# Code Block

> Code to read and copy: file name, line numbers, highlighted lines and a monochrome syntax in weight and light. Copy rolls to Copied; a terminal copies its commands only.

Data display · code, syntax, copy, terminal · HTML, CSS, vanilla JS · no dependencies · updated 2026-10-16
Demo: https://kodza.dev/components/code-block/

## Files

The code below, served as files: byte for byte what the Kodza site copies (the CSS includes its theme guard).

- [`kodza-code-block.css`](https://kodza.dev/registry/code-block/kodza-code-block.css) · 10.5 KB
- [`kodza-code-block.js`](https://kodza.dev/registry/code-block/kodza-code-block.js) · 6.4 KB
- [`kodza-code-block.html`](https://kodza.dev/registry/code-block/kodza-code-block.html) · 1.2 KB · the markup, to adapt and paste into your page

**Can you run shell commands? Download the CSS and the JS, don't retype them.** Retyping costs thousands of tokens and can drop or change lines of the CSS. Put the files where your stack expects them (Use it says where: change the `-o` paths):

```bash
curl -fsSL --create-dirs -o kodza/kodza-code-block.css https://kodza.dev/registry/code-block/kodza-code-block.css
curl -fsSL --create-dirs -o kodza/kodza-code-block.js https://kodza.dev/registry/code-block/kodza-code-block.js
```

Then load the files from your page as Use it shows, instead of pasting the content. The HTML is the part you adapt (text, links, modifiers): paste it from the Code section. Copy the CSS and the JS from the Code section only if you can't run commands, exactly as they are. (Windows PowerShell: `curl.exe`.)

## API

- Root: `.kodza-code`
- Variables (set them on the root element itself: it declares its own defaults):
  - `--kz-code-bg: #0f0f0f`
  - `--kz-code-fg: rgba(255, 255, 255, 0.84)`
  - `--kz-code-bright: #ffffff`
  - `--kz-code-dim: rgba(255, 255, 255, 0.58)`
  - `--kz-code-line: rgba(255, 255, 255, 0.09)`
  - `--kz-code-mark: rgba(255, 255, 255, 0.06)`
  - `--kz-code-max-height: none`
  - `--kz-code-ease: cubic-bezier(0.22, 1, 0.36, 1)`
- Modifiers: `.kodza-code--terminal`
- Attributes:
  - `data-highlight` (e.g. `4-6`)
  - `data-lang` (e.g. `js`, `shell`)
- Lifecycle: `kodza:init` / `kodza:destroy` on `document`, with `{ detail: { root } }` to target a container.

## Dark mode

The values Kodza uses on a dark background (`#0a0a0a`). For a page that follows the system theme, add them after the component's CSS:

```css
@media (prefers-color-scheme: dark) {
  .kodza-code {
    --kz-code-bg: #161616;
    --kz-code-line: rgba(255, 255, 255, 0.12);
  }
}
```

A site with its own theme switch puts the same rules under its dark selector instead (`[data-theme="dark"] .kodza-code { … }`); a single dark section, under that section's class.

## Use it

### Plain HTML page

- CSS: `kodza/kodza-code-block.css` next to the page (the Files commands as they are), linked in `<head>`: `<link rel="stylesheet" href="kodza/kodza-code-block.css">`. Without a shell, paste it in a `<style>` in `<head>` instead. It only touches `kodza-` classes.
- HTML: where the component goes. Paste it as many times as you need: instances never interfere.
- JS: `kodza/kodza-code-block.js`, loaded with `<script src="kodza/kodza-code-block.js" defer></script>` in `<head>`. Without a shell, paste it in a `<script>` before `</body>` (or in `<head>`: it waits for the page). One copy per page, whatever the number of instances.
- Restyle with the `--kz-…` variables, set on the component's root element itself (the root declares its own defaults, so a value on an ancestor is ignored), and with the modifiers / attributes listed under API.
- Font: it takes the page's own. The Kodza look is Geist: `<link rel="stylesheet" href="https://fonts.googleapis.com/css2?family=Geist:wght@400;500;600;700&family=Geist+Mono:wght@400;500&display=swap">`.
- Content added later (AJAX navigation, a SPA route, a builder preview): start it with `document.dispatchEvent(new CustomEvent('kodza:init', { detail: { root: container } }))`; before removing it, the same call with `'kodza:destroy'` stops it and puts the original markup back.

### Claude artifact (claude.ai)

- Paste the CSS in a `<style>` and the JS in a `<script>` at the end, in the artifact itself: it loads stylesheets only from Google Fonts and scripts only from a few CDNs, so no `<link>` or `<script src>` to Kodza.
- Writing the artifact file with a shell? Insert the downloaded files (Files) with a command instead of retyping them: a line `KODZA-CSS` alone inside the `<style>`, `KODZA-JS` inside the `<script>`, then `sed -e '/^KODZA-CSS$/{r kodza/kodza-code-block.css' -e 'd' -e '}' -e '/^KODZA-JS$/{r kodza/kodza-code-block.js' -e 'd' -e '}' page.html > artifact.html`.
- Font: load Geist from Google Fonts (allowed): `<link rel="stylesheet" href="https://fonts.googleapis.com/css2?family=Geist:wght@400;500;600;700&family=Geist+Mono:wght@400;500&display=swap">`.
- Dark mode: the viewer sets `data-theme="dark"` or `"light"` on `<html>`, or nothing when it follows the system. Write the Dark mode rules twice: inside `@media (prefers-color-scheme: dark)` with `:root:not([data-theme="light"])` in front of each selector, and with `:root[data-theme="dark"]` in front of each selector.

### WordPress

- HTML: a **Custom HTML** block (or a pattern / template part). WordPress keeps this markup as it is only for users allowed to post unfiltered HTML (Administrators; Super Admins on multisite): for anyone else it strips tags such as `<svg>`, `<input>` or `<dialog>`, so add it from the theme (a pattern or template part) instead.
- CSS and JS: the downloaded files go in the theme, under `wp-content/themes/<your-theme>/kodza/` (the child theme if there is one), enqueued from its functions.php (or a code-snippets plugin):
  ```php
  add_action('wp_enqueue_scripts', function () {
    $dir = get_stylesheet_directory() . '/kodza/';
    $uri = get_stylesheet_directory_uri() . '/kodza/';
    wp_enqueue_style('kodza-code-block', $uri . 'kodza-code-block.css', [], filemtime($dir . 'kodza-code-block.css'));
    wp_enqueue_script('kodza-code-block', $uri . 'kodza-code-block.js', [], filemtime($dir . 'kodza-code-block.js'), true);
  });
  ```
  Scoped to `kodza-` classes, the CSS never touches the theme. One copy of the JS, whatever the number of blocks.
- No access to the theme files? The CSS can also go, as it is, in **Appearance → Customize → Additional CSS** (classic theme) or **Styles → Additional CSS** in the Site Editor (block theme).
- Theme with AJAX page transitions: fire `kodza:init` on the new content after each swap (and `kodza:destroy` on the old one).
- Performance plugin (WP Rocket, LiteSpeed Cache, Perfmatters…) with **Delay JavaScript execution** turned on: add `kodza` to the scripts it must not delay. Otherwise the component waits for the visitor's first scroll, tap or mouse move, and that first click can be lost.
- Colours: it takes the colour of the text around it (or keeps its own monochrome): nothing to point at the theme.
- WordPress turns straight quotes and `--` into typographic ones in the text of a Custom HTML block (not inside `<code>` or `<pre>`).

#### With Elementor

- HTML: an **HTML** widget (Elementor shows it to administrators only). It keeps the code exactly as pasted, straight quotes included.
- CSS and JS: as above. Elementor's Site Settings → Theme Style styles every button, field, link and image of the page, components included; the theme guard at the end of the CSS keeps the component's buttons, fields and link colours as they are.
- The Elementor editor redraws each widget after the page has loaded: without the script below, the component stays still in the editor preview (the published page works). Add it once per site, in the footer like the component's script (`kodza/elementor-editor.js`, or a code-snippets plugin):

```js
// Kodza in the Elementor editor: the editor redraws each HTML widget after the page has loaded.
// Start Kodza in what it draws, stop it in what it replaces or removes. Once per site.
window.addEventListener('elementor/frontend/init', () => {
  if (!elementorFrontend.isEditMode()) return;
  class KodzaWidget extends elementorModules.frontend.handlers.Base {
    onInit() {
      super.onInit();
      this.kodza = [...this.$element[0].children];
      document.dispatchEvent(new CustomEvent('kodza:init', { detail: { root: this.$element[0] } }));
    }
    onDestroy() {
      super.onDestroy();
      this.kodza.forEach((root) => document.dispatchEvent(new CustomEvent('kodza:destroy', { detail: { root } })));
    }
  }
  elementorFrontend.elementsHandler.attachHandler('html', KodzaWidget);
});
```

- No child theme: everything can go in the HTML widget instead, `<style>` with the CSS, the HTML, then `<script>` with the JS. It works on the page and in the editor without the script above.

### Shopify

- Files: `assets/kodza-code-block.css` and `assets/kodza-code-block.js` (the Files commands with `-o assets/…`).
- In the section: `{{ 'kodza-code-block.css' | asset_url | stylesheet_tag }}` and `<script src="{{ 'kodza-code-block.js' | asset_url }}" defer></script>`, then the HTML.
- The theme editor re-renders sections: restart them with
  `document.addEventListener('shopify:section:load', (e) => document.dispatchEvent(new CustomEvent('kodza:init', { detail: { root: e.target } })));`
  and the same with `shopify:section:unload` → `kodza:destroy`.

### React / Next.js

- Files, side by side (e.g. in `components/kodza/`): `CodeBlock.tsx` (below), the CSS block under Code saved as `code-block.css` and the JS block as `code-block.js`, both as they are. The HTML block is already inside the component: skip it.
- Use it: `import { CodeBlock } from '@/components/kodza/CodeBlock';` then `<CodeBlock />`. Props: `variant` ("terminal", or several in an array), `vars` (the `--kz-…` variables listed under API, e.g. `vars={{ '--kz-code-bg': … }}`), `className`, `style` and the other props of its `<figure>` (`onClick`, `aria-…`).
- Next.js App Router: it is a Client Component already (`'use client'`). Pages Router: Next.js takes global CSS only in `pages/_app`, so move the `import './code-block.css'` line there.
- Safe under StrictMode, client-side navigation and prop changes: when a prop changes, the `key` gives React a fresh element, `kodza:destroy` stops the script on the old one and `kodza:init` starts it on the new one.

```tsx
'use client';
// Kodza — Code Block, for React. From https://kodza.dev/components/code-block/
// Kodza License: free to use, client work included. Not to resell or redistribute, ported or not: https://kodza.dev/docs/#print-license
// Next to this file: code-block.css and code-block.js, the component's CSS and JS from Kodza, as they are.
// Yours to edit: the markup is plain JSX below.
// The script changes this markup once React has rendered it (it adds layers, splits text, moves
// nodes), so React must not patch it afterwards. When a prop changes, the key gives React a fresh
// element: kodza:destroy stops the script on the old one, kodza:init starts it on the new one.
import { useRef, useEffect, type ComponentPropsWithoutRef, type ComponentRef, type CSSProperties } from 'react';
import './code-block.css';

type Variant = "terminal";

export type CodeBlockProps = Omit<ComponentPropsWithoutRef<'figure'>, "children" | "variant" | "vars"> & {
  /** Modifier class(es): .kodza-code--terminal */
  variant?: Variant | Variant[];
  /** Settings, as CSS variables on the root */
  vars?: {
    /** default: #0f0f0f */
    "--kz-code-bg"?: string | number;
    /** default: rgba(255, 255, 255, 0.84) */
    "--kz-code-fg"?: string | number;
    /** default: #ffffff */
    "--kz-code-bright"?: string | number;
    /** default: rgba(255, 255, 255, 0.58) */
    "--kz-code-dim"?: string | number;
    /** default: rgba(255, 255, 255, 0.09) */
    "--kz-code-line"?: string | number;
    /** default: rgba(255, 255, 255, 0.06) */
    "--kz-code-mark"?: string | number;
    /** default: none */
    "--kz-code-max-height"?: string | number;
    /** default: cubic-bezier(0.22, 1, 0.36, 1) */
    "--kz-code-ease"?: string | number;
  };
  className?: string;
};

export function CodeBlock({ variant, vars, className, style, ...rest }: CodeBlockProps) {
  const ref = useRef<ComponentRef<'figure'>>(null);
  const classes = ["kodza-code", ...([] as string[]).concat(variant ?? []).map((v) => `kodza-code--${v}`), className].filter(Boolean).join(' ');
  // Everything the markup is made of: when it changes, React gets a fresh element (see the top)
  const key = JSON.stringify([classes, vars, style, rest]);

  // Starts the script on this element once React has rendered it, stops it when it goes
  useEffect(() => {
    const root = ref.current;
    let live = true;
    // @ts-ignore: a plain script, no types to find
    import('./code-block.js').then(() => {
      if (live) document.dispatchEvent(new CustomEvent('kodza:init', { detail: { root } }));
    });
    return () => {
      live = false;
      document.dispatchEvent(new CustomEvent('kodza:destroy', { detail: { root } }));
    };
  }, [key]);

  return (
    <figure key={key} {...rest} className={classes} style={{ ...vars, ...style } as CSSProperties} ref={ref}>
      <figcaption className="kodza-code__head">
        <span className="kodza-code__file">fill-button.js</span>
        {' '}
        <button className="kodza-code__copy" type="button">
          <span className="kodza-code__words">
            <span>Copy</span>
            <span>Copied</span>
          </span>
        </button>
      </figcaption>
      <pre className="kodza-code__pre" data-lang="js" data-highlight="4-6">
        <code>{"// The ink comes in from where the pointer did\ndocument.querySelectorAll('.kodza-fill-button').forEach((button) => {\n  button.addEventListener('pointerenter', (event) => {\n    const box = button.getBoundingClientRect();\n    const x = event.clientX - box.left;\n    button.style.setProperty('--x', `${x}px`);\n  });\n});"}</code>
      </pre>
    </figure>
  );
}
```

## Code

```html
<figure class="kodza-code">
  <figcaption class="kodza-code__head">
    <span class="kodza-code__file">fill-button.js</span>
    <button class="kodza-code__copy" type="button"><span class="kodza-code__words"><span>Copy</span><span>Copied</span></span></button>
  </figcaption>
  <pre class="kodza-code__pre" data-lang="js" data-highlight="4-6"><code>// The ink comes in from where the pointer did
document.querySelectorAll('.kodza-fill-button').forEach((button) =&gt; {
  button.addEventListener('pointerenter', (event) =&gt; {
    const box = button.getBoundingClientRect();
    const x = event.clientX - box.left;
    button.style.setProperty('--x', `${x}px`);
  });
});</code></pre>
</figure>

<figure class="kodza-code kodza-code--terminal">
  <figcaption class="kodza-code__head">
    <span class="kodza-code__file">Terminal</span>
    <button class="kodza-code__copy" type="button"><span class="kodza-code__words"><span>Copy</span><span>Copied</span></span></button>
  </figcaption>
  <pre class="kodza-code__pre" data-lang="shell"><code>$ npx degit kodza/button-fill my-button
&gt; cloned kodza/button-fill#main to my-button
$ open my-button/index.html</code></pre>
</figure>
```

```css
/* Kodza License: free to use, client work included. Not to resell or redistribute, ported or not: https://kodza.dev/docs/#print-license */
/* Kodza — Code Block
   Code to read and copy: a file name, line numbers, lines to look at (data-highlight="4-6"),
   and a monochrome highlighting that works with weight and light rather than colors (keywords
   bold, comments dimmed, strings bright). Copy rolls to Copied. --terminal shows a shell: the
   prompt and the output are left out of what you copy. Languages: js, css, html, shell.
   A long file scrolls inside the block past --kz-code-max-height (none by default).
   Everything is tuned with the --kz-code-* variables. */
.kodza-code {
  --kz-code-bg: #0f0f0f;
  --kz-code-fg: rgba(255, 255, 255, 0.84);
  --kz-code-bright: #ffffff;
  --kz-code-dim: rgba(255, 255, 255, 0.58);
  --kz-code-line: rgba(255, 255, 255, 0.09);
  --kz-code-mark: rgba(255, 255, 255, 0.06);
  --kz-code-max-height: none;
  --kz-code-ease: cubic-bezier(0.22, 1, 0.36, 1);

  margin: 0;
  overflow: hidden;
  border-radius: 14px;
  background: var(--kz-code-bg);
  box-shadow: inset 0 0 0 1px var(--kz-code-line);
  color: var(--kz-code-fg);
}

.kodza-code__head {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  height: 44px;
  padding: 0 8px 0 18px;
  border-bottom: 1px solid var(--kz-code-line);
}

/* A long file name keeps to one line and ends with an ellipsis */
.kodza-code__file {
  min-width: 0;
  overflow: hidden;
  color: var(--kz-code-dim);
  font-family: "Geist Mono", ui-monospace, "SF Mono", Menlo, monospace;
  font-size: 12px;
  white-space: nowrap;
  text-overflow: ellipsis;
}

/* Copy → Copied: the words roll */
.kodza-code__copy {
  display: inline-flex;
  align-items: center;
  height: 30px;
  padding: 0 12px;
  border: 0;
  border-radius: 8px;
  background: none;
  color: var(--kz-code-fg);
  font: inherit;
  font-size: 13px;
  font-weight: 500;
  cursor: pointer;
  transition: background-color 0.2s ease, color 0.2s ease;
}

.kodza-code__copy:hover {
  background: var(--kz-code-mark);
  color: var(--kz-code-bright);
}

.kodza-code__copy:focus-visible {
  outline: 2px solid var(--kz-code-bright);
  outline-offset: 1px;
}

.kodza-code__words {
  display: inline-grid;
  overflow: hidden;
}

.kodza-code__words > span {
  grid-area: 1 / 1;
  text-align: right;
  transition: transform 0.45s var(--kz-code-ease), opacity 0.25s ease;
}

.kodza-code__words > span:nth-child(2),
.kodza-code__copy.is-copied .kodza-code__words > span:first-child {
  opacity: 0;
  transform: translateY(-110%);
}

.kodza-code__words > span:nth-child(2) {
  transform: translateY(110%);
}

.kodza-code__copy.is-copied .kodza-code__words > span:nth-child(2) {
  opacity: 1;
  transform: none;
}

/* The code */
.kodza-code__pre {
  max-height: var(--kz-code-max-height);
  margin: 0;
  padding: 16px 0;
  overflow: auto;
  font-family: "Geist Mono", ui-monospace, "SF Mono", Menlo, monospace;
  font-size: 13px;
  line-height: 1.7;
  tab-size: 2;
}

.kodza-code__pre code {
  display: block;
  min-width: max-content;
  font: inherit;
  counter-reset: kodza-code-line;
}

.kodza-code__line {
  display: block;
  padding: 0 24px 0 0;
  white-space: pre;
}

.kodza-code__line::before {
  content: counter(kodza-code-line);
  counter-increment: kodza-code-line;
  display: inline-block;
  width: 3.4em;
  padding-right: 1.4em;
  box-sizing: border-box;
  color: var(--kz-code-dim);
  text-align: right;
  opacity: 0.7;
  user-select: none;
}

/* Lines to look at: a soft band and a bar in the gutter */
.kodza-code__line.is-marked {
  background: var(--kz-code-mark);
  box-shadow: inset 2px 0 0 var(--kz-code-bright);
}

.kodza-code__line.is-marked::before {
  color: var(--kz-code-bright);
  opacity: 1;
}

/* Highlighting in weight and light */
.kodza-code__k { color: var(--kz-code-bright); font-weight: 600; }
.kodza-code__s { color: var(--kz-code-bright); }
.kodza-code__n { color: var(--kz-code-bright); }
.kodza-code__c { color: var(--kz-code-dim); }
.kodza-code__p { color: var(--kz-code-dim); }
.kodza-code__a { color: var(--kz-code-fg); font-weight: 600; }

/* Terminal: a prompt that is not copied, and quieter output */
.kodza-code--terminal .kodza-code__line::before {
  content: none;
}

.kodza-code--terminal .kodza-code__line {
  padding-left: 20px;
}

.kodza-code__prompt {
  color: var(--kz-code-dim);
  user-select: none;
}

.kodza-code__out {
  color: var(--kz-code-dim);
}

@media (prefers-reduced-motion: reduce) {
  .kodza-code__copy,
  .kodza-code__words > span {
    transition-duration: 0.01ms !important;
  }
}

/* Theming example — on a dark page, a step lighter:
.dark-section .kodza-code {
  --kz-code-bg: #161616;
  --kz-code-line: rgba(255, 255, 255, 0.12);
}
*/

/* kodza-guard 9c5286696e96 — generated by Kodza, do not edit.
   Theme guard: keeps a site's own CSS (WordPress themes, Bootstrap, CSS resets…) off this
   component. :not(#_) is always true and weighs as much as an id, so these lines win over
   theme rules made of classes and tags. Customise the component through its --kz-* variables. */

/* What the browser gives, where the component sets it only in some states: at the lowest weight, so its own rules below put it back */

:where(.kodza-code__copy):not(#_) {
  outline: revert;
  outline-offset: revert;
}

/* What the browser gives, on everything the component leaves to it */

.kodza-code:not(#_) {
  border: revert;
  padding: revert;
  outline: revert;
  text-decoration: revert;
  transition: revert;
  list-style: revert;
  box-sizing: revert;
  position: revert;
  outline-offset: revert;
  appearance: revert;
  max-height: revert;
  font-family: revert;
  font-size: revert;
  font-weight: revert;
  font-style: revert;
  line-height: revert;
  letter-spacing: revert;
  text-transform: revert;
  text-underline-offset: revert;
  text-align: revert;
  text-indent: revert;
  text-shadow: revert;
  vertical-align: revert;
}

.kodza-code__head:not(#_) {
  margin: revert;
  border-radius: revert;
  outline: revert;
  text-decoration: revert;
  transition: revert;
  list-style: revert;
  box-sizing: revert;
  float: revert;
  position: revert;
  border-top-width: revert;
  border-right-width: revert;
  border-left-width: revert;
  border-top-style: revert;
  border-right-style: revert;
  border-left-style: revert;
  border-top-color: revert;
  border-right-color: revert;
  border-left-color: revert;
  background-color: revert;
  background-image: revert;
  box-shadow: revert;
  outline-offset: revert;
  appearance: revert;
  max-width: revert;
  max-height: revert;
  color: revert;
  font-family: revert;
  font-size: revert;
  font-weight: revert;
  font-style: revert;
  line-height: revert;
  letter-spacing: revert;
  text-transform: revert;
  text-underline-offset: revert;
  text-align: revert;
  text-indent: revert;
  text-shadow: revert;
  vertical-align: revert;
}

.kodza-code__file:not(#_),
.kodza-code__words:not(#_),
.kodza-code__line:not(#_),
.kodza-code__c:not(#_),
.kodza-code__p:not(#_),
.kodza-code__s:not(#_),
.kodza-code__k:not(#_),
.kodza-code__prompt:not(#_),
.kodza-code__out:not(#_),
.kodza-code__words span:where(:not([class*="kodza-"])):not(#_),
.kodza-code__line span:where(:not([class*="kodza-"])):not(#_) {
  box-sizing: revert;
}

.kodza-code__copy:not(#_) {
  margin: revert;
  text-decoration: revert;
  list-style: revert;
  box-sizing: revert;
  float: revert;
  position: revert;
  box-shadow: revert;
  appearance: revert;
  max-width: revert;
  max-height: revert;
  letter-spacing: revert;
  text-transform: revert;
  text-underline-offset: revert;
  text-align: revert;
  text-indent: revert;
  text-shadow: revert;
  vertical-align: revert;
  white-space: revert;
  min-height: revert;
}

.kodza-code__pre:not(#_) {
  border: revert;
  border-radius: revert;
  outline: revert;
  text-decoration: revert;
  transition: revert;
  list-style: revert;
  box-sizing: revert;
  float: revert;
  position: revert;
  background-color: revert;
  background-image: revert;
  box-shadow: revert;
  outline-offset: revert;
  appearance: revert;
  max-width: revert;
  color: revert;
  font-weight: revert;
  font-style: revert;
  letter-spacing: revert;
  text-transform: revert;
  text-underline-offset: revert;
  text-align: revert;
  text-indent: revert;
  text-shadow: revert;
  vertical-align: revert;
  white-space: revert;
}

.kodza-code__pre code:where(:not([class*="kodza-"])):not(#_) {
  border: revert;
  margin: revert;
  padding: revert;
  border-radius: revert;
  outline: revert;
  text-decoration: revert;
  transition: revert;
  list-style: revert;
  box-sizing: revert;
  float: revert;
  position: revert;
  background-color: revert;
  background-image: revert;
  box-shadow: revert;
  outline-offset: revert;
  appearance: revert;
  max-width: revert;
  max-height: revert;
  color: revert;
  letter-spacing: revert;
  text-transform: revert;
  text-underline-offset: revert;
  text-align: revert;
  text-indent: revert;
  text-shadow: revert;
  vertical-align: revert;
}

.kodza-code:not(#_):where(:not([hidden])),
.kodza-code__pre:not(#_):where(:not([hidden])) {
  display: revert;
}

.kodza-code:not(#_):where([hidden]),
.kodza-code__pre:not(#_):where([hidden]) {
  display: none;
}

/* The component's own rules, one step stronger: real buttons and fields, what it sets on tags themes style (links, lists, headings, images…), and the root width (a theme may narrow it, never widen it) */

.kodza-code:not(#_) {
  border-radius: 14px;
  background: var(--kz-code-bg);
  box-shadow: inset 0 0 0 1px var(--kz-code-line);
  color: var(--kz-code-fg);
}

.kodza-code__head:not(#_) {
  display: flex;
  padding: 0 8px 0 18px;
  border-bottom: 1px solid var(--kz-code-line);
}

.kodza-code__copy:not(#_) {
  display: inline-flex;
  align-items: center;
  height: 30px;
  padding: 0 12px;
  border: 0;
  border-radius: 8px;
  background: none;
  color: var(--kz-code-fg);
  font: inherit;
  font-size: 13px;
  font-weight: 500;
  cursor: pointer;
  transition: background-color 0.2s ease, color 0.2s ease;
}

.kodza-code__copy:hover:not(#_) {
  background: var(--kz-code-mark);
  color: var(--kz-code-bright);
}

.kodza-code__copy:focus-visible:not(#_) {
  outline: 2px solid var(--kz-code-bright);
  outline-offset: 1px;
}

.kodza-code__pre:not(#_) {
  max-height: var(--kz-code-max-height);
  margin: 0;
  padding: 16px 0;
  font-family: "Geist Mono", ui-monospace, "SF Mono", Menlo, monospace;
  font-size: 13px;
  line-height: 1.7;
}

.kodza-code__pre code:not(#_) {
  display: block;
  font: inherit;
}

@media (prefers-reduced-motion: reduce) {
  .kodza-code__copy:not(#_) {
    transition-duration: 0.01ms !important;
  }
}
```

```js
// Kodza License: free to use, client work included. Not to resell or redistribute, ported or not: https://kodza.dev/docs/#print-license
// Kodza — Code Block
// Highlights the code in weight and light (js, css, html, shell; anything else stays plain),
// splits it into numbered lines, marks the lines of data-highlight, and copies it: the
// whole code, or a terminal's commands only (no prompt, no output). Copy rolls to Copied.
(() => {
  const SELECTOR = '.kodza-code';
  const RULES = {
    js: [
      ['c', /\/\/[^\n]*|\/\*[\s\S]*?\*\//y],
      ['s', /'(?:\\.|[^'\\\n])*'|"(?:\\.|[^"\\\n])*"|`(?:\\.|[^`\\])*`/y],
      ['k', /\b(?:const|let|var|function|return|if|else|for|while|of|in|new|class|extends|import|export|from|default|await|async|try|catch|throw|typeof|instanceof|this|null|undefined|true|false)\b/y],
      ['n', /\b\d+(?:\.\d+)?\b/y],
      ['p', /=>|[{}()[\];,.]/y],
    ],
    css: [
      ['c', /\/\*[\s\S]*?\*\//y],
      ['s', /'[^'\n]*'|"[^"\n]*"/y],
      ['k', /@[\w-]+/y],
      ['a', /[\w-]+(?=\s*:[^:{}]*;)/y],
      ['n', /-?\d*\.?\d+(?:px|em|rem|%|s|ms|deg|vh|vw|fr)?\b/y],
      ['p', /[{}();:,]/y],
    ],
    html: [
      ['c', /<!--[\s\S]*?-->/y],
      ['k', /<\/?[\w-]+|\/?>/y],
      ['a', /[\w:-]+(?==)/y],
      ['s', /"[^"]*"|'[^']*'/y],
    ],
  };

  // Tokens: [class or '', text]
  const tokenize = (code, lang) => {
    const rules = RULES[lang];
    if (!rules) return [['', code]];
    const out = [];
    let i = 0;
    let plain = '';
    while (i < code.length) {
      let hit = null;
      for (const [cls, re] of rules) {
        re.lastIndex = i;
        const m = re.exec(code);
        if (m && m[0]) {
          hit = [cls, m[0]];
          break;
        }
      }
      if (hit) {
        if (plain) out.push(['', plain]);
        plain = '';
        out.push(hit);
        i += hit[1].length;
      } else {
        // Words go by whole, so a keyword is never found inside a name
        const word = /[\w$-]+|[\s\S]/y;
        word.lastIndex = i;
        const chunk = word.exec(code)[0];
        plain += chunk;
        i += chunk.length;
      }
    }
    if (plain) out.push(['', plain]);
    return out;
  };

  const span = (cls, text) => {
    const el = document.createElement('span');
    if (cls) el.className = `kodza-code__${cls}`;
    el.textContent = text;
    return el;
  };

  // One instance. Everything it starts is tied to `signal`, so kodza:destroy stops it all
  function mount(root, signal) {
    const pre = root.querySelector('.kodza-code__pre');
    const code = pre?.querySelector('code');
    const copy = root.querySelector('.kodza-code__copy');
    if (!code) return;
    const source = code.textContent.replace(/\n$/, '');
    const lang = pre.dataset.lang || '';
    const marked = new Set();
    (pre.dataset.highlight || '').split(',').forEach((part) => {
      const [a, b] = part.split('-').map(Number);
      for (let n = a; n <= (b || a); n++) if (n) marked.add(n);
    });

    // Lines: a terminal shows its prompt apart and quiets the output
    const lines = [document.createElement('span')];
    if (lang === 'shell') {
      source.split('\n').forEach((text, i) => {
        if (i) lines.push(document.createElement('span'));
        const line = lines[lines.length - 1];
        if (text.startsWith('$ ')) line.append(span('prompt', '$ '), text.slice(2));
        else line.append(span('out', text));
      });
    } else {
      tokenize(source, lang).forEach(([cls, text]) => text.split('\n').forEach((piece, i) => {
        if (i) lines.push(document.createElement('span'));
        if (piece) lines[lines.length - 1].append(span(cls, piece));
      }));
    }
    lines.forEach((line, i) => {
      line.classList.add('kodza-code__line');
      if (marked.has(i + 1)) line.classList.add('is-marked');
      if (!line.childNodes.length) line.append('​');
    });
    code.replaceChildren(...lines);

    // Copy: the code, or a terminal's commands only
    const text = lang === 'shell'
      ? source.split('\n').filter((line) => line.startsWith('$ ')).map((line) => line.slice(2)).join('\n')
      : source;
    let timer = 0;
    copy?.setAttribute('aria-label', 'Copy the code');
    copy?.addEventListener('click', async () => {
      try {
        await navigator.clipboard.writeText(text);
      } catch (error) {
        const area = Object.assign(document.createElement('textarea'), { value: text });
        area.style.cssText = 'position:fixed;opacity:0';
        document.body.append(area);
        area.select();
        document.execCommand('copy');
        area.remove();
      }
      copy.classList.add('is-copied');
      copy.setAttribute('aria-label', 'Copied');
      clearTimeout(timer);
      timer = setTimeout(() => {
        copy.classList.remove('is-copied');
        copy.setAttribute('aria-label', 'Copy the code');
      }, 1800);
    }, { signal });
  }

  // Kodza lifecycle, the same in every component: `kodza:init` starts the instances inside
  // event.detail.root (the whole page by default), `kodza:destroy` stops them and puts their
  // markup back. For themes and apps that swap content without a page load.
  const instances = new WeakMap();
  const find = (scope = document) => [scope, ...scope.querySelectorAll(SELECTOR)].filter((el) => el.matches?.(SELECTOR));
  const init = (scope) => find(scope).forEach((root) => {
    if (root.classList.contains('is-ready')) return; // already running, maybe from another copy of this script
    const controller = new AbortController();
    instances.set(root, { controller, html: root.innerHTML, attrs: [...root.attributes].map((a) => [a.name, a.value]) });
    mount(root, controller.signal);
    root.classList.add('is-ready');
  });
  const destroy = (scope) => find(scope).forEach((root) => {
    const instance = instances.get(root);
    if (!instance) return;
    instances.delete(root);
    instance.controller.abort();
    [...root.attributes].forEach((a) => root.removeAttribute(a.name));
    instance.attrs.forEach(([name, value]) => root.setAttribute(name, value));
    root.innerHTML = instance.html;
  });
  document.addEventListener('kodza:init', (event) => init(event.detail?.root));
  document.addEventListener('kodza:destroy', (event) => destroy(event.detail?.root));
  init();
  // Loaded in <head>, the script runs before the markup exists: once more when it is parsed
  if (document.readyState === 'loading') document.addEventListener('DOMContentLoaded', () => init(), { once: true });
})();
```

Free to use, from Kodza (https://kodza.dev).