CLAUDE.md: What it is and how to use it
Explore CLAUDE.md, a markdown instruction file that helps Claude Code understand project rules, build commands, and context in every session.
Stock photo for illustration only, not from the actual event
- CLAUDE.md is a markdown instruction file providing persistent context for Claude Code sessions.
- You can initialize the file automatically by running the /init command in your codebase.
- Files support nesting imports up to four levels deep using the @path/to/file syntax.
- Conflicting rules across concatenated files require manual resolution by developers.
Every session of Claude Code begins with a fresh context window, relying on specific mechanisms to carry knowledge forward. Developers write instructions into CLAUDE.md files, while auto memory captures notes that Claude generates independently from your corrections. Both sources load automatically at the very start of every new session.
Anthropic documentation defines CLAUDE.md as a dedicated space to record information you would otherwise need to explain repeatedly. Claude reads these guidelines and attempts to follow them, serving as helpful context rather than strict enforced configuration. For mandatory actions like pre-commit checks, documentation points users toward shell hooks, while permissions and environment variables belong in settings files like .claude/settings.json.
To create a new file, running /init allows Claude to scan your codebase and generate a tailored CLAUDE.md containing detected build commands, test instructions, and conventions. If a file is already present, the initialization command proposes improvements instead of overwriting your existing work.
Stock photo for illustration only, not from the actual event
A CLAUDE.md file can reside in multiple locations, influencing its reach across your directory structure. Claude Code loads files from your working directory and every parent directory above it, concatenating the contents rather than allowing one file to override another. The reading order spans from the broadest scope to the most specific project level.
Because the system concatenates files instead of overriding them, resolving contradictory rules remains the developer's responsibility. If instructions conflict, Claude may select one arbitrarily. Furthermore, if a repository utilizes an AGENTS.md file for alternative coding assistants, Claude Code reads it only when no CLAUDE.md or CLAUDE.local.md file exists in the active directories.
Managing instructions through concatenated markdown files requires careful structural planning, especially in monorepos. Understanding that files append rather than override helps teams implement global standards at the root level while tailoring specific overrides closer to working directories, provided they monitor rule consistency carefully.
You can also pull external content into your instructions using the @path/to/file syntax. Relative paths resolve directly from the containing file, supporting nested imports up to four hops deep. While import statements significantly improve organization, they do not reduce context window usage because imported files load immediately during launch.
Source: Dev.to
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