Update: July 29, 2015: Download our new Browser Extension to make installing your email signature in Gmail a breeze.
If Gmail says that the email signature is too long, your signature may be over the 10,000 character limit, which is the number of characters allowed in your Gmail signature.
Use Short Links
To reduce the amount of characters, turn on short links in Profile > Settings.
Use the read more link in your disclaimer
If your signature has a long legal disclaimer, use the Read More link and link to an online version of your legal disclaimer to save on characters.
So instead of including this long disclaimer:
The information contained in this e-mail is intended only for the individual or entity to whom it is addressed. Its contents (including any attachments) are confidential and may contain privileged information. If you are not an intended recipient you must not use, disclose, disseminate, copy or print its contents. If you receive this email in error, please delete and destroy the message and notify the sender by reply email.
You could include this instead:
The information contained in this e-mail is intended only for the individual or entity to whom it is addressed. Read More.
Choose an email signature template with less characters
If you're using a design-rich email signature template, for example, the Understated or Market Me, consider changing to a different template that has less characters, like the Div Party, Neptune or Socialite.
It could be an error
If your signature is not over 10,000 characters, it can mean that there is some left over code in the Gmail Signature Editor box that needs to be deleted. You need to delete the entire email signature and start again. Please read our full support article for more help. The full article also includes a helpful video showing you exactly what to do to fix this error.
If it still won't save you will just have make it shorter. Take out a social icon or a text field, until it saves.