Had anyone used this with extensions?

Hello and thank you for your question! This is a reconstructor that fills in the "potholes" that are left when minerals are removed from the hair. For this reason, although it won't hurt extensions, it won't be extremely beneficial either. We recommend the Color Lock Masque for extensions. Thank you!

Is this safe to use on blondes with toner in them? Will it pull the toner out?

This keeps my pure Platinum Blonde (which I did myself, and we all know the struggle to get and keep that tone is real!) soft, shiny and healthy. Platinum can't be flat... it should shine like a diamond!💎💕 Don't worry about your toner . This has a low-pH that keeps your scalp and hair healthy. I also love their Malibu Blondes Crystals. Used every few weeks to remove hard water, minerals and pollution. Plus, using a purple shampoo/conditioner once a week can cause buildup that is removed along with that from other styling products. It keeps it looking freshly toned. It's vegan, safe and a wonder product. You can get each of them in a set for $7, but if you only choose one, I'd pick this one for the rebuilding of bonds, replenishment of moisture and shimmering sheen it imparts.

Directions say you can use under heat, has anyone done this? If so do you still apply when wet then add cap under heat?

My hairdresser has used this on me under the hair dryers, heat. Yes you would still use a cap. I put mine on wet, with the cap and a shower cap towel. This way it gets heat from my head. I do this for 30 min. Hope this help!