WHAT TO LOOK FOR: Backpacks come in a wide range of styles and sizes.
Some are really like small soft sided suitcases with straps that can go over shoulders.
Others are for very serious sportspeople going off road and backpacking for weeks carrying tents, supplies, water and food.
Heavy duty, large capacity and heavy, usually with fantastic harnesses to help distribute the weight.
Others are completely water proof and for people swimming rivers, canyoning, or walking in very wet conditions.
However for a Camino the best backpacks to look for are light in weight, not too large and most importantly comfortable.
The weight is a function of size usually measured by “volume”
As an example a small backpack for a Camino would be around 30 L and a large one 45 L perhaps expandable to 50 L. As accomodation is available in many places along the more popular Caminos then tents and cooking gear is not needed, although some people will elect to camp. Others may take a donkey, or ride a horse. Cyclists will store everything in bags attached to their bikes.
Weight. Note the more zips, flaps, loops and pockets on the backpack then the heavier it will be. Some manufacturers offer good quality backpacks at around 1kg. They achieve this by minimising the zips etc as well as the material in the harness. This means less padding or sometimes no solid frame.
Most also can be adjusted for different back lengths, a critical function to make sure it fits your body length and shape.
REI and others have some great videos available on line to show how to fit and adjust backpacks, what the various straps are for and lots more.
Please check the pages in the navigation area for details on some popular brands and one with a revolutionary design.