Markdown

Extensions

Extensions add trusted syntax, rendering, transformations, analysis, or resource-backed behavior to an immutable factory profile. Install only the capabilities required by the document format.

<?php
use Alto\Markdown\Extension\Footnote\FootnoteExtension;
use Alto\Markdown\Extension\Highlight\HighlightExtension;
use Alto\Markdown\Markdown;

$factory = Markdown::github()->with(
    new FootnoteExtension(),
    new HighlightExtension(),
);

Authoring syntax

  • PairedDelimiterExtension: configurable leaf delimiter pairs.
  • SmartPunctuationExtension: quotes, dashes, and ellipses.
  • HighlightExtension: highlighted inline text.
  • DescriptionListExtension: description lists.
  • FootnoteExtension: definitions and references.
  • TabsExtension: nested tab groups.
  • MentionExtension: application-resolved mentions.
  • AttributesExtension: constrained source attributes.

Documents and HTML

  • HeadingLevelExtension: project heading levels at render time.
  • ContentSlicerExtension: group heading sections.
  • HeadingPermalinkExtension: add stable heading links.
  • TableOfContentsExtension: generate a document outline.
  • DefaultAttributesExtension: add controlled HTML attributes.
  • CodeBlockTitleExtension: render code-block titles.
  • ExternalLinkExtension: mark external links.
  • LinkRewriterExtension: rewrite link destinations.

External resources

  • ImportExtension: insert escaped source code.
  • IncludeExtension: expand bounded Markdown resources.
  • SourceExtension: display source excerpts.
  • EmbedExtension: resolve allowlisted rich embeds.

Resource-backed extensions require an injected ResourceResolver; installing an extension never grants filesystem or network authority by itself. Read Security before enabling them on untrusted input.

Use Extension points to choose a public contract, Custom extension for a minimal implementation, and Compatibility before publishing an extension package.