highlightjs-circom

A Highlight.js language plugin that adds rich syntax highlighting for Circom — the domain-specific language used to write zero-knowledge arithmetic circuits (R1CS / SNARKs).

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Features

• Full keyword coverage: template, component, signal, input, output, bus, parallel, custom, extern_c, pragma, include, and all control-flow keywords
• Circom-specific constraint operators highlighted at high relevance: <==, ==>, <--, -->, ===
• Pragma directives (pragma circom 2.x.x, pragma custom_templates)
• Include paths highlighted as strings
• Tag annotations on signals and buses ({binary}, {edwards_point}, …)
• Built-in functions: log, assert
• Decimal and hexadecimal numeric literals
• Line and block comments
• Template, function, and bus names highlighted as title.function
• Correct auto-detection: Circom code reliably detected via highlightAuto

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Installation

npm install highlightjs-circom

highlight.js ≥ 11 is a peer dependency — install it separately if you haven't already:

npm install highlight.js

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Usage

CommonJS / Node.js

const hljs = require("highlight.js");
const circom = require("highlightjs-circom");

hljs.registerLanguage("circom", circom.default ?? circom);

const code = `
pragma circom 2.1.5;

template Multiplier(n) {
    signal input a;
    signal input b;
    signal output c;
    c <== a * b;
}
`.trim();

const html = hljs.highlight(code, { language: "circom" }).value;
console.log(html);

ES Modules

import hljs from "highlight.js";
import circom from "highlightjs-circom";

hljs.registerLanguage("circom", circom);

const result = hljs.highlight(code, { language: "circom" });

Browser (CDN)

Load Highlight.js first, then load this plugin:

<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/highlight.js/11.10.0/styles/github-dark.min.css">
<script src="https://cdnjs.cloudflare.com/ajax/libs/highlight.js/11.10.0/highlight.min.js"></script>
<!-- highlightjs-circom -->
<script src="https://unpkg.com/highlightjs-circom/dist/index.js"></script>
<script>
  hljs.registerLanguage("circom", window.hljsCircom?.default ?? window.hljsCircom);
  hljs.highlightAll();
</script>

Then mark up your code blocks:

<pre><code class="language-circom">
pragma circom 2.1.5;

template IsZero() {
    signal input in;
    signal output out;
    signal inv;
    inv <-- in != 0 ? 1/in : 0;
    out <== -in * inv + 1;
    in * out === 0;
}

component main = IsZero();
</code></pre>

Auto-detection

The plugin registers Circom with high relevance scores on constraint operators so highlightAuto correctly identifies Circom source files:

const result = hljs.highlightAuto(unknownCode);
console.log(result.language); // "circom"

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Supported syntax elements

Element	Highlight class
pragma, include	hljs-meta
Keywords (template, signal, component, …)	hljs-keyword
Constraint operators (<==, ==>, ===, …)	hljs-operator
Tag annotations {…}	hljs-type
Template / function / bus names	hljs-title function_
Built-ins (log, assert)	hljs-built_in
Literals (true, false)	hljs-literal
Numeric literals	hljs-number
String literals	hljs-string
Comments	hljs-comment

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Example

pragma circom 2.1.5;
pragma custom_templates;

include "bitify.circom";

/*
 * Computes the bitwise AND of two n-bit numbers.
 */
template BitwiseAnd(n) {
    signal {binary} input a[n];
    signal {binary} input b[n];
    signal {binary} output out[n];

    for (var i = 0; i < n; i++) {
        out[i] <== a[i] * b[i];
    }
}

component main {public [a, b]} = BitwiseAnd(8);

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Compatibility

highlight.js	highlightjs-circom
≥ 11.0.0	✓

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License

MIT © ABDK Consulting