Only the time of the open, attached to your message. No IP address, device fingerprint or location, in the spirit of Quebec's Law 25.
Most read-receipt tools rely on a third-party service that tracks the recipient's IP address and device, then sells the data. With MedLiam, the data stays on our servers.
The receipt only works if the recipient loads images. Many people block them, and MedLiam does so by default with its anti-tracker.