What card sorting actually is
You have a list of pages, features or offerings, and you are guessing at category names before committing to a navigation.
The question in front of you is not how to run a study.
It is whether a card-sorting study is the right method for your situation at all.
Here is the one reason this decision matters: card sorting and tree testing answer different questions.
Picking the wrong one means running research that cannot tell you what you actually need to know.
This article walks through that decision, the documented preparation guidance, and the honest limits of what a card sort can tell you.
Card sorting is a research method in which participants place individually labeled cards into groups according to criteria that make the most sense to them.
The cards can represent pages, links, images, or descriptions of pages users would navigate to on your website, according to nngroup.com.
The purpose is to uncover users' mental models of your information architecture.
In plain terms, you learn how the people you are building for expect your content to be organized, so they can find things more easily.
A simple example from the same source: an athletic-clothing ecommerce site gives a participant cards labeled Sweatshirts, Gloves, Hats and Tank tops.
The participant might put Sweatshirts and Tank tops into a group called Tops, and Gloves and Hats into a group called Accessories.
That grouping, and the label the participant chose, is the output you are after.
This is a user-experience decision, not just a builder preference.
User experience covers all aspects of a user's interaction with a company, its services and its products, per Don Norman and Jakob Nielsen in nngroup.com.
The first requirement is meeting the customer's exact needs without fuss.
Navigation that matches how users think is part of meeting that requirement.
Card sorting or tree testing: which question are you asking?
This is the core decision, and the two methods are not interchangeable.
Use card sorting when you need help organizing content, services or product offerings in a way that is easy and intuitive for your users.