How an NFC sticker logs a drink in the HydraTag app
The sticker is a shortcut: you decide the amount once, and each tap afterwards logs it. In the current app version (0.1.10), NFC sticker setup and tap logging are free. In the forthcoming release, NFC tap logging and sticker setup, reading and writing will require an active HydraTag Pro upgrade; manual logging, quick add, reminders, history and unit choice stay free. The sticker is battery-free and holds nothing but a HydraTag link. It does not sense the water level, weigh the bottle or work out how much you drank.
Set up the sticker (once)
- Open the Sticker tab and tap Set up sticker, or use Set up a sticker in Settings.
- Step 1 of 2, choose amount. Enter the water per tap, from 10 to 2,000 ml (0.4 to 67.6 fl oz). The size of the bottle the sticker is on is the usual choice. Tap Next: tap sticker.
- Step 2 of 2, tap sticker. Hold the back of your phone against the sticker and keep it there until the screen says Sticker updated and "Each tap now logs 500 ml" (or your amount). The app writes the link and reads it back to verify it.
Setup does not log a drink. Typing a new amount changes nothing until you complete the tap, and writing replaces whatever the sticker held before. If the phone does not connect, move it slowly over the sticker to find the NFC reader.
Log a drink with a tap
- With Today open: Today shows "Tap your sticker here to log a drink." Hold the phone to the sticker; the drink is saved and the usual confirmation with Undo appears.
- With the app closed or in the background: the tap opens the sticker's HydraTag link, the app opens, saves the drink and shows Today with the confirmation. Your phone must be unlocked with NFC on.
- With Log water open: the app fills in the sticker's amount and waits for you to tap Save drink, so a tap while you are editing never saves twice.
- During sticker setup: a tap is treated as setup, never as a drink.
A tap of a sticker the app does not recognise shows "Not a HydraTag sticker"; set it up from the Sticker tab first. Two reads of the same tap within a moment are saved once.
Logging an amount is not measuring it
A tap logs the fixed amount you chose. If you drank less, remove the entry in History and log the real amount from Log water, or type the real amount instead of tapping. The record is what you log; see reviewing and correcting your history.
Check what a sticker holds
On Log water or the Sticker tab, choose Read sticker amount and hold the phone to the sticker. The app shows the sticker's amount without saving a drink; tap Save drink if you want to log it.
If a tap does not work
| Check | Why |
|---|---|
| NFC is on and the phone is unlocked | Android only reads tags when the screen is unlocked and NFC is enabled. |
| The right sticker version for the surface | A Standard sticker directly on steel may not read; see Standard or On-metal. |
| Phone position | The NFC antenna is usually near the top or centre of the back; thick cases can block it. |
| Look at the app, not the sound | A phone chime is not proof a drink was saved. Check the confirmation or History. |
Current version vs forthcoming release
The Android app is free on Google Play. In the current app version (0.1.10), NFC sticker setup and tap logging are free. The published version does not yet enforce a Pro gate. In the forthcoming release, NFC tap logging and sticker setup, reading and writing will require an active HydraTag Pro upgrade; manual logging, quick add, reminders, history and unit choice stay free. Pro is verified through your upgrade, not through the sticker: compatible third-party stickers may work for Pro users, but a sticker never unlocks Pro. One free sticker will be included with the planned HydraTag Pro upgrade; the sticker is not sold separately. A tested sticker compatibility list and final placement instructions will be published before Pro opens; see compatibility and care. iPhone support is not confirmed. HydraTag Pro is coming for US$9.99 one time with one free NFC sticker included. You pay shipping; the delivery charge and applicable tax will be shown before payment. Canada and USA first. Pro purchases and sticker claims are not open yet. In the forthcoming release, NFC tap logging and sticker setup, reading and writing will require an active HydraTag Pro upgrade; manual logging, quick add, reminders, history and unit choice stay free.
HydraTag guide ยท Updated October 2, 2026