Reels and Stories want a vertical MP4, so the download is the easy half and the crop is the rest.
Save a video from X in a form Instagram will accept. Reels and Stories want a vertical MP4, so the download is the easy half and the crop is the rest. The download is a plain MP4 copied straight from X, with no watermark added and nothing re-encoded, which is exactly what Instagram 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.
Instagram accepts MP4 with H.264 video and AAC audio, which is exactly what X serves. Reels run up to 90 seconds in the app and up to 15 minutes when uploaded from a computer. Stories cut into 60-second segments automatically.
The download here is an ordinary MP4 with H.264 video and AAC audio, which is the format Instagram is built around. There is no conversion step to get wrong and no container to fix.
Upload the highest resolution the post offers, normally 1080p. Instagram re-compresses everything on upload, and it compresses a 1080p source far more gracefully than a 720p one.
As a general rule, take the highest resolution the post offers. Instagram 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.
Reels and Stories are 9:16 vertical. Most X videos are 16:9 landscape, so they arrive either cropped at the sides or letterboxed with bars. Crop deliberately in the Instagram editor or in any phone editor before uploading, rather than letting the app decide for you.
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 Instagram specifically: a visible third-party watermark reads as reposted content, which is the kind of thing recommendation systems quietly deprioritise.
On a phone, save the download into Photos and Instagram will find it in the gallery picker. On iPhone that means opening Files, holding the downloaded video and choosing Save to Photos first.
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, Instagram 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 Instagram as you normally would.