache-2.0 (a .NET API, a Rust signer built on c2pa-rs, a Python watermark worker, and .NET and Python SDKs) and runs locally with Docker Compose. The hosted version adds the HSM-held keys, identity checks and rule packs kept current against their legal sources.