Decide which Gmail account opens first

Typing mail.google.com and landing in the wrong inbox is a small failure that repeats twenty times a day. The obvious assumption is that somewhere in Google settings there is a switch marked default account, and that flipping it will make the work address open first. That switch does not exist. What decides which account opens first is the order the accounts were signed into that browser, and once that is understood the fix becomes mechanical rather than a hunt through preference screens.

This matters more than it first appears, because the same hidden ordering also decides which account is used by every Google service that does not support multiple sign in at all.

The default account is a position, not a preference

When a second Google Account signs into the same browser, Google does not give it a name in the address bar. It gives it a number. The first account signed in is mail.google.com/mail/u/0/, the second is /u/1/, the third is /u/2/. Visiting the bare address mail.google.com sends the browser to position 0.

So the default account is whichever account currently sits at position 0, and position 0 is claimed by the first account to sign in after the browser had no Google session at all. There is nothing to configure. There is no star to click, no radio button in account settings, and no way to promote an account from third place to first while leaving the others alone.

Two consequences follow from this design, and both of them show up in real work.

The number is not stable. Sign out of the account at /u/1 and the account that was at /u/2 slides up to take that slot. Any bookmark, saved link, or memorised address pointing at /u/2 now opens a different mailbox, with no warning and no error.

The number is local. It describes a position in one browser on one machine. A link copied out of the address bar carries /u/1 inside it, and on a colleague's Mac /u/1 is somebody else's account. That mismatch is the usual reason a shared Google Docs or Gmail link produces a permission error for the recipient while opening perfectly for the sender. Stripping the /u/N/ segment out of a link before sending it removes that failure completely.

The reset that actually changes which account opens first

Because position 0 is assigned on first sign in, the only supported way to change the default is to clear the session and rebuild it in the order wanted.

The sequence is short. Open the account switcher in the top right and choose to sign out of all accounts. Google signs out of every account in that browser at once, which is worth knowing in advance: there is no way to drop one account and keep the rest. Then sign in with the account that should be the default. Confirm that mail.google.com now opens that inbox. Only after that, add the remaining accounts in the order that suits the rest of the day.

Three things commonly go wrong during this.

It has to be done per browser profile

The ordering belongs to the browser profile, not to the Google Account. Doing the reset in Chrome does nothing for Safari, nothing for a second Chrome profile, and nothing for the same account on a phone. Anyone who works across two Macs has to repeat it on both.

Two factor prompts arrive all at once

Signing out of everything means signing back into everything. Accounts protected by a security key, an authenticator app, or a passkey will each ask for verification during the rebuild. Doing this ten minutes before a meeting is how people end up locked out of the account they most needed.

Browser sync has its own identity

In Chrome, the account signed into the browser for sync is a separate concept from the accounts signed into Gmail in a tab. Resetting the Gmail ordering does not change which account owns the profile's bookmarks and extensions, and vice versa. Treating them as one setting leads to a lot of confusion later.

Worth checking before signing out of everything

The reset is reversible in principle and unpleasant in practice, because it puts every account through verification at the same moment. Five minutes of preparation removes most of the risk.

Confirm that each account can actually be signed back in. That means knowing where the second factor lives for every one of them: an authenticator app on a phone that is charged and present, a security key that is in the bag rather than in a drawer at home, or a passkey stored in the keychain of the machine being used. Accounts that have not been signed into for months are the ones most likely to demand something unexpected.

Check the recovery details on the account that will become the default. Recovery phone numbers and addresses go stale, and discovering a dead recovery address during a sign in challenge is a bad time to find out.

Note which account currently owns what. Browser sync, saved passwords in the browser's password manager, and any Chrome extensions tied to a specific account all belong to the profile rather than to the Gmail ordering, and their behaviour after the rebuild depends on which account the profile itself is signed into.

Finally, decide the order in advance and write it down. The account signed in first takes position 0, and the rest take positions in the order they are added. Adding accounts in an arbitrary order and then finding the numbers unsatisfactory means doing the whole thing again, because there is no way to reorder without another full sign out.

Where the default account leaks into everything else

If the default only affected which inbox loaded, the ordering would be a minor annoyance. It reaches further than that.

Google products vary in how well they handle multiple sign in. Gmail, Drive, and Calendar cope reasonably. Many other surfaces do not, and when a product does not support multiple sign in it silently uses position 0 rather than the account currently on screen. The page loads, the action completes, and nothing indicates that it ran as a different identity.

The same pull applies to any third party service offering a Sign in with Google button. The flow reaches for the default account first, which is how a personal address ends up owning an account that was meant to belong to the company.

Notifications carry the problem out of the browser entirely. A desktop notification raised by Gmail in a tab identifies the browser, not the account. Three accounts produce one undifferentiated stream of alerts, and clicking one can raise whichever tab happens to be in front. The account ordering is invisible in exactly the moment a decision has to be made about whether to interrupt the current task.

Downloads inherit the same ambiguity. A file saved from a document in one account lands in the same Downloads folder as everything else, with nothing in the file itself recording which identity it came from. For anyone handling client material under a confidentiality agreement, that is a filing problem rather than a convenience problem.

The pattern behind all of these is worth stating plainly: the browser is a single identity as far as macOS is concerned, and the account ordering is a detail hidden inside it. Anything that crosses the boundary out of the browser, whether a notification, a download, a link, or an authentication flow started by another application, arrives with the browser's identity rather than the account's.

Four ways to control which account opens first

The reset is one option among several, and it is the weakest of them because it holds only until the next sign out. The realistic choices look like this.

	Reset the sign in order	Separate browser profile per account	One window per account	Second browser for the second account
Default stays put over time	Only until the next sign out	Yes	Yes	Yes
Accounts signed in at once	All of them	All of them	All of them	All of them
Notification says which account	No	No	Yes	Partly
Separate Dock icon	No	No	Yes	Yes
Extensions and settings	Shared	Separate	Depends on the tool	Separate
Risk of replying from the wrong address	High	Low	Low	Low
Setup effort	Ten minutes, repeated	Ten minutes, once	Ten minutes, once	Fifteen minutes, once
Cost	Free	Free	Free or paid	Free

Resetting the order suits someone with two accounts who rarely signs out. Browser profiles are the standard next step and remove the wrong sender problem entirely, because each profile holds its own cookies and its own position 0. Their limit is presentation: every profile is a window of the same application, so the Dock shows one icon, and the application switcher shows the same name repeated.

Running each account in its own window is the only option in the table that fixes notifications, because the alert then comes from something with its own name and icon. That approach is what a browser that keeps each web app in its own window is built to do, and the way sessions are kept apart is described on Workspaces.

Using a second browser application works and costs nothing, though it means maintaining two sets of extensions, two update cycles, and two sets of saved passwords.

Making the choice hold on macOS

A default that survives contact with the rest of the Mac needs two more things.

The first is link handling. macOS sends every link clicked in Mail, Slack, or Notes to the default browser, and that browser opens it in whichever profile was last in front. A calendar invite for the work account can therefore land in the personal profile even when the ordering inside Gmail is correct. Chrome profiles can be pinned to the Dock individually, which makes it possible to start in the right one, but nothing in macOS routes an incoming link to a particular profile by itself.

The second is the Dock. Since macOS Sonoma, Safari can add any website to the Dock as a web app, which gives one Gmail account a real icon and a real window separate from browsing. Documentation for that behaviour is on Apple's support site.

You can add a website to the Dock, then open and use it like an app. Source: support.apple.com

That covers one account cleanly. The friction appears at the second one, because each web app still shares the underlying Safari session, so two Gmail accounts installed this way land back in the same /u/N ordering. Tools built for this problem keep a separate session per window instead, and the list of services known to work that way is kept on Supported apps. Anyone already comparing options in this category can see how feature coverage and pricing differ on Compared with Wavebox.

What to change first

Start with the cheapest test: sign out of everything once, sign in with the account that should open first, and see whether the default holds for a week of normal work. If it survives, nothing more is needed. If notifications remain ambiguous or the second account keeps capturing links, the problem is not the ordering and no amount of resetting will fix it, so give each account its own window and its own icon. The pricing for that route is on SpaceDeck.