A CTF writeup is not only a victory note; it is a technical explanation of how a problem was understood, tested and solved. Start by describing the challenge category, the given files or service, the first observations and the suspected weakness. This gives the reader context before the exploit path begins.
The best writeups include reasoning, not only commands. Explain why a tool was selected, what each important result suggested and how that changed the next step. If a path was a dead end, summarise it briefly so the final method feels reproducible rather than accidental.
Evidence should be precise and ethical. Show the payload, decoded value, binary behaviour, web request, forensic artefact or cryptographic step that proves the solution. Avoid hiding the logic behind a screenshot. The academic value is in explaining how the evidence supports the conclusion.
End with a short lesson learned section. Identify the vulnerability class, the defensive control that would reduce the risk and the skill improved by the challenge. This turns a CTF solution into a study note that supports coursework, lab reflection and future revision.