Can You See Me?

An estimated 95 percent of all commercial e-mail messages are sent in HTML or in a multipart (combined HTML and text) format. Most e-mail includes at least a single external image, even if it's the open-tracking image, a clear, one-pixel GIF image used to track whether an e-mail has been opened.

The primary reasons behind image-blocking features are to enable users to prohibit pornographic images from loading and to prevent spammers from knowing if users open their messages. Gmail, for example, states: "Gmail disables images sent to you to protect you from unknown senders, like spammers, who use images and links to verify that your email address is real."

Image Blocking by Major ISPs & E-mail Clients
Blocking IssueAOL
2000/ XP
w/o SP2
External images are blocked by defaultYesYesNoNoNoYesYesNo
User controls image-blocking settingsYesNoYesYesYesYesYesYes
User clicks link to enable message's imagesYesYesYesNoNoYesYesN/A
Images enabled if sender is in user's address book/buddy listYesNoYesNoYesYesYesYes
Images autoenabled if sender is on ISP whitelistYesN/AYesNoN/AN/AN/AN/A
Alt tags displayed when images disabledNoYesNoNoNoNoNoN/A
Preview window featured includedNoNoNoNoYesYesYesYes
Note: SP2 = Service Pack 2 upgrade for Windows XP
Source: EmailLabs, 2004


  1. Another advantage of disabling images, even on your web browser, is that it stops certain sites from accessing valuable information about your identity such as your IP address, ISP, DNS, host name, web browser, operating system, screen resolution, and many other things.

    In order to view an image to be displayed on the web browser you are using, the client (that's you) makes a call to the outside server, and the server verifies the request. In that process, the server views the information contained in the html header of the client side call, at which point, the server then sends back the requested image, and voila, your web browser displays the image.

    However, if you disable images from being displayed, then the server will not be able to obtain that information. Hence, your identity is intact . . . at least for that image. However, certain sites can just embed an element that tracks the html header information via another route.

  2. the images are not the only way to obtain information; there is no such thing as privacy when you’re online so blocking the images would cover only one tiny part of the problems.