K18 and Olaplex are two of the hottest cult hair repair brands on the market. Both with high profile fan clubs that include Beyonce, Jennifer Aniston and Hailey Bieber alongside salon pros and pretty much everyone who’s run one through their hair.

Olaplex has been the gold star of the hair repair game since 2014 but newcomer, K18, popped up in 2021 and really got things buzzing on TikTok and beyond. Has it swooped in to knock Olaplex from its shiny podium?

If you're looking at purchasing K18 Molecular Repair Mask or Olaplex No.3 Hair Perfector you’re probably in the market for an intense hair repair system - something that brings bleached hair back from the brink, reverses damage caused by excessive heat-styling or something strong to repair breakage and seal split ends. And like most people, you've found yourself here, tossing up between Olaplex - the ultimate fan fave, or the new kid on the block, K18 - proving itself an extremely quick fix.

Which one are you going to reach for? What’s the difference? While no studies have been done to scientifically compare the two, we can compare them from hands-on experience plus a technical POV.

K18’s patented peptide mimics the natural structure of keratin building blocks and rebuilds and reconnects the polypeptide chains that make up the inner structure of the hair. It helps to repair the molecular chains of the hair thereby resulting in longer-lasting bond strength – This leave-in treatment turns back the clock in just 4 minutes.

Olaplex restores damaged hair by repairing from the inside out with a patented single ingredient, Bis-Aminopropyl Diglycol Dimaleate, which rebuilds broken bonds in hair – it almost patches over the damage like glue, but on a molecular level. Olaplex becomes part of your weekly wash regimen to improve hair strength, protect from within, and provide immediate results.

Olaplex No.3 Hair Perfector slots into your haircare routine two/three times a week as a pre-shampoo treatment. In 10 minutes it works to repair bonds at a structural level.

K18 Molecular Repair Mask is a leave-in treatment that’s applied to towel-dried hair post shampoo (no conditioner needed), in 4 minutes it works on the inner core of the hair to repair the keratin chains in the hair follicle to reverse the damage and restore elasticity.

They can both be used on any hair type. One thing to note is that K18 does contain ethanol so for curly and coily hair types, it is recommended to use an additional leave-in conditioner to make sure the hair is moisturized.

To treat your top hair concerns, colleen recommends:

Weak hair – Olaplex No.3 Hair Perfector
Brittle Hair – K18 Molecular Repair Mask
Damaged hair- Both
Split ends – Both
Bleached hair – Both
Curl pattern – Olaplex No.3 Hair Perfector
Long/Aging hair – K18 Molecular Repair Mask