The classic link-preview rectangle
A wide card for a shared link
1200 by 628 is the classic pair people prepare for an Open Graph style link preview: a blog share, a Slack unfurl, a post that becomes a card. The shape is wide, close to 1.91:1. A square 1080 photo dropped into that card loses the sides or gains bars. This page is for the card. Compose the headline and the face inside the frame, a little in from the edges, because some clients shave a few pixels when they draw the preview.
Close to other wide presets, and still its own pair
The social resizer’s Facebook post preset is 1200 by 630. Its LinkedIn post preset is 1200 by 627, and that LinkedIn number is a single post, not a carousel. X’s post preset is 1200 by 675. This page is 1200 by 628, the pair you type when a guide or a CMS field names those exact integers. Two pixels matter when a validator checks the file. Do not assume a Facebook post export will satisfy a field that asked for 628.
Type both numbers on one image
Enter 1200 as the width and 628 as the height. The resizer loads the first file only. JPG, PNG, WebP, and GIF can be that file. The ceiling is 10000 pixels on a side, so this card is a shrink for almost any camera original. If you start from a narrow screenshot, enlarging it to 1200 wide will look soft. Upscaling does not invent detail. Use a master that is already at least this wide when the card will be seen on a desktop.
Weight comes after the card is the right shape
JPEG and WebP honor a kilobyte target. Leave the box blank and they save at quality 0.92. PNG ignores that target, which suits a flat diagram and suits a photo less well. Link previews are usually photographs or simple graphics, so JPEG at 0.92 is a sensible default. If the CMS also caps kilobytes, set the target on a JPEG export or pass the file through the image compressor. Keep this classic geometry either way.