Introducing Water Reminder: Hydration Tracking That Works Offline

Water Reminder is out now on Google Play and the App Store. It does one thing: it works out how much water you should be drinking, spaces reminders across the hours you are actually awake, and keeps a record you can look back at. It does that without an account, without a server, and without sending anything anywhere.

The number everyone quotes is not a real number

Almost every hydration app starts from eight glasses a day. It is worth knowing where that figure came from, because the honest answer is that nobody is sure. The most credible trail leads to a 1945 recommendation from the US Food and Nutrition Board suggesting around 2.5 litres a day for adults. The sentence immediately after it noted that most of that quantity is already present in prepared food. The first sentence travelled; the second did not.

When a physiologist went looking for the evidence base in 2002, he could not find one. That does not mean drinking water is pointless. It means a single fixed target, applied to everyone regardless of size, activity or climate, was never founded on anything.

What the official figures actually say

Two things stand out. The official figures differ from each other by a wide margin, which tells you how soft the underlying science is. And both of them are total water, including what comes from food — typically about a fifth of the total. A target that ignores that is asking you to drink more than the guideline it claims to follow.

Reminders that fit the day you actually have

A reminder at three in the morning is worse than no reminder, because it teaches you to dismiss the app. Water Reminder asks when you wake and when you go to bed, spreads its prompts evenly between those two points, and stops before bedtime. They survive a phone restart, which sounds obvious and is a common place for reminder apps to quietly fail.

Progress you can read in a glance

The main screen is a ring that fills as you drink, changing colour through the day from "time to drink" to "goal reached". Today's log is editable, so a mis-tap does not become a permanent wrong entry. Beyond today there are seven and thirty day charts, your daily average, and a count of consecutive days you have hit your goal.

Nothing leaves your phone

The app is free and carries ads from Google AdMob. Your advertising identifier is used only if you allow tracking when the app asks, and you can change that afterwards in Settings under Privacy & Security, Tracking. On Android, the advertising ID can be reset or deleted in the system settings, usually under Privacy or Google, then Ads. A one-time purchase removes the ads permanently. The hydration log itself is not collected, because there is nowhere to collect it to.

Now on Android too

When this post first went up, the Android build was still in review and we did not link to it, because a link to a store page that does not exist yet is worse than no link. It has since cleared review: Water Reminder is on Google Play, with the same features, the same twenty languages and the same rule that nothing leaves your phone. The two versions do not sync with each other — there is no server to sync through — so if you switch phones, your history stays on the old one.

One last thing, and we would rather say it plainly than bury it: Water Reminder is not a medical device and does not replace professional advice. If you have a condition that affects how much you should drink — and several do, in both directions — talk to a healthcare professional about your own needs rather than to an app that knows your body weight and nothing else.

Frequently asked questions