Developer tool

Composer Platform Checker

Paste composer.json to list PHP constraints and ext-* platform requirements without running Composer.

How it works

How to use

Paste a composer.json document. The checker validates JSON and reports the PHP constraint, declared ext-* extensions, and package requirements.

Safety limits

This tool never runs composer install, update, or downloads packages. It performs static JSON analysis only.

Related Composer tools

Also see the Composer.json Validator, Constraint Explainer, and PSR-4 Checker. None of these tools run Composer install/update.

Run in browser

AJAX processing only. No remote PHP execution sandbox. Results are not indexed.

Static JSON analysis only — Composer install/update is never executed.

Safety notes

  • Submitted tool contents are not written to analytics or search logs.
  • This site never evaluates arbitrary PHP from the browser.
  • Generated configs are starting points—validate on a staging host before production.