6 minute read
Olaplex is the most successful haircare launch of the last decade, and the numbering system is a large part of why. It is also, for a lot of people, completely opaque. The numbers do not run in order of strength, or order of use, or order of importance — they are essentially just the order in which the products were released.
So here is what each one actually does, and which numbers your hair genuinely needs.
How does Olaplex actually work?
Hair is held together partly by disulphide bonds. Bleach, permanent colour, heat styling and mechanical stress break those bonds, and once enough of them go, hair turns gummy when wet and snaps when dry.
Olaplex's patented ingredient finds broken bonds and relinks them. That is a genuinely different mechanism from a conditioner, which coats the hair, or a protein treatment, which patches gaps. It is why Olaplex works on damage that conditioning alone will not touch — and equally why it does very little for hair that is not actually damaged.
Choose your products by the condition of your hair and your routine. Olaplex also makes products for uncoloured hair, fine hair and curls; you do not need every numbered step.
What is Olaplex No.0 and do I need it?
Olaplex No.0 Intensive Bond Building Treatment 155ml is a pre-treatment primer, used on dry hair before No.3.
It exists for severely compromised hair — heavily bleached, over-processed, or on the edge of breakage. For everyone else it is an optional extra. If your hair is moderately damaged, skip it and go straight to No.3.
What is Olaplex No.3 and how should I use it?
No.3 is the product most people mean when they say "Olaplex". It is a weekly at-home bond treatment, and the current version is Olaplex No.3 Plus Complete Repair Treatment 100ml.
Two mistakes are near-universal here.
First, it is a pre-shampoo treatment, not a conditioner. For the current No.3 PLUS formula, dampen your hair, squeeze out excess water, apply through the lengths and leave for three minutes. Rinse, then shampoo and condition. If you have the original No.3 Hair Perfector, follow the instructions on that bottle; the formulas have different application times.
Second, match the frequency to the product and your hair. Olaplex recommends No.3 PLUS one to three times per week according to the level of damage. Start with a routine you can maintain and follow the directions on your bottle.
Which Olaplex shampoo should I use — No.4, 4P, 4C, 4D or Fine?
This is where the range has expanded most, and where the numbering gets genuinely useful.
- No.4 Bond Maintenance Shampoo — the standard. If in doubt, this one.
- No.4P Blonde Enhancer Toning Shampoo — purple shampoo for blonde and grey hair, cancelling brassy yellow tones
- No.4C Bond Maintenance Clarifying Shampoo — deep cleansing for product buildup, hard water and dry shampoo residue
- No.4 Fine Bond Maintenance Shampoo — the same repair without the weight, for fine hair that goes limp
- No.4 Curl Bond Shaper Hydrating Curl Shampoo — for curls and coils
- No.4D Clean Volume Detox Dry Shampoo — a dry shampoo, for between washes
No.4C is a clarifying step for build-up, used weekly or as needed rather than at every wash. Olaplex suggests every one to two weeks as a cautious starting point for colour-treated hair, and waiting at least two weeks after a colour service. Follow your stylist’s advice for freshly coloured or fragile hair.
If sulphates are a concern for you, our piece on whether sulphates damage your hair is worth reading before you assume the answer.
Which Olaplex conditioner do I need — No.5 or the leave-in?
Olaplex No.5 Bond Maintenance Conditioner is the rinse-out partner to No.4, and the two are designed to work as a pair.
Olaplex No.5 Leave-In Conditioner is the leave-in version, useful for hair that needs continued conditioning through the day.
For a weekly deep treatment, choose between Olaplex Intensive Bond Building Hair Mask (Rich Hydration) for dry, thick or coarse hair, and Olaplex Nourishing Bond Mask (Weightless) for fine hair that a rich mask would flatten.
What do No.6, No.7, No.9 and No.10 do?
These are the leave-in and styling numbers, and this is where people most often buy the wrong thing.
- No.6 Bond Smoother — a leave-in cream for frizz and flyaways. Best on medium to thick hair.
- No.7 Bonding Oil — a lightweight oil giving shine and heat protection to 232°C. Follow the amount recommended on your bottle, adjusting for hair length and thickness.
- No.7 Bonding Shine Serum Oil Mist — the same idea in a mist, easier to distribute on fine hair
- No.9 Bond Protector Nourishing Hair Serum — applied to damp hair before styling, protects against heat and pollution
- No.10 Bond Shaper Curl Defining Gel — curl definition with hold
For volume, Olaplex Volumizing Blow Dry Mist sits alongside these as a styling prep.
If frizz is your main reason for looking at No.6 or No.7, our guide on why hair gets frizzy and how to control it will help you work out whether the cause is damage, dryness or humidity — because the fix differs.
The honest minimum: which numbers do most people need?
If you colour your hair and want the biggest return for the least outlay:
No.3, plus No.4 and No.5. That is the core. The weekly treatment plus a shampoo and conditioner that maintain the work between treatments.
Add No.7 if you heat style regularly. Use No.4P when blonde or grey hair needs toning, alongside your regular wash routine. Add No.0 only if your hair is at breaking point.
Everything else is refinement. Buy the core three first, use them properly for two months, and then decide what your hair is still missing.
If you are unsure how damaged your hair genuinely is, or whether bond building is even the right approach, our team is happy to talk it through.
Prefer a guided shortlist? Use our free Olaplex routine finder to match the range to your hair and budget.