# Displaying Hotkeys in Your Octane UI

> [!NOTE]
> Showing hotkey labels on the page is one of the few parts of TanStack Hotkeys that needs extra care in server-rendered apps. The server doesn't know the user's operating system, so a label it renders can differ from the label the browser renders, which causes a hydration error. The library has helpers that prevent this. See [Format labels in server-rendered apps](#format-labels-in-server-rendered-apps).

Use `formatForDisplay` whenever a hotkey appears in a menu, button, tooltip, cheat sheet, or shortcut settings panel. It accepts 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. Pick the API by where your labels render:

| Where labels render | Use |
| --- | --- |
| Only in the browser, such as a Vite single-page app | `formatForDisplay(hotkey)` |
| On the server, then hydrated | `useFormatForDisplay()`, with the provider's `platform` set from the request. See [Format labels in server-rendered apps](#format-labels-in-server-rendered-apps) |
| In a static or prerendered page | `formatForDisplay` inside a client-only wrapper. See [Static and prerendered pages](#static-and-prerendered-pages) |
| Anywhere, for a platform you already know | `formatForDisplay(hotkey, { platform })` |

## Format a hotkey

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

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. Formatting doesn't change the stored hotkey or guess the user's keyboard layout.

Omit `platform` to detect it in the browser. 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`.

`formatForDisplay` 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.

## Supply layout labels

A position, such as `[KeyQ]`, gets a fallback label that may differ from the character printed on the user's keyboard. Pass an already-resolved `layoutMap` to label positions for a known layout:

```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, including a browser `KeyboardLayoutMap`. Formatting stays synchronous. Your app owns loading, errors, and refreshing the map: render fallback labels while it loads, then pass the resolved map on the next render. The library never requests it. Hotkeys that follow characters ignore `layoutMap`.

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.

The browser's `KeyboardLayoutMap` exists only in the browser, and it loads after the page renders. In a server-rendered app, render fallback labels first and pass the map once it loads, as above. The first render then matches the server's HTML. `keyLabels` works anywhere, including on the server.

## Format labels in server-rendered apps

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 and `⌘ S` once Octane hydrates, with a hydration mismatch. To render the right label from the start:

1. Read the request's `User-Agent` header on the server, and pass `detectPlatform(userAgent)` as the provider's `platform`.
2. Format labels with `useFormatForDisplay()` instead of `formatForDisplay`.

```tsx
import { HotkeysProvider, detectPlatform } from '@tanstack/octane-hotkeys'

<HotkeysProvider defaultOptions={{ platform: detectPlatform(userAgent) }}>
  <App />
</HotkeysProvider>
```

```tsx
import { useFormatForDisplay } from '@tanstack/octane-hotkeys'

function Toolbar() @{
  // Call it at the top level of the component, like any hook
  const format = useFormatForDisplay()

  <ul>
    @for (const command of commands; key command.id) {
      <li>
        {command.name} <kbd>{format(command.hotkey)}</kbd>
      </li>
    }
  </ul>
}
```

`useFormatForDisplay` returns a function with the same options as `formatForDisplay`. Call the hook once at the top level of the component, then call the function anywhere, including in loops and conditions. A `platform` passed to the function wins over the provider's.

In the browser, `detectPlatform()` reads the browser's own `navigator`, so the server and the browser get the same platform for practically every user. The provider's `platform` is also the default platform for hotkeys and recorders inside it. An inner provider inherits it.

Without a provider `platform`, `useFormatForDisplay` renders `'linux'` labels on the server and during hydration, then switches to the browser's platform without a hydration error. Mac users see `Ctrl+S` until Octane hydrates. Set the provider's `platform` to avoid that.

The provider must render on the server too, so wrap your app in it where the request is available, as shown for each setup below.

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.

### TanStack Start

`@octanejs/tanstack-start` runs TanStack Start with Octane. `createIsomorphicFn` reads the request header on the server and the browser's `navigator` in the browser, so no loader is needed:

```tsx
// src/routes/__root.tsrx
import { Outlet } from '@octanejs/tanstack-router'
import { createIsomorphicFn } from '@octanejs/tanstack-start'
import { getRequestHeader } from '@octanejs/tanstack-start/server'
import { HotkeysProvider, detectPlatform } from '@tanstack/octane-hotkeys'

const getPlatform = createIsomorphicFn()
  .server(() => detectPlatform(getRequestHeader('user-agent')))
  .client(() => detectPlatform())

function RootLayout() @{
  <HotkeysProvider defaultOptions={{ platform: getPlatform() }}>
    <Outlet />
  </HotkeysProvider>
}
```

Pass `RootLayout` as the `component` of the root route.

### Astro

With `@octanejs/astro`, each Octane island is its own Octane app, so render the provider inside the island and pass the platform from the page. The page must render on demand to have a request: add `export const prerender = false`, or use `output: 'server'`.

```astro
---
// src/pages/index.astro
import { detectPlatform } from '@tanstack/octane-hotkeys'
import { Shortcuts } from '../components/Shortcuts.tsrx'

export const prerender = false
const platform = detectPlatform(Astro.request.headers.get('user-agent'))
---

<Shortcuts client:load platform={platform} />
```

```tsx
// src/components/Shortcuts.tsrx
import { HotkeysProvider } from '@tanstack/octane-hotkeys'
import type { HotkeyPlatform } from '@tanstack/octane-hotkeys'

export function Shortcuts({ platform }: { platform: HotkeyPlatform }) @{
  <HotkeysProvider defaultOptions={{ platform }}>
    <CheatSheet />
  </HotkeysProvider>
}
```

The [Astro example](../examples/useFormatForDisplay-astro) shows this setup.

### Your own server

Render your app with `renderToString` from `octane/server`, and pass the platform as a prop. In the browser, `detectPlatform()` returns the same platform, so `hydrateRoot` gets the same props:

```tsx
// src/App.tsrx
import { HotkeysProvider } from '@tanstack/octane-hotkeys'
import type { HotkeyPlatform } from '@tanstack/octane-hotkeys'

export function App({ platform }: { platform: HotkeyPlatform }) @{
  <HotkeysProvider defaultOptions={{ platform }}>
    <Toolbar />
  </HotkeysProvider>
}
```

```ts
// src/entry-server.ts
import { renderToString } from 'octane/server'
import { detectPlatform } from '@tanstack/octane-hotkeys'
import { App } from './App.tsrx'

export function render(request: Request) {
  const platform = detectPlatform(request.headers.get('user-agent'))
  return renderToString(App, { platform }) // { html, css }
}
```

```ts
// src/entry-client.ts
import { hydrateRoot } from 'octane'
import { detectPlatform } from '@tanstack/octane-hotkeys'
import { App } from './App.tsrx'

hydrateRoot(document.getElementById('app')!, App, { platform: detectPlatform() })
```

Put `css` in the page's `<head>` and `html` in the element you hydrate. `render` takes a Fetch API `Request`. In Express, pass `req.headers['user-agent']` to `detectPlatform` instead. Octane's [server-side rendering guide](https://github.com/octanejs/octane/blob/main/docs/ssr.md) covers compiling the server build and streaming.

The [server rendering example](../examples/useFormatForDisplay-server) shows this setup.

### Render a label only in the browser

To skip server rendering for a label instead, render it after hydration. In the browser, plain `formatForDisplay` detects the platform:

```tsx
import { useSyncExternalStore } from 'octane'
import { formatForDisplay } from '@tanstack/octane-hotkeys'

const subscribe = () => () => {}

function SaveShortcut() @{
  const hydrated = useSyncExternalStore(subscribe, () => true, () => false)

  @if (hydrated) {
    <kbd>{formatForDisplay('Mod+S')}</kbd>
  } @else {
    <kbd>{' '}</kbd>
  }
}
```

Framework wrappers do the same: `<ClientOnly>` from `@octanejs/tanstack-router`, or `client:only="octane"` on an Astro island. A fallback with the label's width keeps the layout from shifting.

### Static and prerendered pages

A page rendered at build time has no request and no user, so neither `formatForDisplay` nor `useFormatForDisplay` can know the platform. This includes prerendered routes in TanStack Start, Astro's default static output, and pages rendered with `prerender` from `octane/static`. Render platform-specific labels in a client-only wrapper, as above. `useFormatForDisplay` without a provider `platform` also works there: it shows `'linux'` labels until hydration, then switches.

### Development warning

In development, formatting a label on the server without a platform logs a warning once. Without a platform, the server renders `'linux'` labels, so users on macOS and Windows get a different label after hydration. If you develop on Linux, you won't see the problem yourself. The warning names the missing setting. It isn't included in production builds.

## 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 { formatForDisplay, normalizeHotkey, parseHotkey } from '@tanstack/octane-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]'
formatForDisplay(stored, { platform: 'windows' }) // 'Ctrl+S'
```

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`, and names the failing step of a sequence. 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).

Try these options together with the format toggles in the [server-rendered cheat sheet example](../examples/useFormatForDisplay-astro). For a full list of your app's shortcuts, see [Cheat Sheet UI Helpers](./cheat-sheet-ui-helpers).