Nuri

Nuri is a pure Go port of Shiki, the TextMate grammar-based syntax highlighter used by VS Code. It runs the real Oniguruma regex engine compiled to WASM via wazero, a pure Go WASM runtime. No CGO, no Node.js, no subprocess.

257 languages, 65 themes, full TextMate grammar support. 227 of 234 tested grammars (97%) produce output byte-identical to Shiki; the core bundle's 32 fidelity-tested grammars are at 100%.

Minimal example

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package main
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import (
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  "context"
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  "fmt"
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  "log"
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  "github.com/frostybee/nuri"
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  "github.com/frostybee/nuri/bundle/core"
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)
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func main() {
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  ctx := context.Background()
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  h, err := nuri.New(ctx, nuri.WithFS(core.FS()))
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  if err != nil {
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    log.Fatal(err)
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  }
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  defer h.Close(ctx)
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  html, err := h.CodeToHTML(ctx, `fmt.Println("hello, world")`, nuri.CodeToHTMLOptions{
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    Lang:  "go",
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    Theme: "github-dark",
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  })
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  if err != nil {
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    log.Fatal(err)
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  }
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  fmt.Println(html)
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}

Output:

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<pre class="nuri github-dark" style="background-color:#24292e;color:#e1e4e8" tabindex="0"><code><span class="line"><span style="color:#E1E4E8">fmt.</span><span style="color:#79B8FF">Println</span><span style="color:#E1E4E8">(</span><span style="color:#9ECBFF">"hello, world"</span><span style="color:#E1E4E8">)</span></span></code></pre>

What Nuri provides

• Six output formats via h.CodeToHTML(), h.CodeToANSI(), h.CodeToSVG(), h.CodeToJSON(), h.CodeToPlainText(), and h.CodeToTokens()
• Multi-theme mode that tokenizes once and resolves multiple themes through CSS variables
• Transformer pipeline with built-in support for notation comments ([!code ++], [!code highlight]), meta string ranges, visible whitespace, and custom hooks
• Style-to-class mode replacing inline styles with deterministic hashed class names
• WCAG 2.1 contrast correction that adjusts foreground colors against the theme background (default ratio 5.5)
• Concurrency-safe bounded pool of WASM instances for parallel highlighting
• Language detection by file extension, exact filename, or first-line shebang
• Two bundle sizes: bundle/core (38 languages, ~0.5 MB) and bundle/full (257 languages, ~1.5 MB)

Where to go next

• Installation and Quick Start to set up and run Nuri
• Guides for task-oriented walkthroughs: themes, output formats, transformers, line decorations, and more
• Reference for complete API documentation: every method, option, and type