What version constraint format should I use?

Composer uses semver-style constraints. Common patterns: ^1.2 (compatible with 1.2.x), ~1.2.3 (patch-level compatibility), >=2.0 <3.0, or a specific version like 3.0.1. The caret (^) constraint is recommended for most packages.

What is PSR-4 autoloading?

PSR-4 maps a PHP namespace prefix to a filesystem directory. For example mapping "App\" to "src/" means Composer will look for class App\User in src/User.php. It is the modern standard for PHP autoloading.

What should the package name look like?

Composer package names follow the vendor/package convention using lowercase letters, digits, and hyphens, e.g. my-company/my-library. Both parts are required and must be lowercase.

What is the minimum-stability field?

It controls which development states of packages are allowed: stable (default), RC, beta, alpha, or dev. Leave it as stable unless you intentionally need pre-release packages.

Can I add dev-only dependencies?

Yes. Toggle the "Dev dependency" checkbox when adding a package to place it under require-dev instead of require. These packages are only installed in development environments.

Composer JSON Generator

Fill in your package details, add dependencies, configure autoloading and scripts, then download a ready-to-use composer.json file.

Package Info

Package Name *

Description

Type

License

PHP Constraint

Minimum Stability

Dependencies

dev

Leave empty to generate without dependencies.

PSR-4 Autoload

Namespace Prefix

Source Directory

Dev Namespace (optional)

Dev Directory

Scripts

composer.json

{
  "name": "vendor/package-name",
  "description": "",
  "type": "project",
  "license": "MIT",
  "require": {
    "php": ">=8.1"
  }
}

Quick-start

After downloading, run composer install in the same directory to fetch dependencies and set up autoloading.

Copied!

Summary

The Composer JSON Generator lets you build a valid composer.json file for any PHP project without writing JSON by hand. Configure your vendor/package name, license, PHP version constraint, required packages, PSR-4 autoload namespaces, and custom Composer scripts, then copy or download the result instantly.

How it works

Enter your package name in vendor/package format (e.g. acme/my-app).
Set a description, license, and minimum PHP version.
Add dependencies by typing the package name and version constraint.
Configure a PSR-4 autoload namespace and source directory.
Add optional Composer scripts such as test or lint commands.
Click Generate — preview the JSON and copy or download the file.

Use cases

Bootstrap a new PHP library or application quickly.
Generate a correct composer.json template when starting a project from scratch.
Learn the proper structure of composer.json without reading full documentation.
Add or validate version constraints before editing a real project file.
Set up PSR-4 autoloading for a custom namespace in seconds.
Create reproducible project scaffolding for team onboarding.

Frequently Asked Questions

Last updated: 2026-05-23 · Reviewed by Nham Vu