As you may have already discovered, there's a very good reason why Apple's latest operating system, El Capitan, doesn't let you use an emoji in your password.
Apple, however, doesn't have the same rule with OS X Yosemite. A user on Stack Exchange's Ask Different forum explained that he had used an emoji in his password on Yosemite – and was subsequently unable to log into his account. He originally posted about this incident last August, but it's worth repeating.
When Artiom Dashisnky created his password, he used an Emoji (at the login screen, you can press “control + Command + space” to get a window with emojis), but the Yosemite login screen doesn’t support these types of passwords after all, making it impossible for him to log in. He also had FileVault encryption enabled, which made it much harder to reset his password.
Dashisnky was eventually able to log back in, but it involved a long, complicated process. He installed and rebooted OS X onto an external hard drive, using the recovery mode, and installed the keyboard that would allow him to type the emoji password to decrypt his disk using Disk Utility. Once the drive was decrypted, a process that took a few hours, he rebooted into recovery mode and ran the terminal command “resetpassword” for his primary disk.
Only then was he able to regain access. One forum commenter pointed out that if he had “Other Input Sources” available on the login screen, he could have used Unicode Hex Input to manually enter the Emoji. This solution would only work if you had other users logged into the computer at the same time.
In theory, though, using an emoji in your password could be a good idea. A UK startup is developing a system that does just that, claiming that images like emojis are easier for users to remember. Adding more characters as an option beyond letters, numbers and symbols will make passwords harder to crack, thus making them more secure.
But let this be a lesson to Apple: Don't try to add an emoji to your password until software makers can support it.
