When you enter a verification code and select Don't ask again on this device, we store a cookie in your web browser so that you don't have to enter a code again. This means that a trusted device is specific to the browser. For example, if you select Don't ask again on this device when signing in with Internet Explorer, you're still prompted to enter a verification code in Google Chrome on the same computer.

Incognito window in Google Chrome

The browser window is black or dark grey, rather than light grey:

InPrivate window in Microsoft Edge

The InPrivate label at the top left denotes when you're using an InPrivate window:

Private browsing in Safari on iPhone, iPad or iPod touch

When private browsing is on, the Safari window is dark grey and the Private button is selected.

Blocked cookies in Safari on iPhone, iPad and iPhone touch

If you block cookies in Safari, you're always prompted to enter a verification code each time you sign in, even if you have previously selected Don't ask again on this device. To review your settings:

• In iOS 11, open the Settings app and go to Safari > Privacy & Security. There's an option labelled Block All Cookies.
• In iOS 8, 9 or 10, open the Settings app and go to Safari > Privacy & Security > Block Cookies. Choose from Always Block, Allow from Current Website Only, Allow from Websites I Visit or Always Allow.
• In iOS 7 or earlier, open the Settings app and go to Safari > Privacy & Security > Block Cookies. Choose from Never, From third parties and advertisers or Always.