# Displaying Hotkeys in Your Lit UI

Format a hotkey as a label whenever it appears in a menu, button, tooltip, cheat sheet, or shortcut settings panel. `FormatForDisplayController` has a `format` function that formats chord strings, including physical ones such as `'Mod+[KeyS]'`, chord objects, parsed chords, and sequences. Store the hotkey itself, and format it when you render. A label is for reading, not for registering.

A label depends on the user's platform: `Mod+S` is `⌘ S` on macOS and `Ctrl+S` elsewhere. In the browser, the controller detects the platform. With Lit SSR, set the controller's `platform` from the request. See [Format labels in server-rendered apps](#format-labels-in-server-rendered-apps).

## Format a hotkey

Create a `FormatForDisplayController` as a class field. Its `format` function formats a hotkey:

```ts
import { LitElement, html } from 'lit'
import { customElement } from 'lit/decorators.js'
import { FormatForDisplayController } from '@tanstack/lit-hotkeys'

@customElement('save-button')
class SaveButton extends LitElement {
  private formatForDisplay = new FormatForDisplayController(this)

  render() {
    return html`
      <button>
        Save <kbd>${this.formatForDisplay.format('Mod+S')}</kbd>
      </button>
    `
  }
}
```

The label is `⌘ S` on macOS and `Ctrl+S` on Windows and Linux. The controller fills in two things for you:

- **The platform** from the controller's `platform` option, or the detected platform without one.
- **The user's keyboard layout**, for physical keys, in Chromium browsers. See [Label physical keys for the user's keyboard](#label-physical-keys-for-the-users-keyboard).

Create the controller once, then call `format` anywhere in the element, including in loops and conditions. Options go in its second argument. `format` needs no `this`, so you can put it in a variable. The examples in this guide do, and pass `platform`, so each one has a single result:

```ts
const formatForDisplay = this.formatForDisplay.format

formatForDisplay('Mod+S', { platform: 'mac' }) // '⌘ S'
formatForDisplay('Mod+[KeyS]', { platform: 'mac' }) // '⌘ S'
formatForDisplay({ code: 'KeyS', mod: true }, { platform: 'windows' }) // 'Ctrl+S'
formatForDisplay('Mod+[Digit2]', { platform: 'windows' }) // 'Ctrl+2'
```

The same label can stand for different hotkeys. `Mod+S` follows the character S, and `Mod+[KeyS]` follows the key in the S position. See [Match a key's position instead](../../../guides/sensible-defaults.md#match-a-keys-position-instead). Labels for positions shorten `KeyS` to `S` and `Digit2` to `2`, keep readable numpad labels, and reuse punctuation and special-key symbols. The extra ISO and JIS keys, which have no US key, use their keycap legends: `[IntlBackslash]` shows `\`, `[IntlRo]` shows `\`, and `[IntlYen]` shows `¥`. Formatting doesn't change the stored hotkey or guess the user's keyboard layout.

A `platform` you pass wins over the controller's. On macOS, the label joins modifier symbols with spaces. Windows and Linux use names joined with `+`. macOS orders modifiers as Control, Option, Shift, Command, so `Mod+Shift+S` displays as `⇧ ⌘ S`, while the hotkey itself stays `Mod+Shift+S`.

The function accepts hotkeys only, including single keys such as `'Escape'` and modifiers on their own such as `'Shift'`. A key from a `KeyboardEvent`, such as a held key, can be outside the key types: pass it as `{ key }`.

## Render individual keycaps

Set `parts: true` to get one label per key instead of a joined string:

```ts
const saveHotkey = 'Mod+[KeyS]'
const parts = formatForDisplay(saveHotkey, { platform: 'mac', parts: true })
// ['⌘', 'S'], one label per <kbd>
```

With `parts` omitted or false, the result is a string. A runtime boolean returns `string | string[]`. Parts keep literal plus keys and ignore `separatorToken`.

## Format sequences

Pass a sequence to format each step and join the steps with `sequenceSeparator`, a space by default:

```ts
formatForDisplay(['Mod+[KeyK]', 'C'], { platform: 'mac' }) // '⌘ K C'
formatForDisplay(['G', 'G'], { sequenceSeparator: ' → ' }) // 'G → G'
formatForDisplay(['Mod+[KeyK]', 'C'], { platform: 'mac', parts: true })
// [['⌘', 'K'], ['C']], one array of keycaps per step
```

With `parts: true`, a sequence returns one array per step, so you can render each step as a group of keycaps. To show the steps a user has pressed so far, see [Show sequences in your UI](./sequences#show-sequences-in-your-ui).

## Choose symbols and separators

`useSymbols` accepts a boolean or separate `modifiers` and `keys` settings. Omitted fields default to true. Modifier symbols apply on macOS. Windows and Linux keep modifier names.

```ts
formatForDisplay('Shift+[ArrowUp]', {
  platform: 'mac',
  useSymbols: { modifiers: false, keys: true },
  parts: true,
}) // ['Shift', '↑']

formatForDisplay('Mod+[KeyS]', {
  platform: 'mac', useSymbols: false,
}) // 'Cmd+S'

formatForDisplay('Control++', {
  platform: 'windows', separatorToken: ' · ',
}) // 'Ctrl · +'
```

An empty separator joins labels directly. `undefined` or `null` uses the platform default. `separatorToken` applies within a chord, and `sequenceSeparator` applies between steps.

## Label physical keys for the user's keyboard

A position, such as `[KeyQ]`, has a fallback label for a US keyboard: `Q`. On a French AZERTY keyboard, that key is labeled A. Labels from `FormatForDisplayController` follow the user's keyboard where the browser reports its layout:

```ts
import { LitElement, html } from 'lit'
import { customElement } from 'lit/decorators.js'
import { FormatForDisplayController } from '@tanstack/lit-hotkeys'

@customElement('move-up')
class MoveUp extends LitElement {
  private formatForDisplay = new FormatForDisplayController(this)

  render() {
    // 'W' on QWERTY, 'Z' on AZERTY
    return html`<kbd>${this.formatForDisplay.format('[KeyW]')}</kbd>`
  }
}
```

> [!IMPORTANT]
> **Layout labels work only in Chromium browsers**, such as Chrome and Edge. Firefox and Safari don't report the keyboard layout, so labels there keep the fallback. For `[KeyQ]`, a French AZERTY user sees `A` in Chrome and `Q` in Firefox. In a cross-origin iframe, Chromium browsers also refuse unless the frame has `allow="keyboard-map"`.

- **The layout loads when the first element with a controller connects.** The first render shows the fallback label, and so does server HTML. The label updates when the layout arrives. Later elements get it right after their first render, before the browser paints.
- **Only positions change.** Hotkeys that follow characters, such as `Mod+Q`, already show the right key. Matching and recording never use the layout.
- **The layout is read again when the window regains focus**, because browsers send no event when the user switches layouts. This stops when no element with a controller is connected.

A `KeyboardLayoutController` has the loaded layout, or `null`, as its `value`, for labels you draw yourself, such as an on-screen keyboard. It maps each code to the character the key types without modifiers, such as `KeyQ` to `a`.

The layout comes from `navigator.keyboard.getLayoutMap()`. To never call it, set `keyboardLayout: false` in the controller's options. Lit has no provider, so set it on each controller:

```ts
private formatForDisplay = new FormatForDisplayController(this, {
  keyboardLayout: false,
})
```

A `KeyboardLayoutController` always loads the layout, so don't create one either.

### Supply your own layout

Pass the same kind of map as `layoutMap`, for a layout your app already knows, such as one the user picked in settings:

```ts
const layoutMap = new Map([['KeyQ', 'a']])

formatForDisplay('Mod+[KeyQ]', { platform: 'mac', layoutMap }) // '⌘ A'
formatForDisplay('Mod+Q', { platform: 'mac', layoutMap }) // '⌘ Q'
```

Any object with `get(code): string | undefined` works. A `layoutMap` you pass wins over the loaded layout.

Use `keyLabels` for your own labels, keyed by physical code or by key name:

```ts
formatForDisplay('Mod+[KeyQ]', {
  platform: 'mac', layoutMap, keyLabels: { KeyQ: 'Action' },
}) // '⌘ Action'
```

`keyLabels` wins over a layout entry, which wins over the fallback label. Layout entries get normal letter casing and key symbols, and missing or empty entries fall back. All of these options affect display only. `keyLabels` works anywhere, including on the server.

## Format labels in server-rendered apps

With Lit SSR (`@lit-labs/ssr`), the server doesn't know the user's platform. Without one, a label rendered on the server uses `'linux'`, so a Mac user gets `Ctrl+S` in the server's HTML. Hydration doesn't fix it: Lit expects the browser's first render to match the server's HTML, and keeps the server's text. To render the right label from the start:

1. Give the element a `platform` property, and pass the controller a function that reads it. Lit has no provider, so the controller's options are where the platform goes.
2. Read the request's `User-Agent` header on the server, and set the element's `platform` attribute to `detectPlatform(userAgent)`.

```ts
import { LitElement, html } from 'lit'
import { customElement, property } from 'lit/decorators.js'
import { FormatForDisplayController } from '@tanstack/lit-hotkeys'
import type { HotkeyPlatform } from '@tanstack/lit-hotkeys'

@customElement('save-button')
class SaveButton extends LitElement {
  @property() platform?: HotkeyPlatform

  // The function is read for each label, so it follows the property
  private formatForDisplay = new FormatForDisplayController(this, () => ({
    platform: this.platform,
  }))

  render() {
    return html`
      <button>
        Save <kbd>${this.formatForDisplay.format('Mod+S')}</kbd>
      </button>
    `
  }
}
```

On the server, set the attribute:

```ts
import { render } from '@lit-labs/ssr'
import { html } from 'lit'
import { detectPlatform } from '@tanstack/lit-hotkeys'

const platform = detectPlatform(userAgent)
const result = render(html`<save-button platform=${platform}></save-button>`)
```

Every label in the element then uses the property's platform. A `platform` passed to `format` wins over it.

The attribute is part of the server's HTML, so the element reads the same `platform` when it upgrades in the browser. Pass it on to child elements that show labels, such as `.platform=${this.platform}`. An element that renders only in the browser needs no `platform`: the controller detects it.

Labels have no keyboard layout on the server or in an element's first render, so they hydrate unchanged. See [Label physical keys for the user's keyboard](#label-physical-keys-for-the-users-keyboard).

Pages rendered this way depend on the request's `User-Agent` header. If a CDN or another shared cache stores them, it can serve one user's labels, and the platform that `Mod` resolves to, to other users. Keep these pages out of shared caches, or add the platform to the cache key. `Vary: User-Agent` also works, but it splits the cache into many small entries.

## Format outside an element

`FormatForDisplayController` needs a host element. Some code that builds labels has none, such as a helper function, a test, or a plain module. There, call the plain `formatForDisplay` function and pass the platform yourself:

```ts
import { formatForDisplay } from '@tanstack/lit-hotkeys'

formatForDisplay('Mod+S', { platform }) // '⌘ S' when platform is 'mac'
```

The plain function takes the same options as the controller's `format`. It doesn't read a controller's options, and it uses only the `layoutMap` you pass. Without a `platform`, it detects one in the browser and uses `'linux'` on a server. To give it the user's layout, call `loadKeyboardLayout()` in the browser, and read the layout from `getKeyboardLayoutStore()`.

The export is marked deprecated so that your editor points element code to the controller. Outside an element, it is the function to use.

## Parse, compare, and store hotkeys

`parseHotkey` returns each chord's key, as either a logical `key` or a physical `code`, plus its modifiers with `Mod` resolved. Check which one you have before reading it:

```ts
import { normalizeHotkey, parseHotkey } from '@tanstack/lit-hotkeys'

const parsed = parseHotkey('Mod+[KeyS]', 'mac')
if (parsed.code !== undefined) {
  console.log(parsed.code) // 'KeyS'; parsed.key is undefined
}
const stored = normalizeHotkey(parsed, 'mac') // 'Mod+[KeyS]'
```

A parsed chord's modifiers are already resolved for one platform. To store it as a hotkey that works on every platform, normalize it with that same platform, as above. `normalizeHotkey` also accepts chord strings, chord objects, and sequences. Store hotkeys, never display labels. [Write a chord as a string or an object](./hotkeys#write-a-chord-as-a-string-or-an-object) covers the forms a hotkey can take.

`areHotkeysEqual(a, b)` compares chords or sequences after resolving modifiers, so `Mod+S` equals `Meta+S` on macOS. Sequences compare step by step. `isHotkeySequence` narrows a `Hotkey` to a sequence, and `simplifyHotkey` turns a one-step sequence into its chord.

Use `validateHotkey` when you accept a hotkey from somewhere else, such as a settings file. It returns `valid`, `errors`, and `warnings`. Each error or warning has a `reason` code, such as `'unknown-modifier'`, the `part` it's about, and for a sequence, the index of the `step`. The library sends no text, so write your own messages for users. The devtools describe each problem in the details of a hotkey. It can't promise that the browser or operating system delivers the shortcut. To check hotkeys as users record them, see [Validate and check conflicts](./custom-hotkey-recording#validate-and-check-conflicts).

For a full list of your app's shortcuts, see [Cheat Sheet UI Helpers](./cheat-sheet-ui-helpers).