Aspect Ratios & Resolution: A Platform Playbook
Instagram wants 4:5, YouTube wants 16:9, stories want 9:16. Learn to generate for the frame — not crop into it.
Cropping a square image into a story format is how good images die: heads get cut, subjects drift off-center, negative space lands in all the wrong places. The fix costs nothing — pick the aspect ratio before you generate. The model composes *for the frame*: give it 16:9 and it builds wide establishing shots, give it 9:16 and it stacks a vertical visual hierarchy. Same prompt, different frame, completely different composition.
The Platform Cheat Sheet
| Platform | Ratio | Pixels |
|---|---|---|
| Instagram feed (portrait) | 4:5 | 1080 × 1350 |
| Stories / Reels / TikTok | 9:16 | 1080 × 1920 |
| YouTube thumbnail | 16:9 | 1280 × 720 |
| X / Twitter post | 16:9 | 1600 × 900 |
| LinkedIn link image | 1.91:1 | 1200 × 627 |
| Square (feed, profile grids) | 1:1 | 1080 × 1080 |
Two ratios earn special attention. 4:5 is the Instagram feed power move — it occupies about 25% more screen than a square post, which is free real estate in the scroll war. 16:9 thumbnails live or die at tiny sizes: on a phone, your YouTube thumbnail renders about 168 pixels wide, so it needs one oversized subject, screaming contrast, and three words of text maximum.
Resolution Strategy: Generate Native, Upscale to Deliver
Models have a native sweet spot — typically around 1024px on the long edge — where composition and coherence are best. Fighting that is pointless. The pro pattern: generate at native resolution in your target ratio, then upscale the final pick to delivery size. Screens are forgiving (72-96 PPI), but print is not: quality print wants 300 DPI, which means an A4 poster needs roughly 2480 × 3508 pixels — a 2x-4x upscale from any native generation.
YouTube thumbnail, built for 168px
YouTube thumbnail, 16:9: extreme close-up of a shocked man holding a tiny glowing robot in his palm, face filling the right third of the frame, electric blue rim lighting, saturated orange background, bold high contrast, large empty area on the left for title text
Everything here is a small-size decision: one subject, face scale, contrast, and reserved space for text you will add later. Composition for the destination, not for your monitor.
Need the Same Image in Two Ratios?
Do not crop — extend. Outpainting generates new canvas beyond the original borders, so a 4:5 feed hero becomes a 16:9 banner by growing the scene sideways instead of amputating it. And when a client asks for "the same visual for feed, story, and thumbnail", generate once per ratio with the same prompt and reference — the consistency techniques from the previous lesson keep them looking like one family.
Generate the same concept in 4:5, 9:16 and 16:9 and watch the model recompose for each frame. Open Create Image