How the preview works
Inpainting regenerates only the masked pixels, using everything unmasked as context. Your bone structure, ears, jawline, and the scene's light direction all constrain how the new hair is drawn — where it falls, how it catches highlights, where it casts shadow on the forehead and neck.
The face itself is never regenerated, so there's no uncanny drift in your features. If a result looks off, it's almost always a masking issue rather than an identity issue — see the masking notes below.
Prompt like you're briefing a stylist
Salon vocabulary works because the model has seen it captioned on millions of images. Name the cut: 'french bob with curtain bangs', 'textured crop, faded sides', 'long layers past the shoulders'. Then the color in real colorist terms: 'ash brown', 'copper balayage', 'platinum with dark roots' — each is far more precise than 'lighter'.
Add finish and texture last: 'glossy straight', 'matte tousled waves', 'defined curls'. Texture words change the render dramatically, and they're also the honest variable — your real hair's texture will influence how a cut behaves, so preview a couple of finishes rather than just one.
Masking hair without haunting your hairline
Hair is the softest-edged object in any portrait — wisps, flyaways, and translucent strands extend well past the apparent outline. Mask a little beyond the visible hair everywhere, especially around the hairline and temples, so the model can rebuild a natural edge instead of tracing a hard boundary.
Mask for the target length, not the current one. Going from short to long means masking the shoulder and chest space where the new hair will fall; going long to short means including all the current hair so none of it survives the swap as a floating remnant.
More than salon previews
Character and avatar work uses this constantly: keep a face consistent while cycling hairstyles across a character sheet, refresh a profile picture without a new photoshoot, or test which look reads best at thumbnail size for a creator brand.
It's also a quiet workhorse for professional photos — checking whether the shorter cut reads more 'senior consultant' before committing, or updating the hair in an older photo you otherwise love so it matches how you look now.