> Markdown version of [Collaboration Kit (deprecated)](https://vaadin.com/docs/next/tools/collaboration). Section index: [llms.txt](https://vaadin.com/docs/next/tools/llms.txt)
# Collaboration Kit (deprecated since V25.3) Flow
Collaboration Kit, formerly known as Collaboration Engine, is a solution for building real-time collaboration features into web applications with a few lines of code. This means that users can work collaboratively — edit and communicate in real time — directly within secure Vaadin web applications.
Collaboration Kit is superseded by [signals](https://vaadin.com/docs/next/flow/ui-state/shared-signals.md) and is scheduled for removal in Vaadin 26.
See [Migrating from Collaboration Kit to Signals](https://vaadin.com/docs/next/tools/collaboration/migrating-to-signals.md) for how.
Collaboration Kit is open source, licensed under the [Apache License 2.0](https://www.apache.org/licenses/LICENSE-2.0).
## Supported Use Cases
Collaboration Kit supports a few use cases, which are described in the following sub-sections.
### Collaborative Form Editing
Users can edit forms together in real time.
[Image: Personal information form being edited currently by another user]
### Avatars
Users can see who else is looking at the same data they’re viewing. The avatars are updated when users join or leave.
[Image: Avatar group with three avatars visible, and three more truncated together]
### Real-Time Discussion
Users can send messages to each other within the application, either in real time or asynchronously.
[Image: Chat between users on updating information]
### Low-Level API
Build your own collaborative experiences by sharing data in `CollaborationMap` and `CollaborationList` data structures.
See the Collaboration Kit Sampler for live examples, along with source code.
[Collaboration Kit Sampler](https://ce-sampler.demo.vaadin.com/)
## How the Kit Works
Collaboration Kit offers an intuitive library that connects to a collaborative backend, the *engine*.
This backend handles the sharing of data and user-state among application instances in real time. It currently runs in-memory on the application server, although a standalone version that you can deploy within your infrastructure is coming.
[Image: Collaboration Kit Architecture]
Vaadin Application Architecture with Collaboration Kit
## Core Concepts
To use Collaboration Kit, to get the most out of it, it’s useful to understand some core concepts. These are covered in the following sub-sections.
### Topics
Collaboration between users is managed by collecting data into *topic* instances that are shared by all users interacting with the same part of the application. A topic is similar to a chat room: it has an identifier that’s unique in the context of the application, and members receive all updates related to any topic in which they’re participating.
Topic identifiers are free-form strings that the developer may choose (e.g., "app" or "contract-126-address"). When building a topic for a work item, it’s a good idea for the name of the entity and the entity’s identifier in the topic identifier. For example, if you’re making a form for editing a `Person` entity, and the `Person` has the identifier 120, a good topic name would be "person/120".
### Helpers for Specific Use Cases
Collaboration Kit includes several high-level APIs that address the specific use cases of collaboratively editing a form and having real-time discussions.
`CollaborationBinder` enhances the regular Vaadin `Binder` to share the current value of each field with all other users configured to use the same topic.
`CollaborationAvatarGroup` is a component that shows the avatar of every user who is present in a given topic, for example all users currently viewing or editing the same form.
`CollaborationMessageList` is a component that displays messages submitted with a `CollaborationMessageInput` component in real time.
### Collaboration Managers
Collaboration Managers provides a mid-level API to handle collaborative data for the most common use cases and let developers build their own collaborative logic and custom components:
`PresenceManager` lets you mark user presence in a Topic and subscribe to presence changes. See [Presence Manager documentation](https://vaadin.com/docs/next/tools/collaboration/managers/presence-manager.md) for more information.
`MessageManager` can submit messages to a Topic and subscribe to incoming, new ones. See [Message Manager documentation](https://vaadin.com/docs/next/tools/collaboration/managers/message-manager.md) for more information.
`FormManager` lets you set property values and field highlighting in a form, and to react to changes in them. See [Form Manager documentation](https://vaadin.com/docs/next/tools/collaboration/managers/form-manager.md) for more information.
### Low-Level API
The low-level Topic API allows synchronizing arbitrary data among users. It’s used internally by Collaboration Managers, but can also be used separately to create custom, collaborative user experiences. The entry point to using the Topic API is by opening a `TopicConnection` through `CollaborationEngine::openTopicConnection`.
A topic has multiple named maps and lists which are shared across connections. Each map contains many \ pairs, while a list contains ordered values.
It’s strongly recommended that shared values should be immutable instances. Subscribers are notified only when the shared value is replaced with another instance, but not when the content of an existing value is updated.
For complex values in a map, a conditional replace operation is available to prevent overwriting concurrent modifications to other parts of the shared data.
## Feature Limitations
Collaboration Kit is production-ready and stable. However, some features are still under development, and are not yet available.
The Kit is currently missing support for complex data structures with nested arrays and maps. You should also be aware that topic data isn’t persisted between server restarts. Applications can manually persist topic data and repopulate after a restart if necessary.
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