Extensions

Install alto/commonmark for the complete collection, or install the split package shown for one extension. Registration remains opt-in in both cases.

Present titled code blocks

Code block title turns a title in the fenced-code info string into a semantic caption.

Package: alto/commonmark-code-block-title

```php title="src/App.php"
echo 'Hello';

The regular pre and code output is wrapped in a figure with a figcaption. It can compose with a custom fenced-code renderer.

Build semantic sections

Content slicer wraps heading ranges in nested section elements without adding custom Markdown syntax.

Package: alto/commonmark-content-slicer

# Guide

## Install

The h2 and its following content become a section at the default threshold. Apply heading-level changes before relying on a particular section hierarchy.

Embed headings safely

Heading level shifts or maps heading levels after parsing.

Package: alto/commonmark-heading-level

# Included title    ->    ## Included title

Use it when a document fragment was authored for a different heading context. It can be combined with Content Slicer or Table of Contents.

Insert raw file content

Import reads a file and inserts its contents, optionally as a language-tagged code block or a selected line range.

Package: alto/commonmark-import

@import "src/Handler.php" {lines: 10-30, lang: php}

Use Import for raw text or source snippets. Use Include when the file must be parsed as Markdown, or Source when the output needs a filename, line numbers, or highlighted lines.

Compose Markdown files

Include reads a Markdown fragment and parses it into the current document.

Package: alto/commonmark-include

@include "sections/installation.md"

Use it for reusable sections and multi-file documents. Included content runs through the same configured environment, including other registered extensions.

Rewrite deployed URLs

Link rewriter changes link and image destinations after parsing.

Package: alto/commonmark-link-rewriter

[Guide](/guide)    ->    [Guide](https://docs.example.com/guide)

Rules can add a base URI, map exact URLs, apply a regular expression, or call application code. When combined, rules run in that order.

Display source files

Source renders a file in a source-code container with optional line selection, numbering, and highlighting.

Package: alto/commonmark-source

@source "src/Service.php" {lines: 10-20, numbers: true, highlight: "14"}

Use Source for documentation that must stay synchronized with real source files. It reads during conversion and does not execute the file.

Table of contents replaces an @toc marker with links to selected document headings.

Package: alto/commonmark-table-of-contents

@toc {min: 2, max: 3}

The extension also assigns IDs to headings. Apply Heading Level first if the table of contents must use transformed levels.

Present alternatives in tabs

Tabs turns @tabs, @tab, and @endtabs markers into tab buttons and panels.

Package: alto/commonmark-tabs

@tabs
@tab PHP
composer require alto/commonmark
@tab JSON
{"require":{"alto/commonmark":"*"}}
@endtabs

The output includes ARIA relationships and a click handler. Panel content is escaped text with line breaks, not recursively parsed Markdown.