Gmail has a hidden preview panel that gives you a dual-pane view of your emails---just like in Outlook and other desktop email clients. Here's how to enable it on the web and choose a horizontal or vertical split.

First, head to your Gmail inbox. Click the Settings cog and then click "Settings."

The Settings option in Gmail

Choose the "Advanced" tab.

The Advanced Settings tab

The Preview Pane option is towards the bottom. Choose "Enable" and then click "Save Changes."

Preview Pane radio buttons

You'll be taken back to the Inbox, where a new "Toggle split pane mode" button will be visible next to the Settings cog.

The "Toggle split pane mode" button

This is a mouthful, so we're going to refer to it as the "Toggle preview" button.

If you click the arrow next to the Toggle preview button, you can choose whether the preview pane is split vertically, or horizontally.

The preview pane options

The "Vertical split" mode means the preview pane opens on the right-hand side of the screen, with your emails on the left.

The preview pane to the right of the inbox

This is more useful if you've got a wide-screen monitor. The "horizontal split" mode means the preview pane opens at the bottom of your inbox, with the emails on top.

The Preview Pane below the inbox

This is more useful if you've got a square monitor, or you use a wide-screen monitor rotated 90°. But whichever way you prefer to have the preview pane, you can move the edge left or right, or up and down, to size it as you want. Changing between vertical and horizontal will deselect any mail that's currently being shown in the preview pane, so you'll have to select the email again to preview it.

Once you've chosen your preferred split mode (vertical or horizontal), you can click the Toggle preview button to switch between showing and hiding the preview pane by clicking "No split" on the Toggle preview menu. This won't remove the Toggle preview button; it will just swap between showing and hiding the preview pane. If you want to remove the Toggle preview option altogether, you'll need to go back to Settings > Advanced and disable the preview pane there.

When you've got the preview pane enabled, an additional option becomes available. Head to the Settings cog, click "Settings," and in the General tab that opens there will be a new Preview Pane option about 2/3 of the way down.

The Preview Pane option

This option lets you choose when a mail is marked as read if you're viewing it in the preview pane. The options are:

  • Immediately
  • After 1 second
  • After 3 seconds (this is the default)
  • After 20 seconds
  • Never

Choose whichever option you want, scroll down to the bottom of the page and click "Save Changes" to return to the Inbox. This setting only has an effect when you have the preview pane enabled and have chosen either Vertical or Horizontal split. If you disable the preview pane functionality, this option will disappear.

Now you can preview your emails as if you're using a desktop email client. Sadly this option isn't available in the Gmail mobile app yet---which would be useful for tablets---but you can view Gmail through a browser on your mobile device if this Preview Pane is a game-changer for you.