Open a second Gmail account without signing out

Two Gmail accounts are signed in. The switcher in the top right shows both, so the problem looks solved. Then a reply goes out from the personal address instead of the work one, a link shared with a colleague opens an access error on their machine, and a notification arrives with no clue which of the two inboxes it belongs to. Nothing broke. This is what multiple sign in does when it is asked to act as account separation.

The useful question is not how to add another account, which takes ten seconds, but which parts of the browser stay shared afterwards. That determines whether a second tab is enough or whether the account needs a container of its own.

What the browser is doing when two accounts are signed in

Signing into a second Google Account in the same browser does not create a second session in any meaningful sense. It adds the account to a list, and Google numbers the list. The first account signed in becomes mail.google.com/mail/u/0/, the second becomes /u/1/, the third /u/2/.

That number is a position, not a name. Three consequences follow from that one fact, and most of the complaints about running several accounts in one browser trace back to them.

The number moves. Sign out of the account at /u/1 and whatever sat at /u/2 slides down into its place. Bookmarks, saved links, and habits that pointed at /u/2 now open a different mailbox, silently.

The number is local. A link copied out of the address bar carries /u/1 inside it, and on another Mac /u/1 is a completely different account. This is the whole explanation for the familiar situation where a Google Docs or Gmail link works perfectly for the sender and returns a permission error for the recipient. Deleting the /u/N/ segment from a link before sharing it removes that failure entirely.

Sign out is not per account. Signing out from the switcher signs out of every Google account in that browser at once. Keeping one account live while dropping another is not an option the design offers.

Four ways to open another account in the same browser

There are four arrangements in common use on a Mac. They differ in how much of the session is shared, which is the only property that matters here.

The account switcher

Click the avatar, pick the other account, and it opens in a tab. Cookies, extensions, history, and saved passwords are shared, because it is the same browser session with two identities stacked inside it. Setup cost is zero and it holds up for two accounts that are rarely used at the same time.

A private or incognito window

A second account can be signed into a private window while the first stays signed in normally. The catch on Chrome is that every incognito window shares one incognito session, so a third account cannot be added the same way, and everything is discarded when the last incognito window closes. Useful for a one off check, not for daily work.

A second browser profile

Chrome, Edge, and Firefox all support profiles, and Safari added them in macOS Sonoma. A profile has its own cookies, extensions, history, and bookmarks, which is genuine separation rather than stacking. Two profiles can each hold a different Gmail account at /u/0 and never interfere. The limitation is at the operating system level. Every profile is another window of the same application, so all of them share one Dock icon and appear under one name in the application switcher.

A container tab

Firefox with the Multi-Account Containers extension from Mozilla assigns tabs to colour coded containers with separate cookie jars. Two Gmail accounts can sit in two containers inside one window. This is the lightest form of real isolation, and it stays inside the browser, which means the notification and Dock behaviour is unchanged.

	Account switcher	Private window	Second profile	Container tab
Cookies separated	No	Yes	Yes	Yes
Survives a restart	Yes	No	Yes	Yes
Extensions separated	No	Mostly disabled	Yes	No
Third account possible	Yes	No	Yes	Yes
Own Dock icon	No	No	No	No
Setup time	None	None	A few minutes	A few minutes

Where a shared session leaks

The account switcher works well inside Gmail, Drive, and Calendar. The failures happen at the edges, and they are quiet rather than loud.

Some Google surfaces do not implement multiple sign in and simply act on the account at position zero. A link is clicked, the page loads, and the action completes under an identity nobody chose. Third party sites that offer sign in with Google behave the same way, because the sign in flow reaches for the default account rather than the one currently on screen. Signing up for a service with the wrong account is easy to do and awkward to undo, since the subscription and the billing address end up attached to it.

Extensions are shared too. An extension installed for personal browsing runs with the same permissions on the work mailbox, which is a policy problem in some organisations regardless of how careful the person is.

Downloads land in one folder with no record of which account they came from. Attachments from two clients end up side by side, distinguished only by filename.

Notifications carry the browser's name, not the account's

This is the limit that no amount of tab discipline gets past, and it is worth understanding precisely.

Web notification permission is granted per origin. Both accounts live at mail.google.com, so there is one permission covering both. The choice is all notifications or none. There is no arrangement inside the browser where the work account can interrupt and the personal account cannot.

The notification itself is issued by the browser, so it carries the browser's name and icon at the system level. A macOS notification saying a new message arrived does not say which inbox received it, and Focus filters, which work by application, cannot tell the two apart. Clicking the notification usually brings forward the tab that was already open, which may not be the account that received anything.

A browser profile does not fix this either, because a profile is still the same application to macOS. Only a container that presents itself to the system as its own application gets its own name in Notification Centre and its own line in a Focus filter. That is the practical dividing line between arrangements that separate the session and arrangements that separate the account. A browser built so each web app runs in its own window is one way to reach that line, and it is worth being clear that this is the specific thing being bought, not extra tab management.

Keeping the accounts apart once they are separated

Separation only helps if the two containers are distinguishable at a glance. This is where most profile setups quietly fail, because two Chrome windows look identical until the wrong one has already been used.

Chrome and Edge attach a name, an avatar, and a theme colour to each profile, and the colour is the part that works. A blue window and an orange window are separable from across the room, while two windows labelled Profile 1 and Profile 2 are not. Setting the colour takes a few seconds and prevents most of the mistakes that separation was supposed to solve. Firefox containers use the same idea with a coloured underline on the tab.

Getting into the right profile directly is the other half. Clicking the browser icon in the Dock opens whichever profile was last used, which means the first action of the day is often a switch. On macOS, a specific Chrome profile can be launched from the command line by passing --profile-directory with the profile's folder name, and that command can be wrapped in a small launcher so the profile has something clickable. Chrome on macOS does not create a separate Dock icon per profile the way it does on Windows, so anything of that kind has to be built rather than switched on.

The deeper limit is the same one that shows up with notifications. All these arrangements produce more windows of one application. macOS keeps its counters, its Focus rules, and its application switcher entries at the application level, so a per profile badge or a per profile Focus rule is not something that can be configured. Only a container that registers itself as a separate application gets those, which is the distinction worth checking before assuming a profile will solve a notification problem.

Working out which accounts actually need a container

Not every address deserves its own window. Two questions sort the list quickly.

Does mail need to go out under that identity? A client address that must show the right name in the recipient's inbox is different from an address that only ever receives receipts.

Does mail need to be noticed within the hour? A shared support address usually does. A newsletter address does not.

Accounts that answer no to both belong in one inbox rather than a container. Gmail can fetch from other addresses by POP, with a documented limit of five, and Send mail as allows replies to leave from a verified address. Everything about that arrangement is slower and less precise than a dedicated window, and for a low traffic address none of it matters.

Accounts that answer yes to both are the ones worth separating properly. In most working setups there are two of them, occasionally three. Anyone deciding between the established tools in this category will find the differences in supported services and pricing laid out in Compared with Wavebox, and the list of services already set up to run in a dedicated window is on Supported apps.

There is also a case where the second account should not be opened in the browser at all. An address that exists only to receive automated mail, such as invoices from a hosting provider or alerts from a monitoring service, does not need a session. Forwarding it into the main account with a filter that labels it on arrival gives the same visibility with none of the switching. The account remains available for the rare occasion it is needed, and it stops occupying attention the rest of the time.

Google Workspace accounts have a fourth option that is often forgotten. Delegation lets one account open another mailbox without signing into it, which suits a shared address that several people handle. Delegates can read, send, and archive, but not change settings, so it fits a support inbox better than a second personal account.

What to change first

Strip the /u/N/ segment out of Gmail and Drive links before sending them, because that costs nothing and removes the most frequent daily annoyance. Then list the accounts and mark the ones that must both send under their own name and be noticed quickly. If two of them qualify, the next step is a container that macOS recognises as its own application, which is what a SpaceDeck style window per account provides and what a second tab, by design, cannot.