Your zipper probably just needs a squeeze

If your backpack zipper keeps splitting apart behind the slider, the fix is usually to tighten the slider with pliers.

The zipper slider gets loose from years of tugging, and once it’s loose it stops pressing the teeth together. That’s why the two sides keep separating behind it. Grab a pair of pliers, find the slider, and squeeze it gently on the sides—the wide parts, not the top. Don’t go crazy; you want it snug, not crushed. Try the zipper, and squeeze a little more if needed.

Occasionally the problem is something stuck in the teeth or a bent tooth. Check for fabric jammed in the zipper and run a finger down the teeth to feel for any bent ones. But nine times out of ten, the loose-slider trick fixes it.

Two minutes with pliers beats buying a new backpack.