A portrait Google Slides presentation uses a canvas taller than it is wide. This can suit a poster, a phone-oriented visual, or a vertical display. Google Slides handles this through custom page dimensions rather than a word processor’s page-orientation control.
Set a taller custom canvas
On a computer, open File > Page setup and choose Custom. Enter a width smaller than the height, using the same measurement unit for both values. For example, choose dimensions based on the actual poster or display requirement rather than guessing from the editor window.
Check which field is width and which is height before confirming with OK. Reversed values produce a landscape canvas even when the numbers themselves are correct.
Rework the slide composition
Inspect every existing slide after changing a landscape deck. A wide chart, a two-column comparison, or a background photograph may need a different arrangement. Avoid merely reducing every font until the former layout fits; that often produces a tall slide with unreadable text.
The custom size applies to the presentation. If you need both landscape and portrait deliverables, plan separate files or exports and verify each one.
Test the intended destination
Preview the portrait presentation in slideshow mode and inspect its output format. Check titles, lower captions, and edge spacing at the size the audience will actually see. A landscape monitor may show space beside a portrait slide; that is not proof that the custom dimensions failed. Verify the display or print configuration before making additional changes to the canvas.
References
Reviewed against the linked official product guidance on November 3, 2026. Features, limits, screen labels, and access can vary by account, platform, region, and organization policy.