How accurate is ChatWatch, and when is it wrong?

What is exact

If your history shows a session from 22:41 to 23:17, WhatsApp told your account that this contact was online at 22:41 and offline at 23:17.

• The time a contact came online and went offline, as WhatsApp reported it to your account. We store the event and the timestamp; nothing is estimated.
• Session lengths and daily totals, which are arithmetic on those events.
• Last seen history: the sequence of most-recent connections, each one a real event.

When it can look wrong, and why

Every one of these is a limit of WhatsApp's presence signal or of the linked-device model, not a fault we can engineer away. Tools that claim otherwise are claiming something that is not possible from the outside.

• WhatsApp itself lags. Presence can arrive a minute or so late, and "offline" is sometimes reported a little after the app was actually closed. The record is what WhatsApp sent, not a second-by-second camera feed.
• The contact hid their status. If they set last seen or online to Nobody, or excluded you, WhatsApp stops sending anything and the history stops. It looks like they vanished; they changed a setting.
• Your link dropped. ChatWatch records through your linked WhatsApp session. If WhatsApp logs that device out, or you unlink it, recording pauses until you relink and the dashboard tells you so. Gaps in every contact at once usually mean this.
• They were online on another device. WhatsApp reports presence for the account: WhatsApp Web on a laptop counts as online. "They were asleep, the phone was on the table" and "online at 02:10" can both be true.
• History before you added the contact does not exist. WhatsApp keeps no past presence, so nothing can recover it.

What the analytics mean

Online History and Last Seen are records. NightWatch is the same record filtered to the night hours. Chat Probability is different: it is a statistic, the rate at which two tracked contacts are online at the same moments compared with what chance would produce. A high probability is a strong overlap, which is a reason to look closer and never proof of a conversation. We say this on the feature page, in the app, and here, because it is the number people most want to over-read.

How to check it yourself

1. 01Add your own second number, or a friend who agrees, as a tracked contact.
2. 02Open and close WhatsApp on that phone a few times at known minutes.
3. 03Compare the Online History against what you did. That is the accuracy you will get for anyone whose status is visible to you.

Is ChatWatch legit?

ChatWatch launched in 2018 and was covered at the time by Business Insider, Lifehacker, Wired Italy, the Daily Post and Hindustan Times; the articles are linked below and still online. It has been online since, is a paid subscription with Stripe checkout, and has a privacy policy that describes exactly what it stores and for how long.

In 2018, shortly after launch, Apple and Google removed the mobile apps from their stores. Not for spying: the apps showed the same online and offline status that WhatsApp itself displays to every user, for the same reason. The objection was that a third party was building on WhatsApp's data. WhatsApp would rather you open its app and check for yourself than have someone else keep the record, because the checking is the traffic. ChatWatch has run as a web service since, doing exactly what it did then: recording what your own account is allowed to see, nothing a contact has hidden, and nothing from inside a conversation. This page lists every case where that data falls short.

In 2018, shortly after launch, Apple and Google removed the mobile apps from their stores, and several headlines called ChatWatch creepy. Both are worth saying plainly. Recording when someone is online makes people uneasy, and it should: that is why ChatWatch has done only that, from the web, ever since, why it records nothing a contact has hidden, and why this page lists every case where its data falls short. It does not read messages and it does not touch anyone else's phone. What it does, it does accurately, and it says so.