Short version: A case study explains a particular project through its brief, decisions, solution and documented outcome. It helps readers understand why the work took the shape it did.
What to include: Introduce the client and starting situation, describe the problem and constraints, explain the chosen approach and show the deliverables. Then state what changed and which evidence supports that account.
For a website, useful evidence might include the old and new structure, a walkthrough of the buying journey or metrics from comparable periods. For an identity, show how the design rules carry from the logo into packaging, the website and other materials.
How to present results: Separate a completed deliverable from a business outcome. Launching a website does not by itself demonstrate higher sales. Give the period and context for any metrics. Where data is unavailable, describe a verifiable change without inventing numbers.
Before publication, check the facts and permission to use client names, quotes, screenshots and internal information. A useful case study lets a prospective client judge whether the challenge and approach are relevant to their own project.
Related terms: social proof, value proposition, and customer journey.