MD Viewer for Windows#

A native Markdown reader and editor for Windows 10/11 — no browser engine, no .NET install,
no CDN, no telemetry. One self-contained mdview.exe that lays out and paints Markdown itself.

📥 Download for Windows — installer 34.8 MB · portable exe 50 MB

Read this in: English · Русский

What it is#

A Markdown viewer that behaves like a native Windows application, because it is one: a WinForms
shell over a hand-written Markdown engine and a hand-written layout/paint pipeline, both drawing
through GDI+.

Most "Markdown viewers" are a browser in a trench coat. This one measures every glyph itself, so
it starts in well under a second, uses no RAM beyond its own layout, and renders identically in
light and dark mode without a single web asset.

Requirements#

• Windows 10 1809+ or Windows 11 (x64).

• Nothing else. The shipped mdview.exe is self-contained: no .NET runtime, no WebView2, no
  Visual C++ redistributable, no fonts to install (it uses Segoe UI / Consolas / Cambria, which
  ship with Windows).

That matters because Windows itself carries only .NET Framework 4.8 — it does not include
.NET 8, 10 or 11, and .NET 11 is still a release candidate. A runtime-dependent build would not
start on a clean machine; this one carries its own runtime: of the 52.5 MB file, roughly 50 MB is
that runtime and 74 KB is the application itself (src/MdViewer.App/bin/.../mdview.exe).

Quick start#

Install (recommended): run MD.Viewer-1.3.0-setup.exe — it puts the viewer into
C:\Program Files\Deynekin\MD.Viewer, adds it to Installed apps, offers shortcuts for the Start
menu, desktop, Quick Launch and Favorites, and registers .md. Details and silent switches:
docs/INSTALLER.md.

Portable: mdview.exe next to your documents, no installation at all.

# open a file
.\mdview.exe notes.md

# open it in the editor, dark, zoomed to 125 %, scrolled to line 40
.\mdview.exe notes.md --mode editor --theme dark --zoom 1.25 --line 40

# export a standalone HTML next to the source
.\mdview.exe notes.md --export html

# print the rendered document (dialog, choose "Microsoft Print to PDF")
.\mdview.exe notes.md --print

Launching with no arguments restores the previous session (up to 8 tabs); --no-session starts
empty. Dragging .md files onto the window opens them in new tabs.

View modes#

Ctrl+Shift+M cycles through the three. In editor mode Ctrl+Shift+P splits the window into
editor + live preview; the preview re-renders 220 ms after you stop typing.

Files always open rendered; the last mode is not restored on start-up. If you would rather come
back to the mode you left, switch on View → Remember the last view mode (or pass --mode).

The theme button (and Ctrl+Shift+L) flips light ↔ dark in one click — it never walks through a
state that looks the same as the current one. View → Theme → Follow Windows puts it back under
system control, and the button then carries a dot to show that.

Markdown support#

CommonMark core plus the GFM and MD.Scribe extensions. The full matrix, including what degrades
gracefully, is in docs/MARKDOWN.md.

• Headings (ATX/setext, {#id}, numbering), emphasis, strike, mark, sub/superscript, code spans

• Fenced code with title="…", indented code, language-aware highlighting for ~20 language
  families, copy button per block

• Tables with per-column alignment

• Lists: nested, ordered with start values, task lists with checkboxes

• Block quotes, GitHub alerts (> [!NOTE] … > [!CAUTION]), definition lists

• Footnotes (reference and inline), [TOC], YAML front matter, emoji shortcodes

• Math: $inline$ and $$display$$ through a TeX-subset typesetter

• Mermaid drawn natively — flowchart/graph, sequenceDiagram, pie, classDiagram,
  stateDiagram-v2, gantt and journey; unsupported types fall back to a readable source card
  with a diagnostic

• Images resolved relative to the document, captions from alt text, graceful placeholder when a
  file is missing, click to open in the default viewer; links to other .md files open in a new tab

• Two-column tables double as a glossary: hovering a term in the body shows its definition

• Optional typographic replacements (--, ---, ...) and a switch for single-newline breaks

Raw HTML in a document is never executed — it is shown as source in a labelled card. That is
a security decision, not a missing feature.

Command line#

mdview [file.md] [options]

Exit codes: 0 success, 2 bad arguments or missing input.

Keyboard#

Ctrl+O open · Ctrl+S save · Ctrl+Shift+S save as · F5 reload
Ctrl+R rendered · Ctrl+U source · Ctrl+E editor · Ctrl+Shift+M cycle
Ctrl+F find · F3 find again · Esc close find
Ctrl+W close tab · Ctrl+T new tab · Ctrl+Tab next tab
Ctrl+plus / Ctrl+minus / Ctrl+0 zoom · Ctrl+Shift+L theme
Ctrl+\ outline · Ctrl+Shift+P editor preview · Ctrl+P print · F1 shortcuts

Design notes#

The interface is a deliberately small design system rather than a pile of default controls:
an 8-pt spacing rhythm, one accent colour, two neutral scales, a 32 px toolbar, a reading sheet
with real margins, and a type scale that keeps the measure between 60 and 85 characters.
Every colour pair that carries text is checked for WCAG contrast in the test suite, so a palette
tweak cannot silently make a label unreadable.

Details, tokens and the reasoning: docs/DESIGN.md.

C# 15#

The app targets net11.0-windows and is written in C# 15. Three of its features are used for
real, not for show:

• Union types — FrontMatterValue is a union of string, IReadOnlyList<string>, bool and
  long; front-matter parsing and rendering switch over it exhaustively.

• Closed hierarchies — the Markdown AST roots (Block, Inline) are closed, so every
  switch in the renderer and the HTML exporter is compiler-checked for exhaustiveness.

• Collection-expression arguments — hot lists are created as
  List<Block> output = [with(capacity: blocks.Length + 2)]; instead of a separate allocation call.

Build from source#

# .NET 11 SDK (C# 15) required — see docs/BUILD.md for the exact version and the
# two environment quirks this workspace has.
pwsh -File build/build.ps1 -Task test      # build + 146 checks
pwsh -File build/build.ps1 -Task publish   # artifacts/publish/mdview.exe (self-contained)

Project layout:

src/MdViewer.Core     Markdown parser, AST, highlighter, Mermaid parser, exporters
src/MdViewer.Render   Theme tokens, text shaping, layout, painting
src/MdViewer.App      WinForms shell: window, views, editor, chrome, CLI
src/MdViewer.Tests    Headless test runner + snapshot and UI smoke tools
docs/                 Architecture, Markdown matrix, CLI, design, testing, build
samples/              Feature tour and a Russian typography sample

What it deliberately does not do#

• No network access at all. No update checks, no telemetry, no remote images, no CDN fonts.
  A remote image is reported as "not loaded (offline viewer)" instead of being fetched.

• No HTML/JavaScript execution. Documents cannot run code inside the viewer.

• No plugin system. The feature set is the feature set.

• Mermaid covers seven diagram types. erDiagram, gitGraph, mindmap, timeline,
  quadrantChart, sankey, xychart, C4 and block show their source with a clear note; a
  diagram that cannot be parsed never breaks the page.

• Math is a TeX subset, not LaTeX: fractions, roots, sums, Greek letters, sub/superscripts.
  Unknown commands render as literal text rather than an error.

Author#

Mikhail Deynekin — Deynekin.com · github.com/paulmann · Mikhail@Deynekin.com

License#

PolyForm Noncommercial License 1.0.0 — see LICENSE.