You must be at least 13 years of age in order to use Snapchat.
The company, Snap Inc., which owns the app, makes this extremely clear at the top of their Terms of Service page.

A screenshot of the company’s Terms of Service page. “No one under 13 is allowed to create a Snapchat account.”
In other words, if you are 11 or 12, then legally speaking, you should not be creating a Snapchat account.
If the company finds out that someone under the age of 13 is using their service, then they will immediately terminate the account.
Why is 13 the minimum age to use Snapchat?
This age limit is not unique to Snapchat.
In fact, most social media platforms will specifically state that you must be at least 13 years old in order to use their services.
These companies did not randomly select this number.
Instead, it is mostly due to the Children’s Online Privacy Protection Act (COPPA).
The act, which came into effect in 2000, is pretty strict about how US companies should handle the privacy of children. Furthermore, violations can result in large fines.
As a result, most companies decide that it’s just not worth the risk or the hassle.
It basically adds a layer of work that isn’t really worth it.
What will happen if a child under 13 creates an account?
Technically speaking, the app’s terms of service have been broken. Therefore, it is likely that they will ban the account in question.
However, Snapchat has no way of knowing a user’s actual age. For example, a user can enter a fake date of birth when they are signing up to the app. The app does not require any proof of age.
This means that the company usually has to rely on reports from third parties.
More often than not, social media apps will err on the side of caution and immediately suspend the account in question.
If there is any suspicion that the person is under 13, they will usually just deactivate the profile until the person’s age can be verified.
“It is better to be safe than sorry,” as the saying goes.
In the past, social media companies have terminated accounts belonging to children under 13.
On Youtube, there was one example where a 12-year-old boy went viral and gained thousands of subscribers over the course of a week. However, in one of his videos, he let it slip that he was only 12 years of age.
As a result, Youtube banned the account.
When it comes to this rule, companies will usually not bend. There are no grey areas here.
This is because they do not have the processes in place to deal with COPA.
It will not matter if the child has permission from their parents. They will delete the account regardless.