HornPDF accessibility testing at scale

Open-source PDF/UA checker based on the Matterhorn Protocol

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Blazing Fast

Process 500+ PDFs per second with parallel processing. Built in Rust for maximum throughput — validate entire document libraries in seconds, not hours.

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Matterhorn Protocol

Every failure condition of the Matterhorn Protocol 1.1 for PDF/UA-1 (ISO 14289-1) — 87 machine-checkable conditions automated, 48 human-judgment conditions surfaced for manual review, 2 without a defined test. 100% on the veraPDF PDF/UA-1 corpus.

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CI/CD Native

First-class support for SARIF (GitHub Code Scanning), JUnit XML, and JSON output. Ship accessible PDFs with every build.

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Use Anywhere

CLI, desktop app, browser (WebAssembly), npm package, GitHub Action, or Docker. One tool, every platform.

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GitHub Action

Drop-in GitHub Action with automatic SARIF upload. Add PDF accessibility checks to your workflow in two lines of YAML.

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Extensible

Add custom checks with the Check trait. Horn's modular architecture makes it easy to tailor validation to your requirements.

Performance

500+

PDFs / second

check modules

runtime dependencies