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Playground

The reference implementation runs in your browser (tree-sitter as WebAssembly, the evaluator as JavaScript), through the same session the REPL and the language server use. Edit the module and the outputs and diagnostics update as you type; diagnostics are also marked in place, in the module and in a document. When the module declares an input, an Inputs panel opens under the editor: paste a JSON document there to bind it, and the bound document is evaluated and validated like any output. The example picker includes the tutorials with their documents, and Copy link carries the module and its documents. Single-module only: import needs a file system.

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© 2026 Luuvish. Decl is open source under the MIT License.

Type: Literata and IBM Plex, under the SIL Open Font License. Built with Astro Starlight.