Markdown Viewer Webext Autor: Cimbali

Markdown is a lightweight markup language which uses plain text to describe formatting information, such as # Heading, 1. numbered list, bold, etc. This add-on identifies markdown documents by the extension in the URL (.md, .markdown, etc.). When you navigate to a markdown document, if the content is plain text, this add-on formats it into HTML (with headings, bold text, etc.) as described in the document and displays it directly in your browser.

<strong>Features</strong>
<ul>
<li>Renders markdown files on the web <em>and</em> local files (<code>file://</code> URLs).</li>
<li>Rendering is triggered through a button in the URL bar.<br />
Automatic rendering is available optionally (requires more permissions to check pages for markdown).</li>
<li>Works securely, by rendering pages inside a sandboxed iframe.</li>
<li>Adjustable rendering style:
<ul>
<li>Out of the box dark mode support</li>
<li>Pick page styling from default or github-lookalike.</li>
<li>Pick code coloring from all highlight.js styles</li>
<li>Add your own custom CSS (in the addon preferences)</li>
</ul>
</li>
<li>Use a separate extension page to for heavy pages and environments that try to download markdown files, with
<ul>
<li>Light browser footprint, by rendering pages in a separate worker thread</li>
<li>One-time file picker confirmation, to access local files</li>
</ul>
</li>
<li>Prepending <code>ext+view-markdown:</code> to an URL opens that page in the extension for rendering.</li>
<li>Supports header anchors (i.e. links).</li>
<li>Optional markdown syntax extensions:
<ul>
<li>checkboxes,</li>
<li>footnotes,</li>
<li>fancy lists (e.g. roman numerals)</li>
<li>laTeX,</li>
<li><a href="https://mermaid.js.org/syntax/examples.html">mermaid.js</a> diagrams</li>
<li>front matters,</li>
<li>and emojis.</li>
</ul>
</li>
<li>Download rendered result as static HTML page</li>
<li>Link to page source</li>

<li>Respects website security, including <code>Content-Security-Policy</code> headers, by not automatically injecting code into such pages even when automatic rendering is enabled. Rendering can be forced manually through the URL bar button.</li>
</ul>

⚠ In order to open local files, check the "Access local files on your computer" permission in the "Permissions and data" tab of the addon's settings

⚠ On Linux and macOS, due to Firefox limitations, your browser may try to download a local markdown file instead of opening it.
Simply prepend <code>ext+view-markdown:</code> to the <code>file://</code> URL and confirm the access, or open the markdown viewer page through the toolbar button and select the desired file from a file picker.

<strong>Permissions</strong>
This add-on requires minimal permissions to do its job. There are:
<ul>
<li>Storage (<em>mandatory</em>, not shown by Firefox), to store preferences (including your personalized CSS) in your sync profile.</li>
<li>Active tab (<em>mandatory</em>, not shown by Firefox), to access a page’s URL and contents for rendering, when the URL bar button is clicked.</li>
<li>Host permissions (<em>optional</em>, presented as “access data on all websites”), to check pages whose URLs have markdown file extensions (<code>.md</code>, <code>.markdown</code>, etc.) for renderable markdown.</li>
</ul>