Markdown File Viewer od ZeeroQuani

Read Markdown in Firefox on your computer or Android phone. Markdown File Viewer automatically renders plain-text .md and .markdown web URLs as formatted documents. To read a file saved on your device, open a webpage, then choose Firefox menu > Extensions > Open Markdown file and select your file.

Features:
- Headings, lists, checklists, tables, code blocks, images, and links.
- Switch between the rendered document and original source.
- Automatic light/dark styling and a layout that fits your phone.
- Local file picker on desktop and Android, with no upload or account.
- Heading anchors and printing; relative links/images when viewing original file/web URLs.
- No analytics or remote scripts. Images and links in a document can reference external resources.

On Android, use the extension menu to open local files; selecting the extension as Android's system-wide default .md app is not supported. The file picker reads the selected file only, so nearby images/files are not available there. Heading links and absolute web addresses still work.

On desktop, files opened directly in Firefox can render automatically after enabling Access local files on your computer in the extension's Permissions and data. Website permissions are needed for automatic web rendering.

Raw HTML is shown as text. Files served as downloads, normal HTML webpages, and extensionless URLs are not converted. Requires Firefox 142 or later.