1:1, 4:5, 9:16, 16:9: the image aspect ratio guide that's actually used

"Aspect ratio" and "resolution" are not the same, even though they're constantly confused. Resolution is how many pixels a file has; aspect ratio is the shape of that rectangle — wider than tall, taller than wide, or exactly square. The same photo can be exported at different resolutions while maintaining the same aspect ratio, but changing the aspect ratio almost always means cropping something.

1:1 — the square, the most neutral of all

Neither horizontal nor vertical: the square takes up the same space no matter the viewing direction, making it safe for catalogues, carousels and any content that may end up reused in several different places. It's also the "safe but bland" ratio — it communicates little urgency, because it doesn't claim more vertical space in a feed than it's allotted.

4:5 — the vertical that gains space without going to extremes

Slightly taller than wide, the 4:5 is the midpoint between the square and the full vertical: it occupies more screen surface in a mobile feed than the 1:1 without reaching story length. It's the ratio that the networks themselves most often recommend for standard posts, precisely because it maximises space without sacrificing scene context.

9:16 — full vertical, designed for full screen

The story, reel and short format: it occupies the full available height of the phone held naturally. It leaves no space for anything else on screen, which also means it demands more compositional discipline — a single protagonist, no competing secondary elements, because there's no "rest of page" around for the eye to rest on.

16:9 — the widescreen, designed for screens not fingers

The proportion of cinema and modern television, inherited directly by YouTube thumbnails and many desktop banners. It works well for those who view it on a wide screen — monitor, TV, laptop — and worse on a phone held vertically, where it leaves black bars at the top and bottom unless adapted. That's why it coexists with 9:16 on the same platform (YouTube uses both depending on whether it's a regular video or a Short), rather than replacing it.

Quick reference table

• 1:1 (square): catalogues, carousels, reusable content across networks.
• 4:5 (soft vertical): standard feed posts — the most recommended by default.
• 9:16 (full vertical): stories, reels, shorts — full screen on mobile.
• 16:9 (widescreen): YouTube thumbnails, banners, and desktop-first content.