1:1 · 4:5 · 9:16
Resize a video for Instagram Reels and feed
Instagram crops anything that does not match its expected shapes, usually cutting off the part you cared about. Pick the target format and keep the whole frame.
Processed on your own hardware · never transmitted, never stored
What happens when you drop a file in
The file stays put. Your browser opens it the same way an image viewer would. There is no transfer, which is why there is no upload bar to watch.
An encoder arrives once. The first job on this site pulls down a compiled build of FFmpeg, roughly 30 MB. It is kept afterwards, so every job after the first starts immediately.
Your own hardware does the job. The work happens in this tab, on your processor. A laptop from the last few years handles short clips in well under real time.
The result lands in Downloads. Assembled in memory and handed straight to your browser. Close the tab and every trace of it is gone.
Which format for which placement
Portrait at 4:5 takes up the most screen space in the feed without being cropped, which is why most creators default to it. It is the safest choice for a normal post.
Square at 1:1 is the classic format and still displays cleanly everywhere, though it occupies less of the screen than portrait.
Vertical at 9:16 is what Reels and Stories expect. Anything narrower gets letterboxed by Instagram itself, usually with results nobody chose.
Padded, not cropped
This tool fits your whole video inside the target shape and fills the remainder with black, rather than cutting the edges off. Nothing you filmed disappears. If you would rather crop tightly to fill the frame, that is a compositional decision better made in an editor where you can see what is being lost.
For a target shape that is not one of these three, work out the numbers with the aspect ratio calculator.
Common questions
Why are there black bars?
Because the entire frame is preserved. Cropping would remove part of your footage without asking.
Which format gets the most reach?
Reels at 9:16 currently get the widest distribution, but that reflects Instagram's priorities rather than anything about the file.
Does it change the length?
No. Only the dimensions change.
Do my files get uploaded?
No, everything runs in your browser.