Running ChatGPT in Japanese on a Mac, and where the setting lives

Wanting ChatGPT in Japanese sounds like one request, and it is really three that pull in different directions. The menus and system text can be Japanese, the replies can be Japanese, and typing Japanese into the box can be comfortable or awkward depending on which window it is. Those three are controlled in different places, and only one of them has a documented switch. Getting them confused is why a change that looks correct produces an interface that reverts, or a Japanese interface that keeps answering in English.

Three things are being called language here

The first is the interface language: the sidebar labels, the settings screens, the buttons. This is a setting with a defined list of supported values.

The second is the reply language, which is not that setting. What comes back is driven by the conversation, by any saved instructions, and by the language of the question itself. Switching the interface to Japanese does not oblige the model to answer in Japanese, and leaving the interface in English does not stop it from answering in Japanese. Anyone whose real complaint is that answers arrive in the wrong language should be editing custom instructions, not the language dropdown.

The third is input. Composing Japanese means an input method sits between the keyboard and the text box, converting kana into kanji, and the send key has to coexist with the confirm key. This is a property of the window, not of the account, which is why the same conversation feels different in a browser tab, in the desktop app, and in a standalone window built from the site.

Deciding which of the three is the actual problem takes thirty seconds and saves an hour. The rest of this article deals with the first and the third, since those are the ones that depend on which application the reader opens.

The interface language follows the browser unless told otherwise

OpenAI's help page on language settings states the default behaviour plainly: when ChatGPT is accessed on a browser or a mobile device, the browser or device language is detected automatically and ChatGPT's language is updated to match, for supported languages. Chrome's language preference is described as findable at chrome://settings/languages.

That single sentence explains most of the confusion reported around this. A Mac whose system language is English, running a browser whose preferred language is English, will serve an English interface even to someone who only ever types Japanese. Nothing is broken. The detection is doing what it says.

The manual switch is documented in two places, and only two. In a browser, it is the profile icon, then Settings, then General, then Language, choosing from the dropdown. In the mobile app, it is the sidebar, then the profile icon at the bottom, then Language under App. The page notes that the language setting can only be changed while signed in.

The supported list runs from Albanian to Vietnamese and contains 59 entries. Japanese is on it, so this is not a case of partial support or a machine translated interface appearing where a human translated one should be.

There is a detail worth noticing about that documentation. The steps are written for the browser and for the mobile app. The desktop application is not given its own procedure. For a reader who wants deterministic control over the interface language, that omission is a reason to keep the browser in the picture rather than an argument against the desktop app.

Where the desktop app fits, and the line it draws

The official macOS app is a real option, and it has a hardware requirement that ends the discussion on some machines. OpenAI states the system requirements as macOS 14 and either Apple Silicon, M1 or better, or an Intel processor. The download page detects the processor and serves the matching installer.

macOS 14 excludes a good number of machines that are otherwise perfectly capable of running a chat interface, since Sonoma's compatibility list begins with 2018 models. On a Mac that tops out at Ventura, the question of how to get a Japanese interface in the desktop app does not arise, because there is no desktop app to configure. Chrome states macOS 13 and up as its own Mac requirement, so a browser based window is available on machines the official app cannot reach.

There is a second reason the browser stays relevant even where the app installs. As of July 9 the desktop app was replaced by a version combining Chat, Work and Codex, and the previous macOS app was renamed ChatGPT Classic and continues to be supported. Instructions written before that date describe a different piece of software, which is the usual explanation when a menu item in a Japanese language guide cannot be found.

	Browser tab	Official desktop app	Standalone window from the site
Interface language switch documented	Yes, Settings, General, Language	Not documented separately	Yes, through the browser it is built from
Detected from	Browser preferred language	Not stated	The browser profile it uses
Minimum macOS	Browser's requirement, 13 for Chrome	14	Browser's requirement
Own Dock icon	No	Yes	Yes
Global hotkey overlay	No	Yes, Option and Space by default	No
Two accounts side by side	Separate profiles	One at a time	One bundle each

Why the interface keeps reverting

Reports of a language setting that does not stick usually trace back to the documented rule rather than to a fault, and there are three common shapes.

The first is a signed out session. The help page states that the language setting can only be updated while signed in. Anything opened in a private window, or in a browser that has cleared its cookies, falls back to detection, which means it follows the browser's preferred language again. If the browser is set to English, the interface will be English every time that window is opened, no matter how many times the dropdown was changed elsewhere.

The second is more than one browser profile. Detection reads the preferred language of the profile in use, so a work profile created from a default English installation behaves differently from a personal profile where Japanese was added at the top of the list. The account is the same, the interface is not. Checking chrome://settings/languages in the profile that is actually open, rather than in the one that happens to be in front, resolves this in a few seconds.

The third is order rather than presence. A browser language list can contain Japanese without Japanese being first, and the first entry is what gets sent. Adding the language is only half the change. Moving it to the top of the list is the half that takes effect.

The reliable sequence is to fix the browser preference first, reload, and only then use the in product dropdown if the result is still wrong. Doing it in the other order means the dropdown is fighting the detection on every fresh session, and the detection wins whenever the session is not signed in.

There is a related benefit to settling this before building anything. A standalone window built from a browser profile carries that profile's language preference with it, so a profile fixed today produces a correctly configured window tomorrow. A profile left in an inconsistent state produces a window that behaves inconsistently, and diagnosing it afterwards is harder because the browser's settings screens are no longer one click away.

Keeping one window in Japanese and another in English

The detection behaviour has a practical use once it is understood as a rule rather than a nuisance. Since the interface follows the browser's preferred language, the interface language becomes a property of the browser profile rather than of the machine.

That makes a split setup possible without fighting the system language. One browser profile with Japanese at the top of its language list, one with English, and a separate application window built from each. The Japanese window opens with Japanese menus, the English one with English menus, and both are signed in to whichever account belongs to them because the profiles keep separate cookies.

This is the arrangement people usually want when a personal account and a company account are both in play, or when screenshots have to be produced in one language while daily work happens in the other. Doing it with browser tabs means remembering which window is which. Doing it with two named application bundles means reading the Dock. The Features page describes what a bundle carries over from the browser it is built on, and the Guide covers the build itself.

One caveat belongs here. A tool that turns a site into a standalone Mac app does not add a language selector of its own. It inherits whatever the underlying browser profile is set to, which is precisely why the setting has to be made in the browser first and verified before the bundle is built.

The typing test to run before committing

Interface language is easy to check and easy to change. Input behaviour is neither, and it is the thing that actually determines whether a window is pleasant to use in Japanese all day.

Run this test in whichever window is being considered. Start typing a Japanese sentence, leave the conversion uncommitted, and press the send key. In some web chat interfaces the keystroke that confirms a conversion is also the keystroke that submits the message, which sends half finished text. Then try the opposite: check whether a deliberate line break inside a long prompt is possible without submitting. Then check that the composition candidates window appears in the right place rather than at the corner of the screen.

Three keystrokes, three answers, and they are more decisive than any feature list. A window that submits mid conversion will be abandoned within a week no matter how good its icon is.

The reason a standalone window built from an installed browser tends to behave here is that the input handling is the browser's, not a reimplementation. A tool that borrows the Chromium browser already on the machine inherits its input method handling along with its extensions and its signed in state. That is a design consequence rather than a feature, but it is the one that matters for anyone typing Japanese into the box hundreds of times a day. The Supported services list gives a sense of how many other everyday tools sit in the same position.

What to change first

Set the browser's preferred language before touching anything else, then reload and see whether the interface follows. If it does and the machine runs macOS 14 or later, install the official app and keep the browser for the second account. If the machine is on macOS 13 or the interface language needs to differ per account, build one named window per profile with Kagemusha and run the typing test before deciding it is the permanent setup.