lvt

name: lvt description: > Inspect running Windows application UIs using the lvt (Live Visual Tree) CLI tool. Use this skill when you need to understand a Windows app's visual tree structure, capture annotated screenshots, detect UI frameworks, or find specific UI elements for verification or interaction planning.

Inspect Windows application UI with lvt

When to use

Use lvt whenever you need to understand the visual content or structure of a running Windows application. Common scenarios:

• UI verification — confirm that a UI change was applied correctly (e.g. a button label changed, a dialog appeared)
• Finding UI elements — locate a specific control, menu item, or text field in an app's visual tree
• Screenshot capture — take an annotated screenshot of an app with element IDs overlaid
• Framework detection — determine which UI frameworks an app uses (Win32, ComCtl, XAML, WinUI 3, WPF, Chromium)
• Automated UI interaction planning — get element IDs and bounds to plan mouse clicks or keyboard input

Prerequisites

Before using lvt, ensure lvt.exe and lvt_tap_{arch}.dll are available. If they are not already on PATH or in the current directory, download and extract them automatically:

# Download the latest release zip (matching host architecture) and extract to ~/.lvt
$lvtDir = "$env:USERPROFILE\.lvt"
if (-not (Test-Path "$lvtDir\lvt.exe")) {
  New-Item -ItemType Directory -Path $lvtDir -Force | Out-Null
  $arch = if ($env:PROCESSOR_ARCHITECTURE -eq "ARM64") { "arm64" } elseif ($env:PROCESSOR_ARCHITECTURE -eq "x86") { "x86" } else { "x64" }
  $release = Invoke-RestMethod "https://api.github.com/repos/asklar/lvt/releases/latest"
  $asset = $release.assets | Where-Object { $_.name -like "lvt-*-$arch.zip" } | Select-Object -First 1
  $zip = "$env:TEMP\lvt.zip"
  Invoke-WebRequest -Uri $asset.browser_download_url -OutFile $zip
  Expand-Archive -Path $zip -DestinationPath $lvtDir -Force
  Remove-Item $zip
}
# Run lvt from the install directory
& "$lvtDir\lvt.exe" --help

Once downloaded, lvt.exe persists in ~/.lvt/ and does not need to be downloaded again.

Usage

Target an application

You must specify exactly one target. Pick the most convenient option:

# By process name (most common — omit .exe extension if you like)
lvt --name notepad

# By window title substring
lvt --title "Untitled - Notepad"

# By PID
lvt --pid 1234

# By HWND (hex)
lvt --hwnd 0x1A0B3C

Get the visual tree

# JSON output (default) — best for programmatic parsing
lvt --name notepad

# XML output — more compact, easier to read
lvt --name notepad --format xml

# Write to a file instead of stdout
lvt --name notepad --output tree.json

Capture a screenshot

# Screenshot only (no tree output)
lvt --name notepad --screenshot out.png

# Screenshot + tree output together
lvt --name notepad --screenshot out.png --dump

Screenshots are annotated with element IDs (e0, e1, …) overlaid on each element, making it easy to correlate visual positions with tree nodes.

Scope to a subtree

When the full tree is too large, scope to a specific element:

# Only show element e5 and its descendants, up to 3 levels deep
lvt --name myapp --element e5 --depth 3

Detect frameworks only

lvt --name notepad --frameworks

Interpreting the output

Element IDs

Every element gets a stable ID like e0, e1, e2, etc., assigned in depth-first order. These IDs are consistent within a single invocation — use them to:

• Reference specific elements in follow-up commands (--element e5)
• Correlate screenshot annotations with tree nodes
• Identify click targets by combining element ID with its bounds

Key element properties

JSON example

{
  "target": { "hwnd": "0x001A0B3C", "pid": 12345, "processName": "Notepad.exe" },
  "frameworks": ["win32", "winui3"],
  "root": {
    "id": "e0",
    "type": "Window",
    "framework": "win32",
    "className": "Notepad",
    "text": "Untitled - Notepad",
    "bounds": { "x": 100, "y": 100, "width": 800, "height": 600 },
    "children": [ ... ]
  }
}

XML example

<LiveVisualTree hwnd="0x001A0B3C" pid="12345" process="Notepad.exe" frameworks="win32,winui3">
  <Window id="e0" framework="win32" className="Notepad" text="Untitled - Notepad" bounds="100,100,800,600">
    <ContentPresenter id="e1" framework="winui3" bounds="108,140,784,552" />
  </Window>
</LiveVisualTree>

Recommended workflow

1. Start the target app if it isn't already running
2. Run lvt --name <app> --format xml to get a quick overview of the UI tree
3. Take a screenshot with lvt --name <app> --screenshot ui.png to see the visual layout with element IDs
4. Drill into a subtree with --element <id> --depth <n> if the tree is large
5. Use element IDs and bounds to plan any UI interactions (clicks, keyboard input)

Tips

• Use --format xml for human-readable output and --format json for programmatic parsing
• If the tree is very large, use --depth to limit traversal depth first, then drill deeper with --element
• Element IDs change between invocations if the UI structure changes — always re-query before acting on stale IDs
• The tool requires no special permissions beyond being able to read the target process (same user session)
• For XAML/WinUI 3 apps, lvt injects a helper DLL into the target — this is safe and non-destructive but means lvt_tap_{arch}.dll must be next to lvt.exe
• For WPF apps, lvt injects lvt_wpf_tap_{arch}.dll and the managed LvtWpfTap.dll — both must be next to lvt.exe
• lvt.exe must match the target process architecture (x64, x86, or ARM64) — a clear error is shown on mismatch. Use lvt-x86.exe for 32-bit WPF apps.

Chrome/Edge DOM inspection (optional one-time setup)

lvt can dump the DOM tree of web pages in Chrome and Edge. This requires a one-time setup:

$lvtDir = "$env:USERPROFILE\.lvt"

# 1. Register the native messaging host for Chrome and Edge
& "$lvtDir\plugins\chromium\lvt_chromium_host.exe" --register

# 2. Load the browser extension in Chrome or Edge:
#    - Open chrome://extensions (or edge://extensions)
#    - Enable "Developer mode"
#    - Click "Load unpacked" → select the extension folder:
Start-Process "$lvtDir\plugins\chromium\extension"

After setup, lvt --name chrome or lvt --name msedge will include the DOM tree of the active tab. If the extension is not installed, lvt still works for all other frameworks — it just won't show web content.