Book

• Introduction
• Basic usage
• Libraries
• Command-line interface / Commands
• The composer.json Schema
• Repositories
• Config
• Community

Articles

• Aliases Alias branch names to versions
• Autoloader Optimization How to reduce the performance impact of the autoloader
• Setting up and using custom installers Modify the way certain types of packages are installed
• Handling private packages Hosting and installing private Composer packages
• HTTP basic authentication Access privately hosted packages
• Setting up and using plugins Modify and extend Composer's functionality
• Scripts Script are callbacks that are called before/after installing packages
• Troubleshooting Solving problems
• Vendor binaries and the `vendor/bin` directory Expose command-line scripts from packages
• Versions and constraints Versions explained.

FAQs

• How do I install a package to a custom path for my framework?
• How do I install Composer programmatically?
• How do I install untrusted packages safely? Is it safe to run Composer as superuser or root?
• Should I commit the dependencies in my vendor directory?
• Which version numbering system does Composer itself use?
• Why are unbound version constraints a bad idea?
• Why are version constraints combining comparisons and wildcards a bad idea?
• Why can't Composer load repositories recursively?

API Docs

If you need to work with composer as a library you may also want to check out the API Docs