When you build a Slack app, you’re not just creating features, you’re creating experiences. And every experience needs a place to live. In Slack, those places are called surfaces. A surface is simply a space inside Slack where your app can communicate with users or interact with them. Some surfaces are persistent and always available. Others appear only when needed. Some are built with Block Kit, and others with markdown. They’re all different, but together, they give developers enormous flexibility to design exactly the experience they want. If you’re new to Slack app development, think of surfaces as “rooms” in your app’s virtual house. Each room has a purpose, a mood, and a way people interact inside it. Once you get familiar with these rooms, your app suddenly has so much more creative range. Whether you’re building your first app or expanding an existing one, surfaces are the secret to making something people want to use every day. They’re the foundation that everything else builds on. Once you understand how they work — and how they fit together — it becomes much easier to design interfaces, workflows, and experiences that feel natural inside Slack. And as you start building, it’s helpful to know that surfaces aren’t just UI concepts. Each one is powered by an API that lets your app create, update, and shape the experience. Think of it as the wiring behind each “room” in your Slack app’s house: 

1. Messages use the Conversations API to post updates, format content, add interactive elements, and participate directly in channels and DMs.
2. Modals — along with App Home, which is built from a view — both use the Views API. It’s what lets your app open, update, and manage structured layouts that guide people through focused tasks or personalized dashboards.
3. Canvases use the Canvas API to generate rich, structured documents that stay organized over time — perfect for content people return to and reference over time.
4. Lists rely on the Lists API to create, organize, and update shared work in a way that stays visible, trackable, and actionable.

Each API gives your app a different way to shape how work comes to life inside Slack. And when you know which surface to use, everything you build starts to feel more intentional and intuitive. Let’s walk through every Slack surface, what makes it unique, and when you should use each one.

Messages: The conversational hub

Messages are where your app steps into the flow of work and becomes part of the dialogue. They’re perfect for interactions that are quick, timely, and contextual. Use messages when your app:

• Responds to a command
• Sends an update or alert
• Presents a button, menu, or interactive choice
• Guides someone step-by-step through a process

Messages feel dynamic and collaborative — ideal for moments when your app should join the conversation and move work forward.

Modals: Your app’s pop-up studio

When your app needs someone’s full attention for a short, structured task, modals are the ideal surface. They shine when you want to:

• Request structured input
• Collect details or decisions
• Create a short, guided flow
• Build multi-step forms

Modals take center stage, help users complete something quickly, and then gracefully step aside when the job is done.

App Home: Your app’s personal dashboard

Every app needs a home, a place where a user can return to, reset, and see what matters most. App Home is that space. It’s perfect for:

• Personalized dashboards
• Actionable summaries
• Settings panels
• Shortcuts to common actions

Because every user gets their own version of the Home tab, it becomes a stable and reliable anchor for long-term engagement with your app.

Canvases: Organized information, beautifully presented

Some information deserves a breathing space. A place where it can sit, stay organized, and be revisited. That’s exactly what canvases offer. You can use them for:

• Onboarding guides
• Team instructions
• Project summaries
• Curated resources
• Workflows embedded in context

Canvases give your app a clear, persistent way to share information that users can return to whenever they need it.

Lists: Shared work, structured and visible

Lists help teams organize and collaborate on work inside Slack. Your app can help populate, shape, and update these lists — making them a natural fit for task-based or operational workflows. They’re perfect when your app supports triage, approvals, assignments, or progress tracking. Lists turn work into something concrete, shared, and easy to follow and your app can be right there helping keep everything moving. Lists turn work into something concrete, shared, and easy to follow. And your app can be right there helping keep everything moving.

Split View: Designed for AI experiences

Split View adds a new dimension to Slack apps, especially those powered by AI. It gives people two spaces side-by-side: a conversational side (Chat), and a contextual side (History or supporting content). This makes Split View a great choice for AI assistants, agents, or apps that help users think, explore, or act with deeper context. While each surface works beautifully on its own, the real magic happens when you start combining them. A modal can feed data into a message, a list can power a dashboard in App Home, or an AI agent in Split View can update a canvas with insights. These aren’t just UI choices, they are building blocks for richer, more adaptive workflows.

When to choose each surface

If you want to…	Use
Show a personal dashboard	App Home
Document something long-form	Canvases
Track tasks or items	Lists
Chat or guide in conversation	Messages
Collect structured input	Modals
Build an AI chat experience	Split View

  When you choose the right surface:

• Your users feel like Slack is working with them, not against them
• Your app feels intuitive
• Your workflows feel seamless

As you explore more advanced patterns — like bringing surfaces to life with Block Kit, connecting them through workflows, or using frameworks like Bolt or the Slack CLI — you’ll start to see how these pieces interlock. Surfaces are the “where,” and your app’s logic is the “how.” Put them together, and you can create powerful, intuitive experiences that genuinely support the way people work. Each surface plays a meaningful part, and together they create an experience that feels thoughtful, cohesive, and integrated into the flow of everyday work. When you know when and why to use each one, you unlock the full creative potential of building on Slack.