Five checks tell you whether a bag is truly waterproof before you trust it with a phone or a laptop.
1. Look for a rating. A waterproof bag should state an IPX rating. IPX5 or IPX6 means rain and water jets; IPX7 or IPX8 means immersion. "Waterproof" with no rating is a claim, not a specification.
2. Check the fabric. PVC tarpaulin and TPU-laminated fabrics have a continuous waterproof layer. Plain nylon or canvas, even with a water-repellent finish, does not.
3. Look at the seams. Turn the bag inside out. Welded seams look like flat, fused bands with no thread. Stitched seams in the waterproof shell need to be fully taped; if you can see needle holes, water can get through.
4. Check the closure. A roll-top must be rolled at least three times before buckling. A waterproof or airtight zip must be closed fully to its end stop. An ordinary zip, even with a storm flap, is not waterproof.
5. Test it. Put a dry paper towel inside, close the bag as you would use it, and hold it under water in a bath or sink for several minutes, pressing gently. If the paper comes out dry, the bag and your closing technique work.
At our factories, waterproof bags are tested before shipment: IPX5 and IPX6 models pass a heavy rain and water-jet test, and IPX7 and IPX8 models a full water-immersion test of 2+ hours. See how dry bags are tested before shipment.