Lineform

What It Does

• Write Markdown and plain text in a native macOS document app.
• Keep work saved with native macOS autosave for existing files.
• Start in a normal untitled editor window when no document is open. File ▸ Open replaces that tab while it is still pristine, or adds the selected file as a tab beside work already in progress.
• Optionally make Lineform the default app for .md and .markdown files from its one-time invitation or Settings.
• See external edits automatically: an open document reloads when its file changes on disk, so what your tools (or agents) write shows up without reopening.
• Browse your writing in the Files sidebar — your Lineform iCloud Drive folder and any workspace folder you choose — and switch files in the same window, Apple Notes-style.
• Optionally show hidden folders in the Files sidebar (like .claude or .github) to reach Markdown that lives alongside your code.
• See Mermaid diagrams rendered natively in Read and Preview modes (Write mode shows the source); a malformed or very large diagram falls back to a labeled source block rather than blocking the window.
• Write LaTeX math inline with $…$ or \(…\) and as centered blocks with $$…$$ or \[…\], rendered natively in Read and Preview modes (Write mode shows the source); invalid math falls back to its source. Ordinary dollar amounts like "$5" are left untouched.
• Switch between Write, Read, and Preview modes.
• Preview Markdown beside the source in split view.
• Navigate documents from their headings.
• Search inside the current file with match navigation, across every file in the workspace, or jump to a file by name with ⌘K.
• Format headings, lists, links, emphasis, and inline code — set a heading level with ⌘1 to ⌘6 (⌘0 for body text), and keep bullets, numbered items, checkboxes, and quotes going with Return.
• Write tables without counting pipes: Insert Table (⌃⌘T), Tab between cells, and Reformat Table (⌃⌘R) to line the columns up in the source.
• Have a document read aloud from Edit ▸ Speech, which skips code, math, and diagrams.
• See misspellings underlined as you write, checked by macOS on your Mac — code, math, front matter, and link addresses are skipped, and nothing is autocorrected.
• Use Apple's native Writing Tools in the editor, with Markdown structure (fenced code, front matter) protected from rewrites.
• Save Markdown or plain text, print (⌘P), or export a copy as HTML, PDF, Styled PDF, or Rich Text — headings, tables, math, and diagrams included, on a clean white page at a standard document size. Exported HTML keeps your image and link paths exactly as you wrote them.
• Preview Markdown files in Finder with Space, formatted rather than shown as raw text.
• Adjust reading font, size, line height, spacing, width, theme, reading ruler, and typewriter mode — including the bundled accessibility fonts Atkinson Hyperlegible and OpenDyslexic.

Privacy

Lineform is local-first.

• No account system.

• No analytics collection by default.

• No document upload.

• Documents stay wherever you save them.

• Files remain ordinary Markdown or text files.

• No AI built in. Connect your own if you want it.

On its own, Lineform contacts the network in exactly one case: a once-a-day read of a small public announcements file on the Lineform website, which sends no identifier and can be turned off in Settings. Your document content never reaches Lineform's developer.

If you choose to connect your own AI (Lineform ▸ Connect Your AI… — Claude, ChatGPT, Google, or any OpenAI-compatible server, including one on your Mac), only the prose of a selection you choose an AI action for is sent, directly from your Mac to that provider, under your account and their terms. Nothing is sent when you connect; your API key stays in your Mac's Keychain; Disconnect deletes it.

Full Privacy and Terms of Use are published online and linked from the app's menu.

Support

For questions, bug reports, feature requests, or other help with Lineform, please use the Lineform Issues page. Include your macOS version, Lineform version, and the steps that reproduce a problem; never attach a document that contains private writing unless you are comfortable sharing it publicly.

Agent workflow

Lineform is a good place to read and review what your coding agent writes. An optional Claude Code hook can open every Markdown file your agent writes or edits; the copy-paste recipe is in docs/agent-hooks.md, verified against Claude Code v2.1.198. Combined with live reload, the file refreshes in place as the agent works.

Updates

Lineform is distributed through the Mac App Store, which handles updates. The app ships no self-update mechanism of its own.

Requirements

• macOS 14.0 or later
• Apple Silicon or Intel Mac (universal binary)

About

Lineform is built as a native macOS document app with SwiftUI, AppKit, and TextKit. V1.0 was the first public version. Version 1.7.4 (build 36) is currently live; version 1.7.5 (build 37) is waiting for App Review; version 1.8.0 (build 38) is in internal TestFlight testing.

Credits

Lineform renders Mermaid diagrams with BeautifulMermaid (MIT), a native Swift renderer.

Lineform renders LaTeX math with SwiftMath (MIT), a native Swift renderer whose bundled math fonts are under the SIL Open Font License and the GUST Font License.

Lineform bundles accessibility-focused reader fonts under the SIL Open Font License 1.1:

• Atkinson Hyperlegible, copyright 2020 Braille Institute of America, Inc.
• OpenDyslexic, copyright Abbie Gonzalez, with Reserved Font Name OpenDyslexic.

Build From Source

Open Lineform.xcodeproj in Xcode and run the Lineform scheme.

From Terminal:

xcodebuild build \
  -project Lineform.xcodeproj \
  -scheme Lineform \
  -destination 'platform=macOS'

Run the deterministic test suite serially:

xcodebuild test \
  -project Lineform.xcodeproj \
  -scheme Lineform \
  -destination 'platform=macOS' \
  -parallel-testing-enabled NO

Release notes for maintainers live in docs/release/app-store-release.md.

License

Lineform is source-available under the PolyForm Shield License 1.0.0. See LICENSE and NOTICE.