gss/engine

Health v2 · maintenance only

Adoption not part of the score

2853 stars · 100 forks observed · 2026-08-28

What it is AI-extracted, prompt v1, taxonomy v1, 2026-08-30, confidence not recorded

GSS (Grid Style Sheets) is a JavaScript engine that compiles and runs constraint-based layout rules for the DOM, implementing Constraint Cascading Style Sheets via the Cassowary constraint solver. It supports CCSS constraints and Apple's Visual Format Language to express relational positioning and sizing between elements.

Use cases

• center an element within another with a one-liner
• define relational layout rules between DOM elements
• replace CSS layout with constraint-based positioning
• use Apple's Visual Format Language for web layout
• solve cyclic layout dependencies between elements
• build responsive layouts from size and position constraints

When to choose

• you need declarative relational constraints between elements rather than parent-relative CSS positioning
• you want Cassowary-style constraint solving like Apple's Auto Layout in the browser
• you're maintaining an existing GSS codebase

When to avoid

• starting a new project — modern CSS Flexbox and Grid cover most needs and GSS is no longer actively developed
• you need guaranteed long-term support or recent browser feature integration
• performance-critical pages where a JS layout solver runtime would add overhead

Facets

library · maturity maintenance

ui-components css-framework compiler web-development frontend web-design browser constraint-solver layout-engine cassowary visual-format-language ccss css-polyfill coffeescript nodejs javascript

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For agents

markdown · JSON · MCP: product_card(name="gss/engine")