In general I would completely avoid registering any two letter top-level domians like .ai or .io. However, I have had another experience that I will share that may at times mean going against that advice in specific cases. At times it may be really valuable to register the .co domain that goes with your .com domain.
If you want to know why I think the two letter TLDs are bad, I’ve written all about that in my post What you don’t know about two letter TLDs like .io or .ai and why NOT to use them. Now, on to why I think it might be worth getting the .co domain that matches your .com domain anyway.
The weird experience as the admin of a .co domain
I am the admin for a .co domain and there is a catchall email account setup for it that I’m responsible for checking. All of the emails that aren’t addressed to a specific email inbox for the domain land in this inbox. There is also a separate company that has almost the exact same domain except theirs ends in .com instead. They operate across the world, although this isn’t really relevant except that they email things in Chinese sometimes which also isn’t really relevant it just happens to be something that I know because… well, you’ll see.
Anyway, this email account that I check for the domain I’m in charge of gets emails on a regular basis that are clearly intended for their company but people mistyped the “to” email address and ended up sending them to firstname.lastname@example.org instead of email@example.com. It actually sort of blows my mind how many of these I get. Maybe their company is large or just full of particularly poor typists?
This has the potential to be a huge security risk. Their own employees send me financial reports for their company, travel plans, meeting agendas, etc. People applying for work at their company send me resumes, copies of their IDs and more. Potential customers send me requests for sales info. I get emails from Tik Tok to ‘verify your email’ when their employees try to sign up for social media accounts. It’s really sorta weird. If I was a different sort of person I could do a lot of damage with this sort of stuff.
This experience has led me to think that if one was responsible for a large business or a business where it was important to keep correspondence secure then it would be desirable to also have the matching .co domain. At a bare minimum your emails will not be going to somebody else, but you could also get fancy and set up an auto-response to all emails letting people know that they had emailed the .co domain and not the .com or filter them or something.
However, I would not get a .co domain for anything other than for the purpose of preventing emails from a .com domain from going to somebody else. I think it’s a particularly poor choice of a TLD for using for one’s website. It’s simply too close to .com so it will always be confusing to people.
Finally, double check your spelling when you email people.