K18 makes biotech hair care built around its leave-in molecular repair hair mask, with shampoos, conditioners, hair oil, heat protectant and dry shampoo alongside it, all vegan and cruelty-free.
The rule to know before you save: discount codes can't go on subscription orders, so you'll choose between a code and the Subscribe & Save price.
K18 describes its approach as biology-first hair care. It draws on biotech and biomimetics, borrowing solutions found in nature and recreating them in the lab, and it holds patents on its technology. The brand says the goal is healthier hair for every hair type in fewer steps and with fewer ingredients.
Newer additions include a hair longevity serum and a purple shampoo for blonde hair, next to a clarifying detox shampoo and color-safe options. Several products come in jumbo sizes, travel minis and sets. K18 also runs a professional site for stylists, a locator for certified salons and the TYB (Try Your Best) rewards program, which pays K18 coins for challenges, reviews and referrals.
When shoppers look for K18 coupons
K18 coupon searches stay fairly even all year: April leads, October trails.
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US Google searches, Oct 2025 to Sep 2026. Search interest, not sales.
Does K18 offer free shipping?
Yes. U.S. orders of $50 or more ship free, and that same $50 mark adds two free samples to the box.
How long does K18 shipping take?
Orders leave K18's warehouses in California and Ohio within 3 business days by USPS, DHL, UPS or FedEx; expedited service costs extra.
What is K18's return policy?
You get 90 days for a refund or replacement, but only on products bought from K18's own site; a salon purchase goes back to that salon.
What payment methods does K18 accept?
K18 lists HSA/FSA among its payment options, so a health account card can be tried at checkout for a mask or shampoo order.
More about shopping at K18
Refund timing
Start a return with customer service by phone or email, then allow up to two weeks for the money to show on your card.
Subscribe & Save
Listings show 10% off each delivery and the page headline says up to 15%; subscriptions ship only to the 50 US states and DC.
Email sign-up
Joining K18's marketing emails gets you 10% off your first order, with no code printed on the site itself.
Referrals
A friend gets $10 off a first purchase of $50 or more, and you get $10 off your next order in return.
TYB rewards
TYB (Try Your Best) pays K18 coins for challenges, reviews and referrals, worth up to $25, $41 or $57 off by tier on a $67 cart.
K18 runs on Shopify, so the discount box sits in the order summary on the checkout page.
Before you get there, decide how you're buying.
A one-time cart can take a code, such as the 10% welcome offer that follows the email sign-up, but a cart set to Subscribe & Save can't take any discount code at all.
If your cart sits just under $50, a small add-on is worth a look, since free shipping and the two samples both start there.
A code only matters for orders on K18's own site: a mask bought from a salon follows that salon's terms, refunds included.
Where the code box sits on Shopify's standard checkout (illustration; screens vary).
If your K18 code doesn't work
Combining offers: Discount codes can't be added to subscription orders.
New customers only: "10% off your order" is for a first order.
Subscribe & Save is the steadier discount if you go through a mask or shampoo regularly: 10% off each delivery on the listings, with skip or cancel anytime.
Cancel at least 24 hours before a shipment, or the change only takes effect from the next billing cycle.
TYB coins build up from reviews and challenges, and they cover part of a cart once it reaches $67.
The referral reward adds $10 off your next order when a friend's first purchase reaches $50.
K18 questions, answered
Can you use a K18 discount code on a subscription?
Discount codes can't be added to K18 subscription orders. The Subscribe & Save price, 10% per delivery on the listings, is the saving on those orders instead.
How do K18 coins work?
TYB (Try Your Best) members earn K18 coins for challenges, reviews and referrals. Coins turn into a discount of up to $25, $41 or $57 depending on your tier, once the cart reaches $67.
Can you pay for K18 with an HSA or FSA card?
HSA/FSA appears among K18's payment options, so your health account card can be used at checkout.
Where does K18 Subscribe & Save deliver?
Subscriptions ship only to the 50 US states and DC. Cancelling less than 24 hours before a shipment takes effect from the next billing cycle.
