You should enable two-factor authentication for every account you can. This gives you an extra layer of protection if you get hacked. Some services give you code that changes everything 30 seconds, which you can manage with a password manager or authentication app. This method is more secure than SMS authentication, but some websites only use this. Here’s an easy way to manage those SMS two-factor authentication codes.
Services that use SMS codes will text you them from a shortcode number. If you have multiple services sending you these codes they will soon fill your conversation list. That’s why you should add each number to a 2FA contact.
Add every number you get a code from to this contact, and that way security codes will be confined to one contact instead of multiple contacts. Just tap on the conversation in Messages, then tap Details, tap the number, and finally tap Add to Contact. Or if you’re creating one for the first time, tap Create New Contact.