Compact CampingPack rain cover or liner: which keeps gear dry?
These solve related but different problems. A cover keeps the pack itself from soaking through. A liner keeps what's inside dry even if the cover fails, or isn't there at all.
What a rain cover actually does
A rain cover, like the VAUDE Raincover for Backpacks (sold in sizes from 6–15 L up to 55–80 L to match different pack volumes), stretches over the outside of a pack and sheds rain before it soaks into the fabric. Most compact backpacks are only water-resistant, not waterproof, so in sustained rain the fabric itself will eventually wet through; a cover buys real time and keeps the pack lighter by not letting it absorb water at all.
Where a cover falls short
Wind-driven rain can get up underneath a cover at the back panel, where it has to leave a gap for the hip belt and shoulder straps. A cover also does nothing once you're fording a stream or the pack gets set down in standing water — it protects against rain from above, not immersion.
What a liner does instead
A pack liner — a large waterproof bag lining the inside of the main compartment, whether a dedicated dry-bag-style liner or even a heavy-duty bin liner — keeps everything inside genuinely dry regardless of what happens to the pack's exterior. It doesn't stop the pack fabric itself from getting wet and heavier, but the gear inside stays dry through rain, stream crossings, or a pack set down in the wet.
Why most experienced hikers use both
A cover and a liner solve different failure points, and together they cost very little extra weight — a liner can be nearly free if you use a sturdy bin liner instead of a dedicated product. The cover keeps the pack itself lighter and drier in normal rain; the liner is the actual guarantee that your sleeping bag and spare clothes stay dry no matter what the weather or terrain does.
If you can only carry one
Carry the liner. It protects the gear that actually matters — dry insulation and clothing are a real safety issue, a slightly heavier wet pack fabric is just an inconvenience. A cover is the upgrade once you've already got a liner sorted, not a replacement for one.
Verdict
For sustained rain or a pack that isn't already waterproof-coated, a cover sized to match your pack — the VAUDE range covers most compact pack sizes — earns its small weight. Pair it with a liner rather than relying on either alone; together they cover both the pack itself and what's inside it. See our dry bag picks for liner-style options sized to different gear loads.