Best Backpack Liner

A pack liner is the most reliable single piece of waterproofing gear a hiker can carry, since it keeps the main compartment's contents dry regardless of whether the pack's shell, seams, or zippers leak. Choosing one comes down to durability needs, pack size, and how the gear inside needs to be organized.

What is a pack liner and why use one?

A pack liner is a waterproof bag placed inside a hiking backpack's main compartment before packing, so that gear stays dry even if the pack's outer fabric, seams, or zippers let water through during sustained rain. It works because it doesn't depend on covering every seam and zipper on the outside of the pack — the barrier is on the inside, sealed independently of the shell.

This matters because no hiking backpack's shell is fully waterproof: stitched seams and zipper coils let water through under sustained rain even on packs with a fresh DWR coating. A liner sidesteps that problem entirely rather than trying to solve it at the shell.

What types of pack liners are there?

There are three common types of pack liners: disposable trash compactor bags, purpose-built roll-top pack liners, and individual dry bags used to compartmentalize gear inside the pack. Each suits a different balance of cost, durability, and organization.

• Trash compactor bags: cheap, lightweight, and thicker than standard kitchen bags; twist and fold shut; typically replaced every few trips as they tear
• Purpose-built roll-top liners: heavier-duty fabric sized to specific pack volumes, with a roll-top closure for a more reliable seal; reusable over many seasons
• Individual dry bags: separate waterproof sacks for specific gear categories — a sleep system, spare clothing, electronics — that also keep items organized, not just dry

What size liner do I need?

Match liner size to the pack's rated volume rather than sizing down, since a liner that's too small won't reach the top of a fully loaded pack to seal properly, and a liner slightly larger than the pack's volume rolls down further for a more secure closure. A liner close to the pack's own liter rating is usually the right starting point.

Hikers using individual dry bags instead of a single full-pack liner should size those bags to the gear categories they're packing — a compressible sleep-system bag, a mid-size bag for spare clothing, and a small bag for electronics — rather than one oversized bag that leaves air gaps and makes gear harder to find.

Roll-top liner vs dry bags: which is better?

A single roll-top liner is simpler and lighter for most three-season hiking trips, since it protects everything in the main compartment with one seal and one closure step. Individual dry bags add weight and cost but make gear easier to find without unpacking the whole bag, which matters more on multi-day trips where the pack gets opened and repacked repeatedly.

Trade-offs run in both directions. A single liner is faster to pack and unpack and adds less weight, but finding one item means partially emptying the whole liner. Multiple dry bags add a small amount of weight and cost from extra material and closures, but let a hiker pull out just the rain layer or the stove without disturbing the sleep system. Many experienced hikers combine both: a liner for the bulk of the gear, plus one or two small dry bags for electronics or anything that needs to stay both dry and separate.