You are writing in one language, you hit a phrase you don't have, so you type it in a language you do have and carry on. Tap the Space bar three times and the line becomes the language you were writing in.
这个功能 should be 很简单 → This feature should be very simple
Je voudrais 预约 une réunion → Je voudrais réserver une réunion
明日の会議を 预约 したい → 明日の会議を予約したい
It works in any app that macOS lets it read — a text editor, a browser field, a chat box, a terminal. The language it writes is yours to set: TypeSwitch is not built around one language pair.
Read this before installing. TypeSwitch needs Accessibility and Input Monitoring permission, which means it can see everything you type and read the text field you are focused on. It sends the one line it rewrites, to the endpoint you configure, and nothing else. Read How does it work? and the source before you grant that.
Because the interruption is the problem. Switching input method, hunting for the word, switching back, and rereading the sentence costs more than the word was worth. TypeSwitch lets you leave the gap in whatever language reaches your fingers first, and repair it without breaking stride.
| Area | TypeSwitch behavior |
|---|---|
| What it rewrites | The selection, or the line the cursor is on |
| Target language | Whatever you type into a field, not a fixed pair |
| Where it works | Any app whose text macOS exposes, terminals included |
| Model | Your endpoint, your key, your system prompt, all editable |
| Background activity | No login item, daemon, telemetry, or analytics |
| Interface | English and Simplified Chinese, following your system |
- macOS 14 or later, Apple silicon
- An API key for any service that speaks the OpenAI chat-completions format
- Xcode 16 or later, only if you build it yourself
-
Download
TypeSwitch-<version>.dmgand its.sha256from the latest release. -
Verify the download:
shasum -a 256 -c TypeSwitch-*.dmg.sha256 -
Open the DMG, drag TypeSwitch to Applications, and open it.
The release is signed with a Developer ID certificate and notarized by Apple, so it opens without a Gatekeeper detour.
On first launch TypeSwitch asks for two grants in System Settings → Privacy & Security:
- Accessibility — to read the line you are on and write the rewrite back
- Input Monitoring — to notice the trigger keystrokes
It only watches for the trigger and never modifies a keystroke on its way to the app you are typing in. Grant both and it starts working; no relaunch needed.
Open Settings → AI service, pick a provider or type any OpenAI-compatible address, and paste your key. It is stored in your login keychain and sent only to that address. Nothing is bundled with the app.
Select some text and trigger, and TypeSwitch rewrites the selection. Select nothing and it rewrites the line your cursor is on.
Trigger — click the key field and press whatever key you want, then set how many taps and how close together. The default is three taps of Space within 0.30 seconds. A modifier key (⇧, ⌘, ⌥, ⌃, left and right are distinct) types nothing, so it leaves no stray characters in the line; an ordinary key does, and the extra characters get replaced along with the line.
macOS turns two quick spaces into a period, which lands in the middle of a Space-triggered rewrite. The Settings window has a switch for that system setting, so you can turn it off without leaving the app.
AI service — the endpoint, the model, and your key. Presets for DeepSeek,
OpenAI, Moonshot, and a local Ollama fill the first two in; anything else that
speaks POST /chat/completions works if you type the address yourself.
Output language — what your text is rewritten into. Default English. Any language the model knows works.
Rewrite instructions — the system prompt, shown in full and editable.
{{language}} is replaced with the output language above. Clear the field to go
back to the built-in one.
Menu bar icon — can be hidden. With it hidden, opening TypeSwitch again brings back the Settings window.
Trigger. A CGEventTap in listen-only mode counts taps of your trigger key.
Listen-only matters: a tap that swallowed the Space would break candidate
selection in every input method, so TypeSwitch never modifies the event stream.
Key repeats are filtered out, so holding the key down does not trigger it.
Reading and writing. The Accessibility API first — the focused element's value and selected range. Some apps report a successful write and apply nothing, so the write is read back to confirm; if it did not take, TypeSwitch falls back to synthesizing ⌘C/⌘V, saving and restoring your pasteboard around it.
Because the tap does not modify events, the trigger keystrokes are still on their way to the app when the tap fires. TypeSwitch waits for them to land before reading, and re-reads the text at write time to confirm it has not changed. If focus moved or the text changed, it writes nothing.
Rewriting. One non-streaming POST /chat/completions. Round-trip is about
0.6s on DeepSeek with reasoning off. The result is written back in one edit, so
⌘Z undoes it in apps that support undo.
git clone https://github.com/max1874/type-switch.git
cd type-switch
make app
open build/TypeSwitch.appThe project signs ad-hoc by default, so it builds with no Apple developer
account. The catch is that macOS ties Accessibility and Input Monitoring grants
to the signature, and an ad-hoc signature changes on every build — so you
re-approve TypeSwitch each time you rebuild. If you have a developer account,
cp Config/Local.xcconfig.example Config/Local.xcconfig, put your team ID in it,
and the grants stick. That file is gitignored.
make app # Build TypeSwitch.app into build/
make release # Signed, notarized, stapled DMG — maintainers only
make clean # Remove build/make release runs on a maintainer's own machine rather than in CI, so the
Developer ID certificate never leaves it. It needs notarization credentials
stored once:
xcrun notarytool store-credentials TypeSwitch \
--key <path-to-AuthKey.p8> --key-id <key-id> --issuer <issuer-id>- It triggers everywhere, including terminals and code editors, where the line it picks up may be a shell prompt rather than prose. There is no per-app allowlist yet.
- Only the DeepSeek path is tested. The OpenAI, Moonshot, and Ollama presets are the documented shapes of those APIs, not verified requests.
- Undo depends on the app. Where the pasteboard fallback is used, ⌘Z behaves the way a paste does in that app.
- Apple silicon only in the released build.
The text of one line, or one selection, goes to the endpoint you configured, when you trigger it. Nothing else leaves your machine — no telemetry, no analytics, no other network calls. Your key lives in your login keychain. The app is not sandboxed, because a sandboxed app cannot create an event tap or read another app's text.
MIT © 2026 Max