You have two choices for building the user interface for your Forge app – the UI kit, and custom UI. The UI kit allows you to create a straightforward UI using a set of Atlassian-supplied components, put together using relatively simple code. Custom UI gives you more room to use Atlassian-supplied and third-party hooks, components and such, while also allowing you to employ more complex HTML, CSS, static resources (such as images) and source code, all of which can be hosted in Atlassian’s cloud with custom UI but not the UI kit. Both types of UI involve writing code in a React-like pattern, which makes sense in that various components available from Atlassian are based on React.

Forge is Atlassian’s next-generation framework for building apps that integrate with Confluence, Jira, or Jira Service Management. Forge provides Web UI elements, APIs and deployment environments that enable developers to create fully-featured apps within Atlassian’s cloud infrastructure through the use of JavaScript, HTML, CSS and other Web technologies. Forge apps can be distributed via the Atlassian Marketplace as software to which any Atlassian Cloud customer can subscribe.