diff --git a/README.md b/README.md
index ae3b530..00ee62e 100644
--- a/README.md
+++ b/README.md
@@ -12,22 +12,34 @@ Use $skill-installer to install https://github.com/andydixon/securityaudit-skill
 
 Restart Codex after it installs.
 
-Or paste this into Terminal:
+Or paste this into Terminal on macOS/Linux:
 
 ```bash
 curl -fsSL https://raw.githubusercontent.com/andydixon/securityaudit-skill/main/install.sh | bash
 ```
 
+Or paste this into PowerShell on Windows:
+
+```powershell
+powershell -NoProfile -ExecutionPolicy Bypass -Command "[Net.ServicePointManager]::SecurityProtocol=[Net.SecurityProtocolType]::Tls12; Invoke-RestMethod https://raw.githubusercontent.com/andydixon/securityaudit-skill/main/install.ps1 | Invoke-Expression"
+```
+
 Restart Codex after it installs.
 
 ## Claude Code install
 
-Paste this into Terminal:
+Paste this into Terminal on macOS/Linux:
 
 ```bash
 curl -fsSL https://raw.githubusercontent.com/andydixon/securityaudit-skill/main/install-claude.sh | bash
 ```
 
+Or paste this into PowerShell on Windows:
+
+```powershell
+powershell -NoProfile -ExecutionPolicy Bypass -Command "[Net.ServicePointManager]::SecurityProtocol=[Net.SecurityProtocolType]::Tls12; Invoke-RestMethod https://raw.githubusercontent.com/andydixon/securityaudit-skill/main/install-claude.ps1 | Invoke-Expression"
+```
+
 Restart Claude Code if it was already open.
 
 ## Codex usage
diff --git a/install-claude.ps1 b/install-claude.ps1
new file mode 100644
index 0000000..b389edf
--- /dev/null
+++ b/install-claude.ps1
@@ -0,0 +1,111 @@
+param(
+  [string]$RepoSlug = $(if ($env:SECURITYAUDIT_REPO) { $env:SECURITYAUDIT_REPO } else { "andydixon/securityaudit-skill" }),
+  [string]$Ref = $(if ($env:SECURITYAUDIT_REF) { $env:SECURITYAUDIT_REF } else { "main" }),
+  [string]$SkillPath = $(if ($env:SECURITYAUDIT_SKILL_PATH) { $env:SECURITYAUDIT_SKILL_PATH } else { "securityaudit" })
+)
+
+$ErrorActionPreference = "Stop"
+
+function Say {
+  param([string]$Message)
+  Write-Host $Message
+}
+
+function Fail {
+  param([string]$Message)
+  Write-Error $Message
+  exit 1
+}
+
+function Copy-ClaudeSecurityAuditSkill {
+  param([string]$SourcePath)
+
+  $skillFile = Join-Path $SourcePath "SKILL.md"
+  if (-not (Test-Path -LiteralPath $skillFile)) {
+    Fail "Could not find SKILL.md at $SourcePath"
+  }
+
+  $skillText = Get-Content -LiteralPath $skillFile -Raw
+  if ($skillText -notmatch "(?m)^name:\s*securityaudit\s*$") {
+    Fail "SKILL.md does not look like the securityaudit skill"
+  }
+
+  $claudeHome = if ($env:CLAUDE_HOME) { $env:CLAUDE_HOME } else { Join-Path $HOME ".claude" }
+  $destParent = Join-Path $claudeHome "skills"
+  $dest = Join-Path $destParent "securityaudit"
+
+  New-Item -ItemType Directory -Force -Path $destParent | Out-Null
+
+  $stage = Join-Path $destParent (".securityaudit-claude-install-" + [Guid]::NewGuid().ToString("N"))
+  $stageSkill = Join-Path $stage "securityaudit"
+  New-Item -ItemType Directory -Force -Path $stageSkill | Out-Null
+
+  Copy-Item -LiteralPath $skillFile -Destination (Join-Path $stageSkill "SKILL.md") -Force
+  foreach ($dir in @("scripts", "references", "assets")) {
+    $sourceDir = Join-Path $SourcePath $dir
+    if (Test-Path -LiteralPath $sourceDir) {
+      Copy-Item -LiteralPath $sourceDir -Destination (Join-Path $stageSkill $dir) -Recurse -Force
+    }
+  }
+
+  if (-not (Test-Path -LiteralPath (Join-Path $stageSkill "SKILL.md"))) {
+    Fail "Install staging failed"
+  }
+
+  if (Test-Path -LiteralPath $dest) {
+    $backup = "$dest.backup.$(Get-Date -Format 'yyyyMMdd-HHmmss')"
+    Say "Existing Claude securityaudit skill found. Backing it up to:"
+    Say $backup
+    Move-Item -LiteralPath $dest -Destination $backup
+  }
+
+  Move-Item -LiteralPath $stageSkill -Destination $dest
+  Remove-Item -LiteralPath $stage -Force -ErrorAction SilentlyContinue
+
+  Say ""
+  Say "Installed Claude Code securityaudit skill to:"
+  Say $dest
+  Say ""
+  Say "Restart Claude Code if it was already open, then use:"
+  Say "  /securityaudit"
+  Say "  /securityaudit --fix"
+}
+
+if ($PSScriptRoot -and (Test-Path -LiteralPath (Join-Path $PSScriptRoot $SkillPath "SKILL.md"))) {
+  Say "Installing Claude Code securityaudit skill from local checkout..."
+  Copy-ClaudeSecurityAuditSkill -SourcePath (Join-Path $PSScriptRoot $SkillPath)
+  exit 0
+}
+
+if (-not (Get-Command Expand-Archive -ErrorAction SilentlyContinue)) {
+  Fail "PowerShell Expand-Archive is required. Please use PowerShell 5 or newer."
+}
+
+[Net.ServicePointManager]::SecurityProtocol = [Net.SecurityProtocolType]::Tls12
+
+$temp = Join-Path ([IO.Path]::GetTempPath()) ("securityaudit-claude-install-" + [Guid]::NewGuid().ToString("N"))
+New-Item -ItemType Directory -Force -Path $temp | Out-Null
+
+try {
+  $archive = Join-Path $temp "repo.zip"
+  $url = "https://github.com/$RepoSlug/archive/refs/heads/$Ref.zip"
+
+  Say "Downloading Claude Code securityaudit skill from $RepoSlug ($Ref)..."
+  $client = New-Object Net.WebClient
+  $client.DownloadFile($url, $archive)
+
+  Expand-Archive -LiteralPath $archive -DestinationPath $temp -Force
+
+  $skillFile = Get-ChildItem -Path $temp -Filter "SKILL.md" -Recurse |
+    Where-Object { Split-Path -Leaf (Split-Path -Parent $_.FullName) -eq $SkillPath } |
+    Select-Object -First 1
+
+  if (-not $skillFile) {
+    Fail "Could not find $SkillPath/SKILL.md in the downloaded repo"
+  }
+
+  Copy-ClaudeSecurityAuditSkill -SourcePath (Split-Path -Parent $skillFile.FullName)
+}
+finally {
+  Remove-Item -LiteralPath $temp -Recurse -Force -ErrorAction SilentlyContinue
+}
diff --git a/install.ps1 b/install.ps1
new file mode 100644
index 0000000..282fdac
--- /dev/null
+++ b/install.ps1
@@ -0,0 +1,105 @@
+param(
+  [string]$RepoSlug = $(if ($env:SECURITYAUDIT_REPO) { $env:SECURITYAUDIT_REPO } else { "andydixon/securityaudit-skill" }),
+  [string]$Ref = $(if ($env:SECURITYAUDIT_REF) { $env:SECURITYAUDIT_REF } else { "main" }),
+  [string]$SkillPath = $(if ($env:SECURITYAUDIT_SKILL_PATH) { $env:SECURITYAUDIT_SKILL_PATH } else { "securityaudit" })
+)
+
+$ErrorActionPreference = "Stop"
+
+function Say {
+  param([string]$Message)
+  Write-Host $Message
+}
+
+function Fail {
+  param([string]$Message)
+  Write-Error $Message
+  exit 1
+}
+
+function Copy-SecurityAuditSkill {
+  param([string]$SourcePath)
+
+  $skillFile = Join-Path $SourcePath "SKILL.md"
+  if (-not (Test-Path -LiteralPath $skillFile)) {
+    Fail "Could not find SKILL.md at $SourcePath"
+  }
+
+  $skillText = Get-Content -LiteralPath $skillFile -Raw
+  if ($skillText -notmatch "(?m)^name:\s*securityaudit\s*$") {
+    Fail "SKILL.md does not look like the securityaudit skill"
+  }
+
+  $codexHome = if ($env:CODEX_HOME) { $env:CODEX_HOME } else { Join-Path $HOME ".codex" }
+  $destParent = Join-Path $codexHome "skills"
+  $dest = Join-Path $destParent "securityaudit"
+
+  New-Item -ItemType Directory -Force -Path $destParent | Out-Null
+
+  $stage = Join-Path $destParent (".securityaudit-install-" + [Guid]::NewGuid().ToString("N"))
+  $stageSkill = Join-Path $stage "securityaudit"
+  New-Item -ItemType Directory -Force -Path $stageSkill | Out-Null
+
+  Copy-Item -Path (Join-Path $SourcePath "*") -Destination $stageSkill -Recurse -Force
+
+  if (-not (Test-Path -LiteralPath (Join-Path $stageSkill "SKILL.md"))) {
+    Fail "Install staging failed"
+  }
+
+  if (Test-Path -LiteralPath $dest) {
+    $backup = "$dest.backup.$(Get-Date -Format 'yyyyMMdd-HHmmss')"
+    Say "Existing securityaudit skill found. Backing it up to:"
+    Say $backup
+    Move-Item -LiteralPath $dest -Destination $backup
+  }
+
+  Move-Item -LiteralPath $stageSkill -Destination $dest
+  Remove-Item -LiteralPath $stage -Force -ErrorAction SilentlyContinue
+
+  Say ""
+  Say "Installed securityaudit to:"
+  Say $dest
+  Say ""
+  Say "Restart Codex, then use:"
+  Say "  `$securityaudit"
+  Say "  `$securityaudit --fix"
+}
+
+if ($PSScriptRoot -and (Test-Path -LiteralPath (Join-Path $PSScriptRoot $SkillPath "SKILL.md"))) {
+  Say "Installing securityaudit from local checkout..."
+  Copy-SecurityAuditSkill -SourcePath (Join-Path $PSScriptRoot $SkillPath)
+  exit 0
+}
+
+if (-not (Get-Command Expand-Archive -ErrorAction SilentlyContinue)) {
+  Fail "PowerShell Expand-Archive is required. Please use PowerShell 5 or newer."
+}
+
+[Net.ServicePointManager]::SecurityProtocol = [Net.SecurityProtocolType]::Tls12
+
+$temp = Join-Path ([IO.Path]::GetTempPath()) ("securityaudit-install-" + [Guid]::NewGuid().ToString("N"))
+New-Item -ItemType Directory -Force -Path $temp | Out-Null
+
+try {
+  $archive = Join-Path $temp "repo.zip"
+  $url = "https://github.com/$RepoSlug/archive/refs/heads/$Ref.zip"
+
+  Say "Downloading securityaudit from $RepoSlug ($Ref)..."
+  $client = New-Object Net.WebClient
+  $client.DownloadFile($url, $archive)
+
+  Expand-Archive -LiteralPath $archive -DestinationPath $temp -Force
+
+  $skillFile = Get-ChildItem -Path $temp -Filter "SKILL.md" -Recurse |
+    Where-Object { Split-Path -Leaf (Split-Path -Parent $_.FullName) -eq $SkillPath } |
+    Select-Object -First 1
+
+  if (-not $skillFile) {
+    Fail "Could not find $SkillPath/SKILL.md in the downloaded repo"
+  }
+
+  Copy-SecurityAuditSkill -SourcePath (Split-Path -Parent $skillFile.FullName)
+}
+finally {
+  Remove-Item -LiteralPath $temp -Recurse -Force -ErrorAction SilentlyContinue
+}
diff --git a/install.sh b/install.sh
index 8deeba4..5ca318a 100755
--- a/install.sh
+++ b/install.sh
@@ -82,5 +82,5 @@ say "Installed securityaudit to:"
 say "$DEST"
 say ""
 say "Restart Codex, then use:"
-say "  securityaudit"
-say "  securityaudit --fix"
+say '  $securityaudit'
+say '  $securityaudit --fix'