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Messages (Msgs) are the events that drive your Bubble Tea application. Every interaction, timer tick, HTTP response, and system event becomes a message that flows through your Update method.

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What Are Messages?

From tea.go:47-49: 
// Msg contain data from the result of a IO operation. Msgs trigger the update
// function and, henceforth, the UI.
type Msg = uv.Event
A Msg can be any type. This flexibility lets you define custom messages that perfectly match your application’s needs.

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The Message Flow

  1. Something happens (key press, timer, etc.)
  2. Bubble Tea wraps it in a Msg
  3. Your Update method receives it
  4. You return an updated model
  5. Bubble Tea calls View and renders

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Built-in Message Types

Bubble Tea provides several built-in message types for common events.

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Keyboard Messages

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KeyPressMsg

The most common message - sent when a key is pressed. From key.go:190-221: 
// KeyPressMsg represents a key press message.
type KeyPressMsg Key

func (k KeyPressMsg) String() string
func (k KeyPressMsg) Keystroke() string
func (k KeyPressMsg) Key() Key
Usage: 
func (m model) Update(msg tea.Msg) (tea.Model, tea.Cmd) {
    switch msg := msg.(type) {
    case tea.KeyPressMsg:
        // Method 1: String matching (simpler)
        switch msg.String() {
        case "ctrl+c", "q":
            return m, tea.Quit
        case "up", "k":
            m.cursor--
        case "enter":
            return m, m.submit()
        }
        
        // Method 2: Key code matching (more precise)
        key := msg.Key()
        switch key.Code {
        case tea.KeyEnter:
            return m, m.submit()
        case tea.KeyUp:
            m.cursor--
        }
    }
    return m, nil
}

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Key Structure

From key.go:302-343: 
type Key struct {
    // Text contains the actual characters received
    Text string
    
    // Mod represents modifier keys (Ctrl, Alt, Shift, etc.)
    Mod KeyMod
    
    // Code represents the key pressed
    Code rune
    
    // ShiftedCode is the shifted key (e.g., 'A' when shift+a)
    ShiftedCode rune
    
    // BaseCode is the key on a standard PC-101 layout
    BaseCode rune
    
    // IsRepeat indicates if key is being held down
    IsRepeat bool
}
Common Key Codes: 
tea.KeyEnter     // Enter/Return key
tea.KeySpace     // Space bar
tea.KeyBackspace // Backspace
tea.KeyTab       // Tab
tea.KeyEsc       // Escape

// Arrow keys
tea.KeyUp
tea.KeyDown
tea.KeyLeft
tea.KeyRight

// Function keys
tea.KeyF1 through tea.KeyF63

// Special keys
tea.KeyHome
tea.KeyEnd
tea.KeyPgUp
tea.KeyPgDown
tea.KeyDelete
tea.KeyInsert
See key.go:16-188 for the complete list.

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KeyReleaseMsg

Sent when a key is released (requires keyboard enhancements). 
case tea.KeyReleaseMsg:
    fmt.Println("Key released:", msg.String())

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Mouse Messages

From mouse.go:44-51: 
// MouseMsg represents a mouse message. This is a generic mouse message that
// can represent any kind of mouse event.
type MouseMsg interface {
    fmt.Stringer
    Mouse() Mouse
}

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Mouse Structure

type Mouse struct {
    X, Y   int          // Position (0-based from top-left)
    Button MouseButton  // Which button
    Mod    KeyMod       // Modifier keys held
}

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Mouse Button Constants

From mouse.go:29-42: 
tea.MouseNone        // No button
tea.MouseLeft        // Left button
tea.MouseMiddle      // Middle button
tea.MouseRight       // Right button
tea.MouseWheelUp     // Scroll up
tea.MouseWheelDown   // Scroll down
tea.MouseWheelLeft   // Scroll left
tea.MouseWheelRight  // Scroll right
tea.MouseBackward    // Browser back button
tea.MouseForward     // Browser forward button

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Mouse Event Types

case tea.MouseClickMsg:
    m := msg.Mouse()
    if m.Button == tea.MouseLeft {
        fmt.Printf("Clicked at (%d, %d)\n", m.X, m.Y)
    }
Mouse events require enabling mouse mode in your view:
func (m model) View() tea.View {
    v := tea.NewView(m.render())
    v.MouseMode = tea.MouseModeAllMotion  // Enable all mouse events
    return v
}

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Window Messages

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WindowSizeMsg

Sent when the terminal is resized or when the program starts. 
case tea.WindowSizeMsg:
    m.width = msg.Width
    m.height = msg.Height
    // Resize child components
    m.viewport.Width = msg.Width
    m.viewport.Height = msg.Height - 2
You’ll receive a WindowSizeMsg immediately when your program starts, giving you the initial terminal dimensions.

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System Messages

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QuitMsg

Signals the program should quit. From tea.go:534-541: 
// QuitMsg signals that the program should quit.
type QuitMsg struct{}

// Quit is a special command that tells the Bubble Tea program to exit.
func Quit() Msg {
    return QuitMsg{}
}
Usage: 
case tea.KeyPressMsg:
    if msg.String() == "q" {
        return m, tea.Quit  // Returns a command that sends QuitMsg
    }

case tea.QuitMsg:
    // Handle cleanup before quitting
    return m, nil

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InterruptMsg

Sent when Ctrl+C is pressed (when not caught as a key press). From tea.go:560-572: 
// InterruptMsg signals the program should interrupt.
type InterruptMsg struct{}

func Interrupt() Msg {
    return InterruptMsg{}
}

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SuspendMsg / ResumeMsg

Sent when the program is suspended (Ctrl+Z) and resumed. From tea.go:543-558: 
// SuspendMsg signals the program should suspend.
type SuspendMsg struct{}

func Suspend() Msg {
    return SuspendMsg{}
}

// ResumeMsg can be listened to do something once a program is resumed back
// from a suspend state.
type ResumeMsg struct{}
Example: 
case tea.SuspendMsg:
    // Save state before suspending
    m.saveState()
    return m, tea.Suspend

case tea.ResumeMsg:
    // Refresh after resuming
    return m, m.fetchLatestData()

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Color and Terminal Info

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ColorProfileMsg

Sent when the terminal’s color capabilities are detected. 
case tea.ColorProfileMsg:
    m.profile = msg.Profile
    // Adjust colors based on capabilities

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Custom Messages

The real power of messages is defining your own types.

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Defining Custom Messages

// Simple message with no data
type tickMsg time.Time

// Message with data
type userLoadedMsg struct {
    user User
}

// Error message
type errMsg struct {
    err error
}
By convention, custom message types end with Msg, but this isn’t required.

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Using Custom Messages

func (m model) Update(msg tea.Msg) (tea.Model, tea.Cmd) {
    switch msg := msg.(type) {
    
    case tickMsg:
        m.lastTick = time.Time(msg)
        return m, tick()  // Schedule next tick
    
    case userLoadedMsg:
        m.user = msg.user
        m.loading = false
        return m, nil
    
    case errMsg:
        m.err = msg.err
        m.loading = false
        return m, nil
    }
    return m, nil
}

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Creating Custom Messages from Commands

Commands return messages: 
func fetchUser(id int) tea.Cmd {
    return func() tea.Msg {
        user, err := api.GetUser(id)
        if err != nil {
            return errMsg{err}
        }
        return userLoadedMsg{user}
    }
}

// Use in Update
case tea.KeyPressMsg:
    if msg.String() == "enter" {
        m.loading = true
        return m, fetchUser(m.selectedID)
    }
See examples/simple/main.go:73-78 for a real example.

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Message Patterns

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The Tick Pattern

type tickMsg time.Time

func tick() tea.Cmd {
    return tea.Tick(time.Second, func(t time.Time) tea.Msg {
        return tickMsg(t)
    })
}

func (m model) Update(msg tea.Msg) (tea.Model, tea.Cmd) {
    switch msg.(type) {
    case tickMsg:
        m.counter++
        return m, tick()  // Schedule next tick
    }
    return m, nil
}

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The Request/Response Pattern

// Request
type loadDataMsg struct{}

// Responses
type dataLoadedMsg struct {
    data []Item
}
type dataErrorMsg struct {
    err error
}

func loadData() tea.Cmd {
    return func() tea.Msg {
        data, err := fetchData()
        if err != nil {
            return dataErrorMsg{err}
        }
        return dataLoadedMsg{data}
    }
}

​
The State Machine Pattern

type state int

const (
    stateLoading state = iota
    stateReady
    stateError
)

type stateChangeMsg struct {
    newState state
}

func (m model) Update(msg tea.Msg) (tea.Model, tea.Cmd) {
    switch msg := msg.(type) {
    case stateChangeMsg:
        m.state = msg.newState
        switch msg.newState {
        case stateLoading:
            return m, loadData()
        case stateReady:
            return m, nil
        case stateError:
            return m, nil
        }
    }
    return m, nil
}

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Best Practices

Always use type switches to handle messages:
// Good
switch msg := msg.(type) {
case tea.KeyPressMsg:
    // msg is now KeyPressMsg
}

// Bad - loses type information
switch msg.(type) {
case tea.KeyPressMsg:
    // msg is still tea.Msg
}
Always have a default case that returns the model unchanged:
func (m model) Update(msg tea.Msg) (tea.Model, tea.Cmd) {
    switch msg := msg.(type) {
    case myMsg:
        // Handle
    default:
        // Don't drop messages you don't recognize
    }
    return m, nil
}
Messages should be plain data - no methods, no behavior:
// Good
type userLoadedMsg struct {
    user User
}

// Bad - too much behavior
type userLoadedMsg struct {
    user User
}
func (m userLoadedMsg) Process() { /* ... */ }
Add comments explaining when and why messages are sent:
// tickMsg is sent every second to update the countdown timer.
type tickMsg time.Time

// dataLoadedMsg is sent when the API request completes successfully.
type dataLoadedMsg struct {
    items []Item
}

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Next Steps

Commands

Learn how to create commands that generate messages

Model

Understand how messages update your model

Views

See how model updates trigger rendering

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