PixelBlock is a Gmail extension that blocks people from tracking when you open their emails.
PixelBlock is an Gmail extension that blocks email tracking attempts used to detect when you open and read emails. PixelBlock displays a 'red eye' when it finds and blocks a tracking attempt inside of an email.
Update (April 9, 2019): improved performance
This extension does not store, save, access or transmit any data from your Gmail account or computer at all. In fact, this extension runs locally on your browser and doesn't communicate with any remote servers.