Generate native CSS aspect-ratio rules and legacy padding-top hack fallbacks.
Execution runs 100% locally inside the browser sandbox using HTML5 Canvas, Web Cryptography Subtle API, and Web Workers. Zero egress.
Zero network latency. Operates completely offline with zero dependencies on third-party backend servers or cloud services.
Built according to official RFC specifications, cryptographic test vectors, and enterprise-grade data transformation standards.
Choose 16:9, 4:3, 1:1, 9:16, 21:9, or Custom.
Toggle @supports fallback and set image fit mode.
Copy the stylesheet directly into your project.
Aspect-ratio prevents layout shifts (CLS) by reserving exact vertical container dimensions before media assets load.
It uses the classic padding-top percentage hack inside @supports not (aspect-ratio: ...).
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