AI Apps That Detect Nail Biting: Every Option Compared
Four apps now use on-device AI to catch nail biting in real time. Here’s the honest head-to-head — including where ours loses.
By Igor Gazivoda · Founder, Stop Biting
Real-time AI nail biting detection went from one app to a real category: four products now watch for hand-to-mouth movement through a camera and interrupt the habit as it happens — Stop Biting, Hands Off, Nailed, and SmartBehavior. All four process video on-device. This page compares them directly; our per-app pages go deeper on each match-up. Disclosure: Stop Biting is our product. Every competitor claim below was verified against the vendors’ own websites in August 2026, and we’ve noted honestly where each alternative beats us.
The full comparison
All details below were verified against each vendor’s public website in August 2026. Pricing and features change — confirm before buying.
| Stop Biting | Hands Off | Nailed | SmartBehavior | |
|---|---|---|---|---|
| Platforms | Mac, Windows, web (PWA) | Mac, Windows | macOS only | iOS, Android, Windows |
| Behaviors | Nail biting | Five BFRBs (nail biting, skin picking, brow/lash pulling, nose picking listed) | Nail biting | Nail biting, skin picking, other BFRBs |
| Detection | On-device (MediaPipe/WASM) | On-device, all processing local | On-device (MediaPipe/WASM) | On-device, 100% offline |
| Price | $2.99/mo or $29/yr | €2.99/mo | $4.99 one-time | Not published on site |
| Free trial | 3 days, no card | 3 days | None listed | Not stated on site |
| Tracking | Streaks + incident history | Not listed on site | Not listed on site | Daily/weekly/monthly trends |
Why this category exists
Most nail biting is automatic — episodes start and finish below conscious awareness, which is why willpower, bitter polish, and manual habit trackers so often fail: they all require the awareness the habit bypasses. Habit Reversal Training, the best-evidenced behavioural treatment, names awareness training as its first component.
Camera-based AI detection automates exactly that component. A model watches for hand-to-mouth movement and fires an alert at the moment of occurrence, supplying awareness from outside. Every app on this page implements that same insight; they differ in platform, scope, price, and what’s built around the detector.
Stop Biting — best for nail biting at a computer
Our app, so read this row knowing that. Stop Biting runs on Mac, Windows, and — uniquely in this group as of August 2026 — in a web browser as a no-install PWA. Detection uses MediaPipe hand and face models in WebAssembly, fully on-device, with zero network requests during detection. It tracks bite-free streaks and a timestamped incident history, and pairs the detector with over 100 science-backed guides on habit reversal.
Pricing is published: $2.99/month or $29/year (~$2.42/month), with a 3-day free trial and no credit card.
Honest limits: it detects nail biting only, and there’s no native phone app — on mobile it runs as a web app, not an installed detector.
Hands Off — best for multiple BFRBs on desktop
Hands Off (handsoffapp.com) is a Mac and Windows desktop app whose site markets detection for five common body-focused repetitive behaviors — listing nail biting, skin picking, eyebrow or eyelash pulling, and nose picking. All processing is local; the site states no video is recorded, no personal data is collected, and the app is GDPR compliant. It’s €2.99/month with a 3-day trial; no annual plan is listed.
If you have several BFRBs and work at a desktop, this is the strongest option in the category. See our full Stop Biting vs Hands Off comparison.
Nailed — best one-time purchase for Mac users
Nailed (nailedapp.io) is a macOS menu bar app for $4.99, one-time. It uses the same MediaPipe-via-WebAssembly approach as Stop Biting, entirely on-device — the camera feed is processed in memory and discarded, with no servers and no analytics. When it detects biting, it flashes the screen red with an optional beep.
No free trial or tracking features are listed, and it’s Mac-only — but if you want the cheapest credible detector and dislike subscriptions, Nailed is it. See our full Stop Biting vs Nailed comparison.
SmartBehavior — best for phone-based detection
SmartBehavior (smart-behavior.com) is the only entrant with native mobile apps: iOS, Android, plus Windows via the Microsoft Store (no macOS version is listed). It detects nail biting, skin picking, and other BFRBs, claims 85% detection accuracy, runs 100% offline on-device, requires no registration, and tracks daily, weekly, and monthly trends. Pricing isn’t published on its website — check the app stores.
If most of your biting happens away from a computer, this is the option built for that. See our full Stop Biting vs SmartBehavior comparison.
How to choose
Match the app to where your habit lives, not to feature counts.
Bite mainly at a computer, want tracking and a method around the alarm: Stop Biting — and the free trial needs no card, so testing it costs nothing.
Multiple BFRBs (skin picking, brow pulling) at a desktop: Hands Off.
Mac user who wants a one-time purchase and nothing recurring: Nailed.
Bite mainly away from the computer, want it on your phone: SmartBehavior.
Whichever you pick, the mechanism is the same evidence-aligned idea: automate the awareness that habit reversal training requires and the habit itself suppresses.