Storyblok

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PyroCMS

Strapi is a free and open source headless CMS developed with JavaScript for Node.js. The software makes it really simple to generate REST and GraphQL APIs. Simply create your database schema and relationships in the Strapi admin panel UI, and Strapi will auto-generate API endpoints to represent the data structures provided. Strapi comes packed with features you come to expect from normal CMS's such as authentication, authorization, content management and a media library. The software can be used for free and can be self-hosted on any server and platform. Extra enterpise functionallity is currently being developed, and will be sold at cost.

Ghost is a free and open-source headless CMS and blogging platform developed by Ghost Foundation. With Ghost you can manage content in style, the user experience provided by the software is intuitive and encourages writing. Ghost is written in JavaScript for the Node.js platform and is released under the MIT license.

An open-source tool for managing content across all your omni-channel digital experiences. Directus is free and open-source headless CMS written in PHP, that takes a data first approach. Developers and content creators use Directus to manage content and generate a powerful API that can be used by any frontend technology. Directus can be self-hosted and is absolutely free.

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.

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. 

Joomla is a free and open-source content management system written in PHP. The CMS is built entirely by volunteers from all over the world and has a strong community that provide educational resources, and extensions.