The laundry room is usually the tightest room in the house, and the spot beside the washer or dryer is the tightest part of it. You've got a vertical seam between the machine and the wall that's too thin for a basket and too shallow for a shelf unit — so the detergent ends up on top of the machine in a falling tower of bottles. There's a cleaner way to use that seam.
The seam beside the washer is the same problem as the fridge
It's a narrow gap, just in a different room. A narrow gap shelf slides into it the same way it slides beside a fridge: about 5.9 inches of carbon steel that clips onto the seam and gives you a caddy for the things you reach for every load. Dryer sheets, stain spray, the lint brush, a spare roll of dryer balls — all off the machine top and into a spot made for them.
Why not just stack on top of the washer
The top of the washer looks like a shelf but it isn't one. Bottles tip when the machine vibrates, and anything round rolls off mid-spin. A slide-on shelf hugs the seam instead of balancing on a shaking lid, so the detergents stay put through the cycle. It also frees the lid for the one thing it's actually for: folding clean clothes straight out of the dryer.
Carbon steel because laundry is wet
Laundry rooms are humid, and plastic shelves film over and sag. Carbon steel wipes clean and doesn't stain, which matters when a cap leaks. The shelf installs with no drilling, so it won't mark the wall or the appliance — handy if this is a basement or rental unit you don't own.
Reclaim the seam by your machines with a slim gap shelf, or see the narrow storage range.