Document Scanner
UnderKey's built-in document scanner lets you photograph passports, IDs, certificates, and insurance policies and encrypt them instantly — without the photo ever touching your camera roll. Automatic edge detection frames documents perfectly, even on cluttered desks or in poor lighting.
How it works
When you tap the scan button:
- The camera opens with a viewfinder overlay showing where to position the document.
- Edge detection highlights the document's corners in real time. On iOS, this uses Apple's built-in VisionKit framework. On Android, UnderKey uses its own on-device edge detection algorithm.
- The app automatically captures the photo when the document is in focus and all four corners are visible, or you can tap to capture manually.
- The photo is cropped, perspective-corrected, and enhanced on your device to remove shadows and improve contrast.
- The scan is encrypted immediately with AES-256 and stored in your vault. It never appears in your camera roll or photo library.
Why scan directly into the vault?
Most people photograph documents with their phone's camera app and then move them into a secure storage app later. This creates two problems:
- The photo appears in your camera roll first, where it syncs to iCloud Photos or Google Photos by default. Even if you delete it later, it may have already been backed up to the cloud.
- Apps with photo library access can see it. Any app you've granted photo access can read your ID scans while they're in your camera roll.
Scanning directly into UnderKey means the photo is encrypted before it's written to storage, and it never passes through your photo library at all.
What you can scan
The scanner works for any flat document:
- Passports (photo page, visa pages, residence permits).
- National ID cards and driver's licences (front and back).
- Certificates (birth, marriage, education, professional).
- Insurance policies and policy cards.
- Vehicle documents (registration, MOT/TÜV certificates).
- Bank statements, contracts, receipts, and warranties.
- Handwritten notes and diagrams.
For documents with multiple pages, scan each page separately and store them in the same vault.
Automatic vs manual capture
By default, the scanner captures automatically when it detects all four corners and confirms the document is in focus. If you prefer manual control — useful for damaged documents or items without clear edges — you can tap the capture button yourself.
What if you've already photographed a document?
If you have ID scans or passport photos already sitting in your camera roll, you can import them into UnderKey from your photo library or Files app. Once imported, delete the originals from your camera roll and your "Recently Deleted" album so they don't sync to the cloud.
Limits
- The scanner doesn't create searchable PDFs. It saves each scan as an encrypted image. If you need searchable text, use the OCR feature to extract and copy text from the scan.
- Multi-page documents require multiple scans. There's no automatic page-stitching. Scan each page individually.
- Very small text may not be perfectly legible. For documents with fine print, make sure the lighting is good and the document is flat.
Related features
- Offline AES-256 encryption — how scans are encrypted
- On-device OCR & expiry detection — extracting expiry dates from scans