UnitLens User Guide
Scan food and beauty barcodes for nutrition, ingredients, and personal allergen and diet warnings, then compare unit prices to find the better value.
Table of Contents
Getting Started
How do I scan my first product?
Open the app and tap the "Scan" tab. Tap "Tap to Scan" to start the camera, then point it at a product barcode. UnitLens detects the barcode automatically and shows the product, along with any allergen or diet warnings that apply to you. Tap the product to see its full details.
Can I enter a barcode manually?
Yes. On the "Scan" tab, tap "Enter Barcode Manually". Type the number printed under the barcode. UnitLens checks the digits as you type and points out likely typos, such as the wrong number of digits or a check digit that doesn't match. Tap "Lookup Product" to find it.
What happens the first time I open the app?
A short welcome tour asks which allergens you want to avoid and whether you follow a diet. UnitLens uses your answers to flag products. You can tap "Skip" and set these up later in Settings.
How do I set up my allergen profile?
Tap the gear icon to open Settings, then tap "Manage Allergens". Tap any common allergen (Milk, Eggs, Fish, Shellfish, Tree nuts, Peanuts, Wheat, Soybeans, Sesame) to add it, or tap "Add Custom" to enter your own. To remove an allergen, swipe left on it under "Your Allergens". UnitLens warns you whenever a product contains one of your allergens.
How do I enable iCloud sync?
Go to Settings and turn on "Enable iCloud Sync". Make sure you're signed in to iCloud with the same Apple Account on each device. Your products, favorites, saved prices, and settings sync across your devices. Note: the change takes full effect after you restart the app.
Can I choose which tab opens when I launch the app?
Yes. Go to Settings > Startup > Default Tab and choose Search, Scan, or Favorites.
Can I use UnitLens on iPad?
Yes. On iPad, UnitLens uses a sidebar with Search, Scan, and Favorites, and shows product details next to your list. With a keyboard: ⌘F search products, ⌘S scan a barcode, ⌘1 show favorites, ⌘/ focus the search field, ⌃⌘S toggle the sidebar, and ⌘? show all keyboard shortcuts.
Scanning and Searching
What types of barcodes does UnitLens support?
EAN-13 (most common for food and beauty products), EAN-8 (smaller packages), UPC-A and UPC-E (common in North America), and ITF-14 (cases and multipacks).
Can I scan from my photo library?
Yes. While the scanner is running, tap "Photos" below the camera and choose an image that contains a barcode. UnitLens finds the barcode in the image and looks up the product.
Can I scan several products in a row?
Yes. While the scanner is running, tap "Batch" to turn on batch mode, then scan each barcode in turn. A counter shows how many you've collected, and you can remove one by tapping the X button next to it. Tap "Look Up Products" when you're done. If two or more products are found, UnitLens opens the first two side by side in Compare.
Does UnitLens work with beauty products?
Yes. Scan or search for cosmetics and personal care products the same way you do for food. Beauty products show their ingredients and labels, how long they last once opened (for example, "Use within 12 months of opening"), and any fragrance allergens from the EU's list of declarable allergens found in the ingredients.
Is there a faster way to start scanning?
Yes. Touch and hold the UnitLens icon on your Home Screen, then choose "Scan" or "Search" to jump straight there.
Can I search instead of scanning?
Yes. Tap the "Search" tab and type a product name, brand, or barcode. Choose "Food" or "Beauty" to search grocery or cosmetic products. Not sure what to look for? Tap "Browse Categories" to explore products by category.
Why wasn't my product found?
The product may not be in the Open Food Facts or Open Beauty Facts database yet. Check the number with "Enter Barcode Manually", or try searching for the product by name or brand on the "Search" tab.
Understanding Nutrition Data
What is Nutri-Score?
Nutri-Score is a nutrition label that rates food quality from A (best) to E (worst): A (Green) = Excellent nutritional quality, B (Light Green) = Good nutritional quality, C (Yellow) = Average nutritional quality, D (Orange) = Poor nutritional quality, E (Red) = Very poor nutritional quality. Tap the Nutri-Score badge on any product to learn how it's calculated.
What is NOVA classification?
NOVA classifies foods by their level of processing: Group 1 = Unprocessed or minimally processed foods, Group 2 = Processed culinary ingredients, Group 3 = Processed foods, Group 4 = Ultra-processed foods. Tap the NOVA badge on any product to learn more.
What is the Health Overview?
The Health Overview shows a product's key nutrients at a glance: Energy (kcal), Fat, Carbs, Protein, Sugars, and Salt. The full breakdown is in the "Nutrition Facts" section below it.
What's the difference between "per 100g" and "per serving"?
Use the selector in "Nutrition Facts" to switch views. Per 100g/ml: Standardized values for easy comparison between products. Per Serving: Values based on the manufacturer's suggested serving size, available when the product lists one.
Where can I learn more about nutrition labels?
Tap the info button next to "Health Overview" or "Nutrition Facts", or go to Settings > Understanding Nutrition. You'll find explanations of Nutri-Score, NOVA, key nutrients to watch, per 100g versus per serving, major allergens, and additives.
Why is some nutrition data missing?
Not all products have complete nutrition information in the database. Contributors add data over time, so check back later or refer to the product label. Beauty products don't show nutrition information.
Allergen Alerts
How do allergen alerts work?
Set your allergens in Settings > Manage Allergens. When a product contains one of them, a "Contains your allergens" warning names the allergens found. It appears on the scan result and at the top of the product's details, and a warning badge marks the product in search results and recent products.
What allergens can I track?
Milk, Eggs, Fish, Shellfish, Tree nuts, Peanuts, Wheat, Soybeans, Sesame, and custom allergens you add. Your allergens are checked against beauty product ingredients too.
Can I hide products that conflict with my allergens?
Yes. On the "Search" tab, tap the filter button and turn on "Hide flagged for me". Products that conflict with your allergens or diets are hidden from the results. A note shows how many were hidden, and you can tap "Show all" to see them again.
Are allergen alerts 100% accurate?
Allergen data comes from Open Food Facts and Open Beauty Facts contributors. Always verify allergen information on the actual product label. Use alerts as a helpful guide, not a substitute for reading labels.
Favorites
How do I save a product to favorites?
View any product's details. Tap the heart icon in the toolbar. The product is now saved to your Favorites. You can also swipe left on a product in search results and tap "Add to favorites".
How do I remove a product from favorites?
Go to the Favorites tab. Swipe left on the product you want to remove, tap "Remove from favorites", then confirm. You can also tap the filled heart icon on the product's details.
Can I share a product?
Yes. Open the product's details and tap the share icon in the toolbar to send a link to the product along with its name and barcode.
Can I find products from Spotlight?
Yes. Products you've viewed in UnitLens are added to Spotlight on your device. Search for a product's name and tap the UnitLens result to open it.
Comparing Products
How do I see a product's unit price?
Open the product's details and type the price from the shelf tag into the "Unit Price" section. UnitLens uses the package size to show the price per ounce (oz or fl oz) or per 100 g or 100 ml. The price is saved with the product, so you'll see the unit price in Favorites and Compare too. Tap "Clear" to remove it. The section appears when the product's package size is known.
How do I switch between ounces and grams?
Go to Settings > Units > Preferred Units. Choose "Metric (g, ml)" to see unit prices per 100 g or 100 ml, or "Imperial (oz, fl oz)" to see them per ounce. The default matches your region.
How do I compare products side-by-side?
On the Favorites tab, tap "Compare", select two products, then tap "Compare 2 products". You can also scan several products with batch mode on the "Scan" tab, and UnitLens opens the first two in Compare automatically.
What does Compare show?
Shelf price (type the price for each product), Unit price, Nutri-Score, Processing (NOVA), Open life (for beauty products), and For you (whether each product is safe for your allergens and diets). The better product in each row is marked "best". A summary at the top names the best value, or tells you when the two products use different units and can't be compared. Tap the share icon to send a text summary of the comparison.
Does UnitLens suggest healthier alternatives?
Yes, for food. When a product's Nutri-Score is below A, its details can show up to two products from the same category with a better Nutri-Score. To turn suggestions off, go to Settings > Product Suggestions and turn off "Show Healthier Alternatives".
Where can I buy a product?
Product details include a "Find this product" section with links that search for the product on Amazon and, in the US, Walmart and Kroger. Links open in your browser. Amazon links are affiliate links; see Settings > Legal > Amazon Associates Disclosure for details.
Dietary Preferences
What dietary preferences can I set?
Go to Settings to configure: Vegetarian, Vegan, Gluten Free, and Keto under "Dietary Preferences", and "Prefer Cruelty-Free" under "Cosmetics".
How are diet conflicts flagged?
Products that may not fit your diet show a "May conflict with" warning. Vegetarian, Vegan, and Gluten Free are checked against the ingredients unless the product carries a matching label. Keto flags products with more than 15 g of carbohydrates per 100 g unless they're labeled keto. For beauty products, Vegan checks for animal-derived ingredients, Gluten Free checks for wheat-derived ingredients, and "Prefer Cruelty-Free" flags products without a recognizable cruelty-free label. Treat these warnings as a guide and check the label.
Troubleshooting
The camera won't start.
If you see "Camera Unavailable", tap "Open Settings" and allow camera access for UnitLens, or go to Settings > Privacy & Security > Camera on your device. Restart the app if the camera appears frozen. Ensure no other app is using the camera.
My favorites aren't syncing.
Confirm "Enable iCloud Sync" is on in Settings. Verify you're signed in to the same Apple Account on all devices. Check your internet connection. Restart the app after turning on sync. The status line below the toggle shows whether sync is up to date. If "Sync Issues" appears, tap it to review items that haven't synced.
Barcode won't scan.
Ensure adequate lighting on the barcode. Hold the camera steady about 6 inches from the barcode. Tap "Flash" below the camera for low-light conditions. If the barcode is damaged, enter the number with "Enter Barcode Manually" or scan a photo of it with "Photos".
Sync still isn't working.
Go to Settings > Sync Diagnostics to see where your data is stored and whether it's syncing. Tap "Copy Diagnostics" and email the details to support@asymmetric.enterprises so we can see exactly what's happening on your device.
Privacy and Security
What data does UnitLens collect?
All personal data (favorites, saved prices, allergen and diet settings) is stored on your device and, if you turn on sync, in your private iCloud account. No personal information is shared with third parties. Product lookups send only the barcode or search terms to Open Food Facts and Open Beauty Facts.
Is my data secure?
All iCloud data is encrypted using Apple's enterprise-grade security. No account or login required. You maintain complete control over your information.
Can I use UnitLens offline?
Yes, core features work offline. Previously viewed products are cached, and a banner lets you know when you're offline. New scans require internet to fetch product data. Searches you make offline are queued and run automatically when you're back online.
Can I export my data?
Yes. Go to Settings > Data Management > Export Data. UnitLens creates a file with your products, favorites, and settings that you can save or share. When iCloud Drive is available, a copy is also saved there.
Data Sources
Where does the nutrition data come from?
Food data comes from Open Food Facts, a free and open database with millions of products. Beauty data comes from its sister project, Open Beauty Facts. Data is contributed by users worldwide. Licensed under the Open Database License (ODbL).
How accurate is the data?
Data quality varies by product and contributor. Popular products typically have verified, accurate data. Always cross-reference with actual product labels for critical decisions.
Where do prices come from?
From you. UnitLens calculates unit prices from the shelf prices you enter, so they always match your store. Store links search the retailer's website, but UnitLens doesn't fetch prices from retailers.