What a virtual hair try-on can and cannot show
A virtual hair try-on can show the idea of a change on your own face: a new length, a fringe, a warmer or cooler colour, a fuller brow. It cannot show how your hair will behave, what a colourist can achieve on your hair's condition, or how a product will wear. Treat it as a preview, not a promise.
Updated October 20, 2026
Illustration of a Tressaly look on a model created for this page. Hair, brows and makeup change; the face, the skin and the framing do not.
What can an AI preview show, and what can it not?
| A preview can show | A preview cannot show | |
|---|---|---|
| Hair shape | Length and silhouette of a cut or fringe against your face | How the hair moves, dries, shrinks or holds through a day |
| Hair colour | A colour's temperature and depth next to your skin, in the light of your photo | The exact shade a chemical process produces on your hair and its condition |
| Brows | Density and definition in the frame you already have | How a product applies to your hair direction |
| Makeup | Where colour sits and roughly how strong it reads | Texture on skin, wear time, how it looks in other light |
| Comparison | The same photo before and after, so you can judge one change at a time | A result from another angle, in other lighting or in motion |
Everything in the right hand column depends on your real hair, your real skin, the products and the hands applying them. That is not a limitation of one app; it is what a still image is.
What should a good preview never change?
- Bone structure: nose, jaw, chin, face width, eye size, lip volume. A preview that slims or enlarges is editing you, not your hair.
- Skin: tone, texture, pores, freckles, scars and moles. A smoother or lighter face after a hair change means a filter has been applied.
- White balance: a hair colour change that also warms or cools the skin and background is showing you a colour grade, not a colour.
- Framing: same crop, same scale, same position, so that pupils, nostrils and lip corners line up between before and after.
- Labelling: the image is an AI preview and should say so where you see it.
These are the same expectations international AI ethics guidance puts on any system that acts on a person's image: transparency about what was generated and human judgement kept in the loop. In a try-on they are also practical. If the face changed, you cannot judge the hair.
How do you judge whether a try-on is honest?
- Compare before and after with a sliderPupils, nostrils, lip corners and the hairline should stay in the same place. If a feature moves, the face was redrawn.
- Check the skin outside the changeZoom into a cheek or the forehead. Colour, texture and marks should be identical in both images.
- Check the backgroundA hair colour change should leave the wall behind you the same colour. If it shifted, the whole image was graded.
- Look for the AI labelA preview that does not say it is generated is asking you to take it as a photo.
- Ask what happens to your photoWhen it is deleted, who processes it and whether it trains anything. The answer should be short and specific.
- Treat strong changes as salon resultsA big lift, a strong tone change or a very different length depends on your hair's condition and a professional's judgement. The preview shows the idea; the salon decides what is possible.
Why does lighting matter so much?
Skin colour in a photograph is a function of the light as much as of the skin. The International Commission on Illumination published a standard in 2025 for measuring human skin colour because results change with illumination, body location and measurement method. A selfie in mixed indoor light misleads you and the model in the same direction, so a preview made from it shows a colour against a skin tone neither of you really has. Facing a window with no filter is the single most useful thing you can do before any try-on.
What does Tressaly show, and what does it leave alone?
Tressaly reads one selfie and returns a read of six areas: hair shape, hair colour, brows, eyes, cheeks and lips, each a specific change or leave as is, with the reason it suits the face in that photo. It then draws Everyday, Evening and Work looks on your own photo and shows each against the original with a slider.
It changes hair, brows and makeup only. It never alters bone structure, nose, jaw or eye size, never scores or rates a face and never applies a filter. Every look is labelled as an AI preview, and each one is checked on your iPhone with Apple's Vision framework so that a look whose face has drifted from your photo is regenerated once or dropped rather than shown. How Tressaly checks that your face did not change. Your selfie is deleted from Tressaly's servers within 24 hours and is never used to train models. Products listed behind a look are described by attribute, in your shade, and linked to their listings on AliExpress. The first read is free.
Questions
Are virtual hair try-ons accurate?
They are accurate about shape, length and the temperature and depth of a colour against your skin in the light of your photo. They are not accurate about how hair behaves, what a chemical process will produce or how a product wears. Judge them as a preview of an idea.
Can a try-on tell me my face shape?
Tressaly does not assign you a face-shape label from a photo. It reads measurable relationships, such as how your forehead, cheekbones and jaw relate and where your part and hairline sit, and cites those when it suggests a change.
Does Tressaly change my face?
No. It changes hair, brows and makeup only, keeps your skin and framing as they were, and labels every image as an AI preview. Each look is checked on your iPhone and is not shown if the face has drifted from your photo.
What happens to my photo?
It is sent to Google's Gemini models to write your read and draw your looks, only after you agree in the app. It is deleted from Tressaly's servers within 24 hours and is never used to train models, sold or used for advertising.
Sources
- UNESCO. Recommendation on the Ethics of Artificial Intelligence, 2021.
- UNESCO. Ethics of Artificial Intelligence, 2021.
- International Commission on Illumination. CIE 256:2025 Measurement of Human Skin Colour, 2025.
- U.S. Food and Drug Administration. Color Additives and Cosmetics: Fact Sheet.
Guides describe styling choices, not medical or dermatological advice. Tressaly reads one selfie and shows these choices on your own photo. How a read works.