Why Your Screenshots Should Never Leave Your Mac

When we started building Stubble, we had a choice about how to handle screen captures. Most AI tools upload screenshots to the cloud for processing. We chose a different architecture.

Your screenshots stay on your Mac. Always.

The Problem with Uploading Screenshots

Most AI-powered productivity tools work like this: they capture your screen, upload the image to a server, process it with a vision model, and send results back.

This creates several problems:

Screenshots contain everything. A screenshot can capture passwords visible in a password manager, API keys in a terminal, financial data in a spreadsheet, personal conversations in Messages, medical information—literally anything visible on your screen at that moment.

You don’t control the images. Once a screenshot leaves your device, you’re trusting the company’s security, their policies, their employees, and every third-party vendor they use. You’re trusting that their image processing pipeline is secure. You’re trusting that “deleted after processing” actually means deleted.

Compliance becomes complex. If you work with client data, sending screenshots to a third-party cloud may violate your agreements. A screenshot of a client document is still that document—even if it’s been OCR’d into text.

How Stubble Handles Screen Captures

Stubble captures your screen too—but the images never leave your Mac.

Here’s the architecture:

1. Screenshots Stay Local

When Stubble takes a screenshot, it’s saved to a folder on your Mac. These images are processed locally and then deleted. The latest 100 images are kept for reference; older ones are pruned automatically.

Your screenshots are never uploaded anywhere. There’s no server receiving them, no cloud storage holding them, no image processing API analyzing them.

2. OCR Runs On-Device

Text extraction from screenshots uses Apple’s Vision framework, which runs entirely on your Mac’s hardware. The Neural Engine in Apple Silicon handles this efficiently—no network requests, no API calls.

This gives you the benefit of understanding what’s on your screen without any visual data leaving your device.

3. AI Processing Uses Sanitized Text

When Stubble needs AI assistance—for summarizing your day or answering questions about your work—it sends text descriptions, not images.

And before that text leaves your device, it passes through our DataSanitizer, which strips:

• JWT tokens and API keys
• AWS credentials and private keys
• Passwords and connection strings
• Credit card numbers
• Email addresses
• Bearer tokens

The AI (Gemini, via our secure proxy) receives something like “Worked on authentication module in VS Code for 2 hours, attended OAuth migration meeting” rather than a raw screenshot that might show actual credentials.

4. The Proxy Adds Another Layer

All AI requests go through the Stubble proxy (a Cloudflare Worker), not directly to Gemini. This means:

• Your API key is server-side, not embedded in the app
• Requests are authenticated with your Stubble account
• Rate limits protect against abuse
• We can switch AI providers without updating the app

What This Means for You

When you use Stubble:

• Your screenshots never leave your Mac — They’re captured, OCR’d locally, and deleted
• The AI never sees your raw screen — Only sanitized text summaries
• Secrets are stripped before transmission — Passwords, API keys, tokens are removed
• You don’t need IT approval for “another cloud screenshot tool” — Because screenshots don’t go to the cloud

The Tradeoffs

This architecture has tradeoffs:

Local OCR uses your resources. Vision framework runs on your Mac, using CPU and Neural Engine capacity. On modern Apple Silicon, this is negligible.

AI still requires network. Task summarization and chat features need connectivity to reach the AI backend. Your screenshots don’t go there, but sanitized text descriptions do.

Some features need cloud AI. Understanding natural language questions about your work, generating summaries, and creating timesheets all require AI capabilities that run in the cloud.

But for the core question—“should my raw screenshots be uploaded to someone else’s servers?”—the answer remains no.

Enterprise: Complete Isolation

For organizations that need zero external data transmission, Stubble Enterprise runs AI processing on your own infrastructure. The same architecture—local screenshots, local OCR—combined with on-premise AI means nothing leaves your network.

The Bottom Line

The key insight is that screen capture and AI processing can be decoupled. You don’t need to upload screenshots to get AI-powered insights about your work.

Stubble captures your screen locally, extracts text locally, sanitizes that text, and only then sends clean summaries for AI processing. Your visual screen content—the actual pixels, the actual images—stays on your Mac.

That’s privacy as architecture, not just policy.

Download Stubble for Mac and keep your screenshots on your device.