Snapchat does not provide any direct notifications or alerts to users when someone denies their friend request. When you send a friend request to someone on Snapchat, they have the option to either accept or ignore the request. If they choose to ignore it or deny it, you won't receive any explicit notification informing you of their decision.
How Do You Know If Someone Denied Your Snapchat Request?
However, there are a few indirect ways you might be able to infer that someone has denied your Snapchat request:

Friend Request Status: If you check the person's profile after sending the friend request, and you still see the "Add Friend" button instead of "Pending," it could indicate that they either ignored or denied your request. However, keep in mind that they might not have seen the request yet or simply haven't responded.

No Snapchat Score or Bitmoji Update: When you send a friend request, you can see the person's Snapchat score (the total number of snaps sent and received) and their Bitmoji (if they have one) on the "Add Friends" screen. If you notice that their score remains unchanged and their Bitmoji doesn't update, it might suggest they haven't added you back.

Snap Map Activity: If the person is already on your Snapchat friends list, you can sometimes determine if they have denied your request based on their Snap Map activity. If they are sharing their location with friends, you should be able to see their location on the Snap Map. If you can't see their location, it might mean they either removed you from their friends list or never added you in the first place.

It's important to remember that Snapchat's features and user interface might change over time, and the platform may introduce new functionalities. Therefore, it's always a good idea to check for any updates or changes to the app's behavior.

Keep in mind that not everyone actively uses Snapchat or checks their friend requests regularly. They might not have seen your request yet, or they might have other reasons for not accepting it immediately. If you're unsure about the status of your friend request, consider reaching out to the person through other means (if you know them personally) to confirm their decision. And remember, it's essential to respect their choice, whether they choose to accept or deny your friend request.