Facebook takes the file unchanged, with Reels following separate rules from ordinary posts.
Save a video from X in a form Facebook will accept. Facebook takes the file unchanged, with Reels following separate rules from ordinary posts. The download is a plain MP4 copied straight from X, with no watermark added and nothing re-encoded, which is exactly what Facebook wants as an input. Below: the requirements that actually matter, which resolution to pick, and the mistakes that cause an upload to be rejected or look soft.
Facebook accepts MP4 with H.264 and AAC for feed posts, Stories and Reels. Reels run up to 90 seconds; ordinary feed videos can be far longer.
The download here is an ordinary MP4 with H.264 video and AAC audio, which is the format Facebook is built around. There is no conversion step to get wrong and no container to fix.
Upload at 1080p when it is offered. Facebook compresses heavily on upload and a lower-resolution source shows it, particularly on anything with movement or text on screen.
As a general rule, take the highest resolution the post offers. Facebook will compress whatever you give it, and starting from a better source means the compression has more to work with. Handing it a 480p file to save time produces a visibly worse result than handing it 1080p, because every stage of compression after that is working from less.
Feed videos handle landscape, square and vertical without complaint. Reels are 9:16 and will crop a landscape clip, so crop it yourself first if the framing matters.
This is the single most common reason a re-shared clip looks wrong. Most X videos are landscape or square, because that is how they were filmed, and forcing one into a vertical frame either crops the sides off or leaves bars above and below. Neither is fixed by the download; both are fixed in whatever you crop with before uploading.
X does not brand the video files it serves, and nothing is added here either. What you download is what was published.
If you have seen watermarked downloads before, they came from a tool that added its own branding to advertise itself, not from X. That is worth avoiding for Facebook specifically: a visible third-party watermark reads as reposted content, which is the kind of thing recommendation systems quietly deprioritise.
Upload from Downloads through the Facebook website or app. Saving into Photos or Gallery first makes the file easier to find in the mobile picker.
On a phone, the file lands in your Downloads folder or the Files app, and every app that accepts video can reach it from there. On a computer it goes to Downloads and can be dragged straight in. No import, sync or library step is needed in either case.
Reposting is where copyright actually bites. The person who filmed or posted the video owns it, and saving a copy does not change that, whatever platform it ends up on. Most platforms, Facebook included, will remove reposted content on a rights-holder complaint and may penalise the account that posted it.
Credit is not a licence, but asking is usually enough: many people are happy to have a clip re-shared if they are asked first. Saving a clip for yourself, or re-sharing your own posts across platforms, raises none of this.
Open the post on X, tap or click Share, then Copy link.
Drop the link into the field at the top of this page.
Take the highest resolution offered, then upload it to Facebook as you normally would.