Knowledge Base

Images in email signatures – linked or embedded?

The HTML format makes it possible to add images to emails and email signatures. Graphics can be included as:

  • linked (hosted) images - online graphical resources are referenced in the email's HTML source by using a URL: <IMG src="">
  • embedded images - local graphics are added to emails as hidden attachments (referenced in the email's source via a Content-ID: <IMG src="cid:unique-content-id">).

In the table below you can learn about the advantages and disadvantages of each method.

Linked/hosted images
Downloaded directly from server
Embedded images
Included in every message
  • The email size is not increased by images - they are downloaded from a web source when an email is viewed
  • Emails with linked images are rarely blocked by antivirus software
  • You can track who received your email by analyzing web traffic for the images you linked in this message. Learn more
  • Images are displayed automatically when a message is viewed
  • Recipients are never asked by their email client to download images
  • Images are not affected by external factors (e.g. accidental deleting, image URL changes, image server accessibility, etc.)
  • Embedded images are visible when an email client works in offline mode
  • In most email clients, images are not visible until the recipient agrees to download them into the client
  • An SSL-secured server to host your graphics files is required
  • Image availability in email depends on external factors, such as accessibility of the image hosting server
  • Some filters may recognize your messages as SPAM
  • Embedded images increase the message size
  • Emails can sometimes be blocked by antivirus software
  • Embedded images are sometimes removed by mobile devices*

* Our software can automatically fix this issue for iPhones and iPads. Learn more

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