Learn Claude Code

Custom slash commands and settings.json

Create your own Claude Code slash commands with markdown files, and configure settings.json for permissions, environment and team-wide defaults.

Lesson 3.3⏱ 8 min read🚗 Daily driver❓ 3-question quiz
The short answer

Save reusable prompts as markdown files in .claude/commands/ (shared with your team) or ~/.claude/commands/ (personal) to create your own slash commands. Use settings.json files to pre-approve safe commands, block risky ones and share configuration.

Turn repeat prompts into commands

If you type the same instructions over and over, make it a command. Create a markdown file:

.claude/commands/review-diff.md
Review the current git diff for:
- bugs and edge cases
- security issues
- unclear naming
Give a prioritised list. Be concise.

Now type /review-diff in any session in that project. 🎉 (Avoid plain /review: it is a built-in shortcut for /code-review, so your file would never run.)

  • .claude/commands/: project commands, committed to git, shared with the team.
  • ~/.claude/commands/: personal commands, available in all your projects.

Passing arguments

Use $ARGUMENTS as a placeholder for whatever you type after the command:

# .claude/commands/blog.md
Write an 800-word SEO blog post about: $ARGUMENTS
Use British English, H2 subheadings and a short FAQ.
/blog how Irish businesses can automate invoicing with AI
Tip: commands can include frontmatter (a small block of settings at the top of the file) such as a description shown in autocomplete. Newer Claude Code versions fold commands into skills, which add more power (see Level 4).

settings.json: where configuration lives

  • ~/.claude/settings.json: your personal settings everywhere.
  • .claude/settings.json: project settings, committed and shared.
  • .claude/settings.local.json: your personal overrides for this project (not committed).

A simple permissions example:

{
  "permissions": {
    "allow": ["Bash(npm run test:*)", "Bash(npm run lint)"],
    "deny": ["Read(./.env)", "Bash(rm -rf:*)"]
  }
}

This pre-approves running tests and lint, and blocks reading your secrets file.

Team configuration done right

  • Commit shared commands, settings and CLAUDE.md so every teammate gets the same experience.
  • Keep secrets out of committed files; use environment variables instead.
  • Prefer deny rules for anything destructive or sensitive.
Analogy: CLAUDE.md is the staff handbook, custom commands are the standard operating procedures, settings.json is the building's access-card system.

Check yourself

Three quick questions to check it stuck.

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Frequently asked

How do I create a custom slash command in Claude Code?

Create a markdown file in .claude/commands/ (project) or ~/.claude/commands/ (personal). The file name becomes the command name, and the content is the prompt.

Where is the Claude Code settings.json file?

User settings live in ~/.claude/settings.json, shared project settings in .claude/settings.json and personal project overrides in .claude/settings.local.json.

How do I pass arguments to a custom Claude Code command?

Use the $ARGUMENTS placeholder in the command file. Whatever you type after the command name replaces it.