Shrinkage happens as a consequence of heat, like others said.
Other factors like the type of cycle in your washer or the soap brand don’t really affect the shrinking per se, but they absolutely have an effect on the life of your fabrics and yes, they can be responsible for deformation and irregularities in your garments (especially if the clothes are cheap, or if the products you use are not of great quality).
Bear in mind that some fabrics like cotton will shrink a bit no matter what, as the fibers get stressed a lot when you wet and then dry them.
Shrinkage happens as a consequence of heat, like others said.
Other factors like the type of cycle in your washer or the soap brand don’t really affect the shrinking per se, but they absolutely have an effect on the life of your fabrics and yes, they can be responsible for deformation and irregularities in your garments (especially if the clothes are cheap, or if the products you use are not of great quality).
Bear in mind that some fabrics like cotton will shrink a bit no matter what, as the fibers get stressed a lot when you wet and then dry them.
Cotton tangles as it gets wet. Tangled fibers get caught behind eachother in the fabric, which makes them slightly shorter.
But you can fix that by just gently pulling on them, either by ironing (but hahaha), or by literally just pulling…