What is hair porosity in simple terms?

It is how easily your hair takes in water and product, and how well it holds onto them. It depends on whether the cuticle scales on the outside of each strand are lying flat (low porosity) or raised and gapped (high porosity).

Can hair porosity change over time?

Yes. You are born with a baseline, but coloring, bleaching, heat styling, hard water, and sun can raise the cuticle and move your hair toward high porosity, especially at the ends.

Is low or high porosity better?

Neither is better or worse, they simply need different care. Low porosity hair resists moisture going in, high porosity hair resists moisture staying in. The goal is matching your routine to your level, not changing your level.

How do I find out my hair porosity?

Watch how your hair behaves with water and products, run a finger up a strand to feel the cuticle, and check how long it takes to air dry. A guided porosity quiz combines these signals into a clearer result than any single home test.

Hair Porosity Explained: The Complete Guide

Hair porosity is your hair's ability to absorb and retain moisture, and it is set by the shape of the cuticle, the outer layer of overlapping scales that protects each strand. When those scales lie flat and tight, water and products struggle to get in (low porosity). When they are raised or gapped, moisture rushes in and escapes just as fast (high porosity). Most people sit somewhere between the two (medium porosity). Knowing your level is what tells you which products, oils, and routines will work on your hair, and which ones will just sit on top or wash straight out.

What porosity actually measures

Every strand of hair has three layers: the inner medulla, the protein-rich cortex that holds most of its strength and moisture, and the cuticle on the outside. The cuticle is made of keratin scales that overlap like roof tiles. Porosity describes how open or closed those scales are, because that gap is the path water and product ingredients use to reach the cortex.

This matters more than hair type (straight, wavy, curly, coily) when you are choosing products. Two people with the same curl pattern can need completely different routines if one has low porosity and the other has high porosity.

The three porosity levels

Porosity falls on a spectrum with three practical points along it.

Low porosity: cuticles lie flat and tightly sealed. Water beads on the surface, hair takes a long time to get fully wet, and products tend to sit on top or build up rather than absorb.
Medium porosity: cuticles are slightly loose. Moisture goes in and stays in at a balanced rate. This hair is usually the easiest to style and holds treatments well.
High porosity: cuticles are raised, gapped, or damaged. Hair soaks up water almost instantly, but loses it just as quickly, so it often feels dry, rough, or frizzy and dries fast.

Is porosity genetic or caused by damage?

It can be both. Some people are born with naturally low or high porosity, and it often runs in families. Porosity can also shift over time. Chemical processing (color, bleach, relaxers), repeated heat styling, hard water, UV exposure, and rough handling all lift or crack the cuticle, which pushes hair toward high porosity.

That is why a person with genetically low porosity hair can still develop high porosity ends after years of coloring or heat, while the roots stay low. Reading your hair by section, not as one single number, gives a more honest picture.

Take the free hair porosity test

Why porosity changes your whole routine

Once you know your level, product choices stop being guesswork. Low porosity hair needs lightweight, easily absorbed products and a little warmth to open the cuticle, and it clarifies often to shed buildup. High porosity hair needs richer creams, sealing oils or butters, and often protein to temporarily fill the gaps in the cuticle so moisture stays put.

Use the levels below as a map. The dedicated guides go deeper on the signs, causes, and exact care approach for each.

Frequently Asked Questions

What is hair porosity in simple terms?: It is how easily your hair takes in water and product, and how well it holds onto them. It depends on whether the cuticle scales on the outside of each strand are lying flat (low porosity) or raised and gapped (high porosity).
Can hair porosity change over time?: Yes. You are born with a baseline, but coloring, bleaching, heat styling, hard water, and sun can raise the cuticle and move your hair toward high porosity, especially at the ends.
Is low or high porosity better?: Neither is better or worse, they simply need different care. Low porosity hair resists moisture going in, high porosity hair resists moisture staying in. The goal is matching your routine to your level, not changing your level.
How do I find out my hair porosity?: Watch how your hair behaves with water and products, run a finger up a strand to feel the cuticle, and check how long it takes to air dry. A guided porosity quiz combines these signals into a clearer result than any single home test.

Take the free hair porosity test

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By GetHairType editorial.

Last updated: July 2026