How do you keep dark clothes from fading?
Dark clothes fade for three reasons: mechanical abrasion in the wash, detergent chemistry, and light exposure. The dye sits on and in the fiber, and every wash cycle works it loose a little. You cannot stop it entirely, but you can slow it down a lot with wash habits that cost nothing extra.
Wash cold, and wash less
Cold water is the single biggest lever. Hot water opens fiber structures and dissolves dye faster, while cold water keeps dye locked in and cleans just as well for normal soil. Turn dark garments inside out before washing. This moves the abrasion to the inside of the garment, where fading does not show, instead of the outside face everyone sees.
Wash darks only when they need it. Every cycle fades a little, so two fewer washes per month across a wardrobe adds up to meaningfully longer color life. Air out worn garments and spot-clean marks instead of defaulting to the machine.
Use less detergent than you think
Most people use far too much detergent. Excess detergent leaves residue that dulls darks and gives the wash cycle more chemistry to work against the dye. Use the smaller end of the recommended amount, and skip the optical brighteners: they are designed for whites and work by depositing fluorescent compounds that make darks look chalky.
A detergent formulated for darks is a real product, not marketing. They tend to be lower-foam and free of brighteners and harsh bleach alternatives. It is one of the few specialty detergents with a genuine job to do.
Short cycles and line drying
Shorter cycles mean less time tumbling, and tumbling is mechanical wear. A quick or delicate cycle on cold handles everyday darks fine. Skip the dryer when you can: heat and tumbling together are the fastest fading combination in the laundry room. Line dry inside out, out of direct sun, because UV bleaches dye just as surely as it bleaches everything else.
When fading is a dye-quality problem
Some fading is not your fault. Garments dyed with cheap reactive dyes or dyed too quickly lose color fast no matter what you do. If a black tee goes gray after five careful washes, the dye job was poor, not your habits. Higher-quality dark garments use dyes and dye processes that penetrate the fiber fully, and they hold color noticeably longer.
The routine that works
Cold water, inside out, darks-only loads, modest detergent without brighteners, short cycles, and line drying out of direct sun. Nothing exotic. Done consistently, these habits keep blacks black for years instead of months, and they cost less than the garments they protect.