What size does this X post preset use?
This page uses a 1600 × 900 preset for a broad landscape post format.
Can I avoid cropping the image?
Yes. Fit keeps the full image visible, and fill keeps it visible while adding a solid background where needed.
Is the resizing done locally?
Yes. The page runs the framing and export client-side in the browser.
What image size should I use for a post on X?
A 16:9 image is the safest choice for a single attachment, and 1600 x 900 is a comfortable size at that ratio. It is also large enough to double as a summary_large_image card.
What is the file size limit for images on X?
5 MB for JPG and PNG uploaded from the web client. A JPG export at 1600 x 900 lands far below it, so the limit mostly matters if you insist on PNG for a photo.
Why is my image cropped in the timeline?
Because the aspect ratio did not match. X fits single images into a roughly 16:9 preview and crops the rest. Exporting at 1600 x 900 means the crop is a no-op.
Does this work for the link preview card as well?
Yes. The summary_large_image card wants a 2:1 to 16:9-ish image, at least 300 x 157 and under 5 MB. A 1600 x 900 file satisfies that, though the card crops closer to 2:1, so keep the subject away from the top and bottom edges.
Should I use fit instead of crop for a screenshot?
Yes, usually. A screenshot rarely has spare edges to sacrifice, so fit or fill keeps the whole capture visible and puts the padding in a flat colour instead of chopping a UI element in half.