Your signature is also available on the mobile. Here are the steps how to use your desktop signature on the mobile:

  1. Go to the Gmail app on your iPhone (Gmail app on Android still does not support desktop or HTML signatures)
  2. Make sure you have the Mobile Signature option unchecked in your settings. Having this on will override the Desktop Signature. So make sure it is off.
  3. Now, just send an email to yourself. You’ll see the signature in the email you receive from yourself.