---
"@context": https://schema.org
"@type": TechArticle
"@id": https://www.twilio.com/docs/flex/developer/ui/v1#article
headline: Flex UI 1.x.x
description: Use the Twilio Flex UI component library to build custom user experiences and custom behaviors for the Flex Agent Desktop and Flex Supervisor Desktop.
url: https://www.twilio.com/docs/flex/developer/ui/v1
inLanguage: en
dateModified: 2026-07-17T11:42:32.000Z
author:
  "@type": Organization
  name: Twilio Developer Education Team
publisher:
  "@type": Organization
  name: Twilio
---

# Flex UI 1.x.x

> \[!NOTE]
>
> For the Flex UI 2.x.x version of this content, see [The Flex UI](/docs/flex/developer/ui).

The Flex UI allows developers to build a custom user experience and custom behaviors for the Flex Agent Desktop and Flex Supervisor Desktop.

> \[!NOTE]
>
> [Auto-Generated Documentation for the Flex UI](https://assets.flex.twilio.com/docs/releases/flex-ui/1.33.0/) is accurate and comprehensive, and so may differ from what you see in the official Flex UI documentation.

The Flex UI Component Library is built in [React](https://reactjs.org/) and published on [NPM](https://www.npmjs.com/). [@twilio/flex-ui](https://www.npmjs.com/package/@twilio/flex-ui) is a node package that provides all the individual elements of the UI at the component level. It also provides a high-level API to interact with bundled SDKs such as the Voice JavaScript SDK, Programmable Chat, and TaskRouter.

## What you can do with the Flex UI

With the Flex UI, you can:

* Configure the UI or customize default properties for standard Flex components
* Customize themes and styles
* Control localization and templates
* Add, replace, or remove components
* Listen for, receive, and customize UI events with UI actions
* Customize agent desktop notifications using the Notifications Framework
* Modify the behavior and appearance of native channels and define custom channels with the Task Channel Definition API
* Add task or theme context to your custom components
* Access and control underlying SDKs through the Flex Manager object
* Programmatically customize the UI using Plugin Builder

## Building with plugins

If you're building with the Flex UI, chances are you're also using Flex Plugins. The Flex UI documentation will provide you with the programming interfaces and best practices you need to augment the Flex UI. The Plugin docs will explain the development environment, and help set you up to take advantage of the Flex UI's programmability.

## Next steps

* Build your first React-based Flex plugin
* Explore how the Flex UI uses Redux, a state management tool
* Discover the various components of the Flex UI