MarkLens

View Markdown documents on iOS and macOS, with a Quick Look extension for fast previews in Finder.

Features

• GitHub Flavored Markdown rendering with syntax highlighting and copy buttons for code blocks.
• LaTeX math rendering with KaTeX and Mermaid diagram rendering for fenced code blocks.
• Raw Markdown editing with toolbar shortcuts, search, and synchronized preview/source scrolling.
• Local links and images, source-line links, plus wiki-style links and in-app wiki navigation on macOS.
• Native macOS document tabs, with Command-click or a link’s context menu to open a local Markdown file in a new tab.
• Browse local Markdown and wiki links in the current window, with a per-file toggle and a configurable default in Files & Folders settings.
• Choose whether linked documents follow macOS window preferences or open in a new window or tab by default.
• Customizable preview typography, content width, and CSS on macOS.
• PDF and portable HTML export bundling app resources and local images on macOS, plus direct paginated review in Preview; remote content remains linked.
• Printing and page setup on macOS.
• Quick Look previews in Finder.

Source-line links on macOS

Use a line number after a local Markdown filename to open that file at its source line:

[Details](notes.md:12)
[Nested file](folder/notes.md:27)

Blank source lines lead to the next rendered content; a line after the last content leads to the end of the page. Other apps can use marklens://open?file=<encoded-file-URL>&line=12 to open an absolute local Markdown file at a line.

For a ready-made manual check, open line-link-source.md in MarkLens and follow its links to the adjacent target file.

Requirements

Development requires Xcode 26 running on a compatible version of macOS.

MarkLens supports:

• macOS 15.6 or later
• iOS 17.6 or later

Build

Open the project:

open MarkLens.xcodeproj

Build the app from the command line:

xcodebuild -project MarkLens.xcodeproj -scheme MarkLens -configuration Debug build

Build the Quick Look extension:

xcodebuild -project MarkLens.xcodeproj -scheme QuickLookPreview_macOS -configuration Debug build

Test

Run the Markdown pipeline tests on any supported Swift development platform:

swift test --package-path MarkdownPipeline

Run the app unit and UI tests on macOS:

xcodebuild -project MarkLens.xcodeproj -scheme MarkLens -destination 'platform=macOS' test

Project Layout

• MarkLens/ contains the SwiftUI app and app-specific web resources.
• QuickLookPreview_macOS/ contains the macOS Quick Look extension.
• MarkdownPipeline/ contains the shared Markdown renderer, bundled web assets, and pipeline tests.
• Shared/ contains Swift code shared by the app and extension.
• MarkLensTests/ and MarkLensUITests/ contain app integration and UI tests.

Future Tasks

• Consider adding a custom print panel accessory for header/footer toggles and margin presets.

License

MIT. See LICENSE.

Third-Party Notices

See THIRD_PARTY_NOTICES.