Guide to CLAUDE.md: What to Write in Claude Code's Instruction File

On October 4, 2026, DEV Community published a guide for Claude Code users on what a CLAUDE.md file is and what should go in it. According to the guide, CLAUDE.md is a Markdown file of instructions that Claude Code reads at the start of every session, and Claude treats it as context for the project.

The guide's advice on writing one is straightforward: the file is where build commands belong, along with conventions and rules that cannot be worked out from the code itself. Its contents should stay short and specific, and the file should be checked into git. The guide also notes that each Claude Code session starts with a fresh context window, and that two things carry knowledge from one session to the next; CLAUDE.md is one of them, working alongside automatic memory to preserve that context.

The material does not describe the file's structure, offer a template or example, or set any length limit. It cites no official documentation from Anthropic and mentions no changes tied to a particular version. As it stands, the account ends with the publication of that single guide on DEV Community, which frames CLAUDE.md as a session-level instruction file for carrying project knowledge, with brevity, specificity, and version control as the recommended practice.