PixelBlock is an Gmail extension that blocks email tracking attempts used against you to detect the opening/reading of emails. PixelBlock displays a 'red eye' when it finds and blocks a tracking attempt inside of an email you're reading. Take control of your email privacy Privacy Policy: This extension does not store/save or transmit any data from gmail or your computer in absolutely any form.Note: Using PixelBlock will not interfere or prevent you from using any email tracking software on the outgoing emails you send. It just protects you from being tracked by others.