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 a hotkey#

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

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.

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:

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. 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:

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:

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.

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.

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:

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>`
  }
}

• 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:

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:

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:

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).

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:

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.

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:

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:

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 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.

For a full list of your app's shortcuts, see Cheat Sheet UI Helpers.