The Rule is 10 seconds in NFHS, NCAA Men's/Women's, and NBA/WNBA, and 5 second in FIBA. That said in the 46 years I officiated (NFHS, NCAA Men's/Women's, and FIBA) I had only one situation where the Rule came into play (an AAU Girls', which play using NCAA Women's, qualifier to the National): When my count reached 12 seconds and she was still bouncing the Ball, I put air in my whistle. No more problems after that.

MTD, Sr.

The Final Countdown (Europe, 1986) ...
 

Update:

https://abcnews.go.com/Sports/wireSt...-line-78498855

One more thing for whining HS parents to fuss about. I won’t be calling this.

One, Two, Three, Four, Five, Six, Seven, Eight, Nine, Ten ...
 

Good point. Up until this recent Giannis Antetokounmpo controversy, most fans were probably unaware of the ten second free throw rule. As a player, and a coach, I was unaware of the rule and didn't know about it until I became a basketball official.

Now they're aware, and will become even more aware if the Milwaukee Bucks make it to the finals.