What is GroupWeight?
GroupWeight is a private, encrypted weight tracking app built for people who want the motivation of tracking together — without sacrificing the privacy of tracking alone.
Most weight tracking apps either keep your data entirely to yourself, or share it openly with a group. GroupWeight sits in between: you get the accountability and friendly competition of a leaderboard, while your actual weight figures stay completely private — encrypted in your browser and never readable by anyone else, including the people running the site.

Who is it for?
GroupWeight works well for anyone who wants to track their weight alongside others — slimming clubs, workplace wellness challenges, groups of friends, families, or sports teams cutting weight for a season. It is designed to feel inclusive rather than competitive, which is why the leaderboard shows progress rather than numbers.

How does the privacy work?
When you log your weight, it is encrypted inside your browser using a key derived from your password before anything is sent to the server. The server stores only the encrypted result — a string of scrambled characters that means nothing without your password. Nobody can read your entries: not other users, not group members, not the administrator.
The leaderboard works around this by showing only changes. Members choose to share either their weight delta (how much they have lost or gained) or a percentage of their starting weight. Either way, your actual weight — what you weigh today, what you weighed when you started — is never visible to anyone else.
You can take this a step further by switching to percentage-only sharing, which prevents even the weight change figure from being sent to the server. In that mode it is mathematically impossible for anyone to calculate your real weight from the data that exists on the server.

What can I track?
Weight is the core metric, but GroupWeight also supports a full set of body measurements — waist, neck, chest, hips, thighs, biceps, calves, and body fat percentage. BMI is calculated automatically once you enter your height. You can add a private note to any entry to record context like how you are feeling, what you ate, or anything else relevant to your journey.

Goals and progress
Set a personal target — either a goal weight or a percentage to lose — and GroupWeight shows your progress as a bar and a dashed target line on your charts. Set a target date and it counts down the days. Everything in the goals section is completely private and never shared with your group or anyone else.

Groups and leaderboards
Join a group with an invite code from your administrator. Once you are in, your progress appears on the group leaderboard alongside other members. You choose what to share — weight change or percentage lost — and the leaderboard ranks everyone accordingly. Groups can have a start date so everyone is compared from the same point, regardless of when they personally began tracking. Anonymous mode is available if members prefer to appear under a handle rather than their name.

Charts and history
Your data is displayed as a running chart with a 7-day moving average to smooth out day-to-day variation. Switch between weight, percentage loss, BMI, or any measurement. Filter by time range from one month to your full history. The target line sits on the chart so you can see at a glance how your trend is tracking against your goal.

Your data belongs to you
Because your entries are encrypted with your password, there is no server-side recovery if you lose access. GroupWeight makes it easy to export everything — your entry history as a CSV and your settings as a JSON file — so you always have a local copy. You can import these files to restore your full history and preferences on any device.

Security built in
Accounts are independent of any other login system on the site. Two-factor authentication is available using any standard authenticator app. You can review every active session from any device and revoke them individually or all at once. Passwords are hashed securely and never stored in plain text.

In short
GroupWeight gives you the support of tracking with others and the honesty of tracking for yourself — without asking you to choose between them.