But on Monday – four days after learning the Guardian intended to publish this story – Whisper rewrote its terms of service; they now explicitly permit the company to establish the broad location of people who have disabled the app’s geolocation feature.

Whisper has developed an in-house mapping tool that allows its staff to filter and search GPS data, pinpointing messages to within 500 meters of where they were sent.

via Revealed: how Whisper app tracks ‘anonymous’ users | Technology | The Guardian.

Whisper, which was recently valued at over $200m, has grown rapidly since its launch two years ago. It is among the fleet of confessional apps, such as Secret and Yik Yak, which backers say enable users to be more candid than they are on other social media platforms.