NFC labels for food containers: complete guide
Which tag to buy, where to stick it, how to write and read it with your iPhone, and whether it really survives the freezer. You can follow the whole thing without installing anything.
The three-week mystery block
You freeze six containers on Sunday, and three weeks later you open the freezer to find six white plastic blocks that could be lentils, could be tomato sauce, or could have been in there since last summer. No photo, the marker smeared under the frost, and opening each one to check breaks the cold chain for the rest. It's a small problem, but it repeats every week.
How this gets solved today, and where each option falls short
Before getting to NFC, it's worth being honest about what already exists. None of these three options is bad; each just fails in a different place.
Marker and packing tape
Free, you already have it in a drawer, nothing to buy.
Falls short: the tape peels off in the freezer's humidity and the marker smears or fades as it thaws. You end up rewriting it every time.
Paper sticker
Reads better than plain marker, and you can print or write it more cleanly.
Falls short: it's single-use. Emptying the container means peeling it off — it usually leaves glue behind — and sticking a new one next time.
Thermal label printer
Legible, durable labels with a clean look, no handwriting involved.
Falls short: you need the printer itself plus refill rolls of label or thermal paper. For two or three containers a week, that's a cost not everyone wants to take on.
What an NFC tag is, and why it's different
An NFC tag is a thin sticker with a tiny chip and a printed antenna inside — no battery, no visible electronics. Nothing is pre-written on it: you write to it from your phone, and because it's not ink or print, you can write to it again thousands of times. The difference from the three options above isn't that it looks nicer — it's that it doesn't get used up. Empty the container, wash it, and next time you write over the same tag without peeling or sticking anything.
Which tag to buy: NTAG213 or NTAG215
Almost every cheap rewritable NFC tag you'll find uses a chip from NXP's NTAG21x family, almost always NTAG213 or NTAG215. Both work with iPhone (from the iPhone 7 onward) with no extra hardware. The real difference between the two, per the manufacturer's own datasheet, is the memory available for writing: the NTAG213 has 144 bytes of user memory and the NTAG215 has 504 bytes.
For what you need here — a short text like "Lentils · Frozen Sep 6" — about 30-40 bytes is plenty, so the NTAG213 has more than enough room and is usually the cheaper option. The NTAG215 only pays off if you want to write longer notes (ingredients, allergens) or combine text with a link.
In durability, the two chips are equal: the manufacturer specifies 10 years of data retention and 100,000 rewrite cycles for both models. Rewriting a tag once a week, that 100,000 figure covers centuries' worth of containers.
What actually varies when you buy is the adhesive, not the chip: look for tags explicitly sold for fridge or freezer use, with a protective laminate over the printed part. A bare paper sticker can pick up moisture and peel over time; a laminated one holds up much better.
This guide deliberately has no purchase links: we don't want it to read as an ad, we want it to be useful.
Where to stick it on the lid, and why there
- On the lid, not the body of the container, so you can read it without opening it or pulling it out of the freezer stack.
- On a flat area, away from any metal. Metal blocks the antenna's field and the phone won't be able to read the chip; if your lid has a metal clasp or reinforcement, stick the tag on the plastic area farthest from it.
- Away from a hinge or clasp that flexes every time you open the container: the antenna is a very thin printed trace, and repeated bending can eventually crack it.
How to write it with your iPhone
This works the same with any NDEF-compatible NFC app you already have installed — it doesn't need to be FreshTrack.
- Open the app and look for the write option (sometimes labeled "Write" or "Write tag").
- Choose a text record (or a URL record, if you'd rather link to something instead of writing a note).
- Write what you want to remember: the contents and, if you like, the date or when it expires.
- Hold the top back of your iPhone — where the NFC antenna is, near the camera — against the tag and keep it still for a second or two, until the app confirms the write.
- To reuse the container, repeat the same process: writing overwrites the previous content, no need to erase anything first.
You need an iPhone 7 or later; that's the minimum Apple supports for reading and writing NFC tags from third-party apps.
Reading it without opening an app: background tag reading
Here is the part almost nobody knows, and it changes how you use this day to day: from the iPhone XS onward, iOS reads NFC tags without you opening anything. The app doesn't have to be open, or even running. You hold the phone near the tag, a notification appears on screen, and if you tap it, iOS opens the right app and hands it whatever was written on the tag. Apple calls this background tag reading, and its documentation puts it in exactly these words: "iPhone XS and later support background tag reading."
In the iPhone User Guide, the models that have it on out of the box are the iPhone XR, XS, XS Max, SE (2nd generation) and everything after them. Apple doesn't state an iOS version on that page; what is dated is the API property that delivers a tag read this way to the app, available from iOS 12.0.
What has to be true for the notification to show up
The general condition is that the iPhone is in use — screen on. It does not have to be unlocked for the notification to appear: if it's locked, the system asks you to unlock before it hands the data to the app. And even with the screen on, Apple lists five situations where background reading is not available:
- The iPhone has never been unlocked since it was switched on.
- An app's NFC reader session is already running: if you're scanning from an app, the system stays out of the way.
- Apple Pay Wallet is in use.
- The camera is in use.
- Airplane mode is on.
What the tag has to have written on it
This is the detail that changes what's worth writing. The system doesn't look at everything on the tag: it looks inside the NDEF message for a URI record (the one of type "U") and, if there is more than one, it takes the first. That URI has to be either a universal link belonging to an app or one of the schemes Apple supports: https web addresses, mailto, sms, tel, FaceTime and FaceTime Audio, Apple Maps and HomeKit accessory setup. An app's own custom scheme won't do.
What that means for this guide: a text record — the kind recommended above for writing "Lentils · Frozen 6 Sept" — will not make the notification appear. The tag still reads perfectly well, but you have to open an NFC app to do it. If what you want is to hold the phone near the container and have it pop up on its own, the tag has to carry a URL, not a text note.
Tapping the notification does one of two things: if the URL is a universal link for an app you have installed, iOS opens that app (or brings it to the foreground) and hands it the tag's message; if no installed app is associated with that link, it opens in Safari.
Where it doesn't work
The iPhone 7, 7 Plus, 8, 8 Plus and iPhone X don't have background tag reading. They read and write tags just as well, but you have to ask: either from an app, or by turning on the NFC Tag Reader in Control Center. For this particular use, that's the real difference between a 2017 iPhone and a 2018-or-later one.
Sources: Apple, Adding Support for Background Tag Reading (Core NFC documentation) and Models that support NFC Tag Reader (iPhone User Guide).
Does it survive the freezer? Cold and humidity
Per the manufacturer's specification, the chip operates between -25°C and +70°C (-13°F to 158°F), well past a typical home freezer's -18°C (0°F). The electronics themselves aren't the issue.
What can fail is the adhesive and printed layer if the tag wasn't made for this — hence the advice to buy one sold for fridge or freezer use with a protective laminate. And the real trouble spot isn't the cold itself, it's condensation when you pull the container out: a laminated tag handles surface droplets fine without affecting the read; what can damage it over time is water working its way under the adhesive and lifting it, so it's worth drying the lid off before putting it back if it came out very wet.
How long each type of frozen food lasts
This has nothing to do with the tag, but it's the question that comes right after you've organized the freezer, so it belongs here. At -18°C (0°F), food stays safe indefinitely; the times below are for quality, not safety. These are the official FDA times for already-cooked food, which is exactly what usually ends up in a container:
| Cooked food | Freezer |
|---|---|
| Soups, stews and sauces with vegetables or meat | 2-3 months |
| Cooked beef and beef dishes | 2-3 months |
| Cooked chicken, plain pieces | 4 months |
| Cooked chicken dishes, with sauce | 4-6 months |
| Cooked fish | 4-6 months |
| Ready-to-heat meals / already-frozen casseroles | 3-4 months |
Source: US FDA, Refrigerator & Freezer Storage Chart (March 2018, Spanish-language edition). Raw foods — meat, fish — have their own timelines, different from the ones above, which are for already-cooked dishes.
By hand, or with FreshTrack
You can do all of this by hand with any NFC app from the App Store, exactly as explained above.
We built FreshTrack because we didn't want to write the date and work out the expiry by hand every Sunday: the app writes the tag, works out how long it keeps based on the food type and where you store it, and reminds you before it expires. It's free, and it's ours.
Download FreshTrack on the App Store