Scanning a page is a solved problem. Every app in this category detects edges, corrects perspective and writes a PDF. The differences that matter are all downstream of one decision: does the text recognition run on your phone or on a server?
That answer decides whether the receipt with your card’s last four digits leaves the device, whether the app works in a basement with no signal, and whether the PDF can be encrypted before anyone else can read it.
The short version
- You want scanning and OCR to stay on the phone: ScanLocker — we make it, and the disclosure is deliberate.
- You already live in Google Drive: Drive’s built-in scanner.
- You need Adobe’s ecosystem: Adobe Scan.
- You want a free Microsoft tool: Microsoft Lens.
- You scan receipts weekly and want the simplest thing: Simple Scan or OpenScan.
How we judged these scanners
- Where OCR runs. On-device, or uploaded for recognition.
- What you must have first. No account, optional, or sign-in required.
- Whether the PDF can be protected. Password and encryption, done locally.
- What the free tier withholds. Watermark, page cap, or a subscription wall.
- Whether it works offline. The test that settles most of the claims above.
The comparison at a glance
| Scanner | OCR on device | Account | Encrypted PDF | Works offline |
|---|---|---|---|---|
| ScanLocker | Yes, ML Kit | None | Yes, AES-256 | Yes |
| Google Drive scan | No, Drive-side | Google account | No | No |
| Adobe Scan | Cloud-assisted | Adobe account | No | Partly |
| Microsoft Lens | Mixed | Microsoft account for extras | No | Partly |
| CamScanner | Cloud-assisted | Account for sync | Limited | Partly |
| Simple Scan / OpenScan | Yes | None | Varies | Yes |
Treat that table as a starting point, not a verdict — every row changes with each release, and the vendor’s listing is the authority.
ScanLocker — recognition, PDF assembly and encryption on the phone
We build ScanLocker, so read this as a product description.
ScanLocker uses ML Kit for on-device text recognition and embeds the result as an invisible text layer when it exports, so the PDF is searchable without the page ever being uploaded. It covers English and Hindi, with a per-file override.
The rest of the vault is local too: folders, tags, full-text search over the recognised text, an app lock with biometrics, and a password-protected backup with a newer-wins merge. PDFs get 256-bit AES encryption, added before the file leaves the app.
Honest limitations: Android only, no iOS build yet; no cloud sync, which is a feature for some people and a gap for anyone who wants the same vault on a tablet; and the OCR language list is short compared with the cloud services.
Google Drive scan — free, and it goes to Drive
Drive’s scanner is the least friction if you already store documents in Drive: point, shoot, crop, save, done. The text layer arrives because Drive processes the file, which is also the point — the document is in Google’s storage by design.
If your documents are already in Drive, this is not a new privacy decision. If they are not, it is.
Best for: people whose documents already live in Drive.
Adobe Scan — good output, an account in the middle
Adobe Scan produces clean, well-compressed PDFs and integrates with Adobe’s document services. It asks for an Adobe account, and the free plan leans on Adobe’s cloud for parts of the workflow.
The trade is the usual one: you get a polished pipeline in exchange for a copy of the document existing somewhere other than your phone.
Best for: people already paying for Adobe’s ecosystem.
Microsoft Lens — the free option with the least ceremony
Lens is free, fast and good at whiteboards and receipts. It can save locally, and it asks for a Microsoft account mainly when you want the Microsoft-side extras. The recognition is not fully local, so offline searchable PDFs are not its strength.
Best for: occasional scanning where the document is not sensitive.
CamScanner — the veteran with the widest feature set
CamScanner has been around long enough to have every feature: batch scanning, ID cards, OCR, cloud sync, sharing. The free tier is limited and the useful parts are subscription-led, and the cloud features mean documents leave the phone unless you turn them off.
Best for: people who want one app for every document workflow and will pay for it.
Simple Scan and OpenScan — small, local, unglamorous
These do one thing: capture pages into a PDF, locally, with no account. No OCR worth relying on, no vault, no search. If your need is “turn this into a PDF and email it”, that is enough.
Best for: single documents, no sensitivity, no subscription.
Which one should you install?
- The document has a card number, an ID or a medical result on it. ScanLocker — encryption should happen before storage, not after.
- You are already in an ecosystem. Drive, Adobe or Microsoft, whichever you already pay for.
- You scan once a month. Simple Scan.
- You need OCR in many languages and do not care where it runs. A cloud-assisted scanner, chosen with your eyes open.
What to check before you scan anything sensitive
- Does the app require an account? No account means no server-side identity to attach documents to.
- Turn on airplane mode and scan. If OCR still produces searchable text, recognition is local.
- Look for a password option on export. A PDF you can encrypt locally is a PDF that can travel safely.
- Read where files are saved. A visible folder you control beats an app-private store you cannot back up.
Page counts and ad surfaces are a separate question, and one that listings answer badly: what “no page limit” actually means separates the three limits that get called by one name.
We wrote about the underlying architecture in on-device OCR: searchable PDFs without a server.
How to keep this list honest
We make ScanLocker. Every scanner here changes its free tier, account rules and cloud behaviour between releases, so verify on the current Play listing before you commit — including ours. This page is reviewed when any of our apps ships a relevant change; the date above is the last review, not the publish date. Corrections: app.prodevinfotech@gmail.com.