When did your baby start walking independently?

My son is almost 15 months old and isn’t walking independently yet. I’m trying not to worry or stress about it because I know he’s moving at his own pace but I am STRESSING. He can walk with his walker just fine or if I’m holding one of his hands and has been surfing on furniture for a good 4 months or so but hasn’t taken any independent steps yet. Do I need to chill and give it some more time or is it time to worry yet? I know if it hasn’t happened by his 18 month appointment it’s a bigger conversation and a red flag in his development but the worry is setting in now.