Markdown Viewer `v1.2.0`

A plugin that installs markdown-viewer-app automatically via pip and provides a skill to open any markdown file in a full browser UI using the mdview command.

Prerequisites

VS Code with the GitHub Copilot Chat extension installed and active.
Python (3.14 or later) with pip available on PATH. The SessionStart hook installs markdown-viewer-app automatically when Python is present.

Installation

Install via the VS Code Chat Plugin Marketplace using the dimpletz/prompts-collection marketplace source and enable the markdown-viewer plugin.

How It Works

On every session start, the plugin checks whether markdown-viewer-app is installed. If Python is available and the package is not yet installed, it runs pip install markdown-viewer-app automatically and notifies you. If Python is not available, it notifies you with instructions to install it.

Once installed, use the Markdown Viewer skill by describing a need to view a markdown file — Copilot will build and execute the correct mdview command for you.

Usage

Action	Example prompt
View a markdown file	"Open README.md in the browser"
View with a specific browser	"View CHANGELOG.md in Firefox"
View on a custom port	"Open docs/guide.md on port 5001"
View with browser and port	"Open README.md in Edge on port 5002"
Stop the server	"Stop the markdown viewer server"
Stop a server on a custom port	"Stop the markdown viewer on port 5001"

Skill

Skill	Description
Markdown Viewer	Runs `mdview <file>` to open a markdown file in a browser. Supports optional `--browser` and `-p` (port) flags. Handles server startup, error reporting, and stopping the background server.

CLI Reference (mdview)

mdview [file] [options]

Flag	Default	Description
`--browser <name-or-path>`	system default	Browser to open (`chrome`, `firefox`, `msedge`, `brave`, `opera`, `safari`, `iexplore`, or a full path)
`-p, --port <port>`	`5000`	Port for the background Flask server
`--stop`	—	Stop the background server and release the port
`--version`	—	Print the installed version and exit

Components

graph TD
    A[markdown-viewer plugin]
    A --> B[SessionStart hook<br/>com.github.copilot/hooks/hooks.json]
    A --> C[Markdown Viewer skill<br/>skills/markdown-viewer/SKILL.md]
    B --> D[install-markdown-viewer.ps1<br/>Windows]
    B --> E[install-markdown-viewer.sh<br/>Linux / macOS]
    B --> F[inject-mdview-params.ps1<br/>Windows]
    B --> G[inject-mdview-params.sh<br/>Linux / macOS]
    B --> I[check-mdview-update.ps1<br/>Windows]
    B --> J[check-mdview-update.sh<br/>Linux / macOS]
    C --> H[mdview command<br/>markdown-viewer-app]

SessionStart Hook

Three scripts run at the start of every session:

install-markdown-viewer — Checks Python availability, then checks whether markdown-viewer-app is already installed. If not installed, runs pip install markdown-viewer-app. Outputs an additionalContext message for:

Newly installed: confirms successful installation.
Python not available: notifies the user that Python is required and provides a download link.
Installation failed: notifies the user with the error and a command to troubleshoot manually.

Outputs nothing if markdown-viewer-app is already installed (to keep the context clean).

inject-mdview-params — Reads the MDVIEW_BROWSER and MDVIEW_PORT environment variables. If either is set, outputs an additionalContext table of preferred mdview parameters:

MDVIEW_BROWSER: the preferred browser. Accepts a browser name (e.g. chrome, firefox, msedge) or an absolute path to the browser executable.
MDVIEW_PORT: the preferred port number for the mdview Flask server.

Outputs nothing if neither variable is set.

check-mdview-update — Runs only when markdown-viewer-app is installed. It:

Reads the installed version via pip show markdown-viewer-app.
Runs pip list --outdated to detect whether a newer release exists on PyPI.
If a newer version is available, injects the following context:

A new version of markdown-viewer-app is available (installed: X.Y.Z, latest: A.B.C). Before executing the mdview command, notify the user that a new version is available. Offer to upgrade it and use the following pip command to upgrade: pip install --upgrade markdown-viewer-app
Exits silently if the package is up to date or not yet installed.

Markdown Viewer Skill

Invoked when you ask to view a markdown file in a browser. The skill:

Verifies mdview is on PATH.
Builds the correct command from the provided file, optional browser, and optional port.
Runs the command and captures all output.
Reports success (with server URL and stop instructions) or the full error output on failure.
Stops the background server on request (mdview --stop [-p <port>]).

Markdown Viewer v1.2.0