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This is the complete hands-on walkthrough: install the agent, turn on protection, and confirm it catches sensitive data before it ever reaches an AI tool. No command line, no security background — if you can install a Mac app, you can do this.
What you’re testing. Shadow AI runs on your Mac and inspects the traffic going to AI tools (Claude, ChatGPT, and others) on your device, before anything is sent. When it sees a secret or sensitive data, it blocks or masks it. It’s the real product, so it inspects your system-wide AI traffic while it’s on — and it’s fully reversible (turn it off, or uninstall, any time).

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Before you start

A Mac on macOS 12 or newer

A PromptGuard account

Any plan works — personal Shadow AI is included with every plan. Don’t have an account? Sign up free at app.promptguard.co.
You’ll need about 15 minutes and your account password once (to approve the secure-inspection certificate — more on that below).

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Step 1 — Install

1

Download the app

Go to promptguard.co/download and click Download for macOS. It’s a signed, notarized Apple build (PromptGuard.Shadow_<version>_universal.dmg), so macOS opens it without warnings.
2

Drag to Applications

Double-click the .dmg, then drag PromptGuard Shadow into your Applications folder.
3

Launch it

Open PromptGuard Shadow from Applications. A shield icon appears in your menu bar (top-right of the screen) — that’s the whole app. Click it to open the popover.

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Step 2 — Sign in

1

Connect this device

Click the menu-bar shield, then Connect this device. Your browser opens to the PromptGuard sign-in page.
2

Sign in with your account

Log in with your PromptGuard account (or create one on the spot). The browser hands you back to the app automatically — nothing to copy or paste.

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Step 3 — Turn on protection

1

Click “Turn on protection”

In the shield popover, click Turn on protection.
2

Approve the certificate — once

macOS will ask you to approve a secure-inspection certificate and prompt for your Mac password. This is expected and required: it’s how the agent reads encrypted AI traffic to inspect it. Every tool of this kind (corporate VPNs, DLP) asks for it. You’ll only be asked once.
This certificate lets the agent inspect only the AI tools it monitors (Claude, ChatGPT, etc.) — everything else on your Mac is untouched. Uninstalling removes the certificate completely.
3

Confirm it's on

The popover should now read “You’re protected.” Leave it running in the background and go use Claude as you normally would.

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Step 4 — Try to leak a secret (the fun part)

This is what you’re really here to test. Open claude.ai and paste each of these into a new chat, one at a time. Watch what happens.
Try your own realistic examples too — a fake password, a customer email, a snippet of code with a hard-coded token. The more real-world prompts you throw at it, the more useful your feedback.

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Step 5 — See every decision

Click the menu-bar shield → Activity. You’ll see a live log of every inspected request: what tool it was going to, the decision (allowed / redacted / blocked), why, and a masked preview (the raw secret is never stored or shown). This is the audit trail an admin would see across a whole fleet.

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What good looks like

  • Safe prompts pass through instantly — you shouldn’t feel the agent.
  • Secrets (API keys, tokens, passwords) get blocked; PII (phones, emails) gets redacted.
  • The Activity log shows each catch with a clear reason.
  • Claude keeps working normally the whole time.

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Giving feedback

We want the rough edges. As you test, please note and send back:

False negatives

Something sensitive that got through un-caught. The most valuable feedback — tell us exactly what you typed and where.

False positives

A safe prompt that got blocked or mangled when it shouldn’t have been.

Friction

Anything confusing, slow, or annoying — install, sign-in, the cert prompt, the popover, performance.

Breakage

Any AI tool or website that stopped working, or connectivity issues while protection was on.
Send it to support@promptguard.co — a screenshot of the Activity row (which is already masked, so it’s safe to share) plus what you typed is perfect.

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Turning it off & uninstalling

You’re always in control:
1

Pause anytime

Click the shield → Turn off protection. AI traffic flows normally again; the app stays installed.
2

Remove completely

Shield → Uninstall (or the app’s menu). This clears the system proxy on every network, removes the inspection certificate, and deletes local data — leaving nothing behind. Then drag the app to the Trash.

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Good to know

No. The agent only inspects traffic to the AI tools it monitors; everything else — email, Slack, streaming, your VPN — goes straight through untouched. Safe AI prompts pass instantly.
If you turned on protection while a tab was mid-load, refresh the tab. If a warning persists on an AI site, that’s worth reporting — include the site.
A few tools use a newer transport (HTTP/3 over QUIC) that can route around the proxy; the browser falls back automatically, but you may see a brief hiccup. See Known Limitations for the mitigation. Report it if a site is unusable.
Prompt contents are inspected on your device. Only a masked preview (never the raw secret) is stored locally for the Activity log. See Privacy & data handling.

Hit a wall?

The troubleshooting guide covers the common install and connectivity issues — or just email support@promptguard.co and we’ll jump on it.