C3 Addon SDK documentation

Welcome to the Construct 3 JavaScript SDK documentation. The JavaScript SDK allows third-party developers to create new addons for Construct 3. This includes:

  • Plugins: new kinds of object that appear in the Create new object dialog, with their own actions, conditions and expressions. Plugins are ideal for integrating third-party services, and are written in JavaScript. There are also two ways plugins can provide enhanced platform integration, accessing features not normally available in browsers:
    • Plugins can specify a Cordova plugin dependency for enhanced integration on mobile. See Specifying dependencies for more details.
    • Plugins can bundle a wrapper extension for enhanced integration on desktop. See the guide on wrapper extensions for more details.
  • Behaviors: new kinds of behaviors that appear in the Add behavior dialog, with their own behavior actions, conditions and expressions that get added to the object the behavior is added to. This can be used for creating new rapid prototyping features, or advanced gameplay logic that integrates with event sheets, and are written in JavaScript.
  • Effects: new kinds of visual effects that appear in the Add effect dialog. These are custom fragment shaders written in GLSL for WebGL and WGSL for WebGPU.
  • Themes: allow custom appearances for the Construct 3 editor, using additional CSS stylesheets to change the default editor appearance.


The Addon SDK files are hosted on the Construct Addon SDK GitHub repository. Follow the link, click the green Code button, and select Download ZIP to download a copy of the files.

There are sample files for example custom plugins, behaviors, effects and themes. The files for an addon can be zipped and renamed .c3addon to directly test it in the Construct 3 editor, via the Addon Manager.

While developing addons, be sure to use Developer Mode with a local HTTP server. It makes it much quicker to test since you don't need to keep creating .c3addon files, and much easier to fix problems, which otherwise can prevent Construct 3 from starting up.

Custom importer API sample data

The plugin SDK includes a sample plugin using the Custom Importer API. The included file customImporterSampleData.zip can be drag-and-dropped in to Construct 3 to demonstrate reading a custom format.

Addon SDK v2 migration

Construct is currently in the process of migrating from the legacy SDK, referred to as the Addon SDK v1, to the modern replacement with industry-standard encapsulation, referred to as the Addon SDK v2. The goal of this transition is to avoid on-going compatibility disasters that can end up ruining customer's projects, largely due to the lack of encapsulation in the Addon SDK v1. Support for the Addon SDK v1 for plugins and behaviors will ultimately be removed. We suggest addon developers consider updating any plugins and behaviors built with SDK v1 to SDK v2. Any new addons should only be developed with SDK v2. You can find out more about the migration in this forum thread. See Porting to Addon SDK v2 for more information about updating SDK v1 addons to SDK v2.

Learning web technologies

The Addon SDK documentation assumes you have a basic knowledge of JavaScript. A basic knowledge of HTML and CSS may also be useful. This documentation does not attempt to teach you these technologies. If you're just starting out, we recommend the MDN web docs as a good place to start. It provides thorough documentation on all aspects of the web platform, and also includes guides for learning web development.

Addon SDK Manual 2024-05-20