Contentful

vs

ImpressCMS

A hybrid content management system that includes classic CMS and Headless CMS features. With dotCMS content managers can create content that fuels the brand experience. The API-first approach provided by the headless part of dotCMS allows developers to build extremely fast front-ends with popular third-party front-end framework and deliver content optimally. The content management system allows content creators to build engaging and memorable content that can be reused across sites.

Squidex is 100% open source headless CMS, built by passionated developers. With Squidex both individuals and organizations can handle content for the new web with ease. Squidex modular platform allows users to create content APIs that can be consumed by any frontend framework or technology in a matter of minutes. The framework itself can also be extended and tweaked to suite individual use-cases. Squidex is provided as a fully open source software released and free of charge, for the self-hosted community edition. For organizations that want to get up and running fast, commercially hosted solutions are provided.

Prismic is a commercial headless CMS and content (Content-as-a-Service) platform. With Prismic you can get your backend infrastructure and API up in the matter of minutes, so that you can focus on building the frontend that will be shown to your readers. The feature rich backend content management system provided by Prismic is free to use for one admin, and commercially provided to organizations with large content management teams.

PyroCMS is a free and open-source Content Management System written in PHP on top the web development framework Laravel.

WordPress powers roughly 30% of all web pages online. It's a free and open source CMS designed and developed for self-hosted publishing by Automattic, Inc. The software is written in PHP and utilize either MySQL or MariaDB as a database, and is compatible with most web hosts. Wordpress includes a plugin architecture and a templating system that can be used to extend and customize your website. These are commonly known as WordPress plugins and WordPress themes and make up a whole open source and commercial eco-system where anyone is free to create products for the platform. 

Drupal is a free and open-source CMS written in PHP. Drupal is used for creating website for businesses, political parties and governments. The CMS currently powers 2% of all websites on the internet.