Compress Video for X (Twitter): Fit the Limits, Free

What X's own pages say (read 15 October 2026)

For a video posted on the web by a free account, X's video help page gives these limits: a length of at most 140 seconds (2 minutes 20 seconds), a file size of at most 512 MB, a picture no larger than 1920 × 1200 pixels (or 1200 × 1900 for a tall video), a frame rate of at most 40 fps, a bitrate of at most 25 Mbps, and a shape between 1:2.39 and 2.39:1, which means width divided by height from 0.42 to 2.39. The tool checks your file against exactly these numbers, and this page reads them from one shared list that is meant to be re-read from X's pages about every 90 days. If a number matters to you, open X's help page and check it, because X changes these pages.

What the tool does to your video

The picture is scaled down to fit the size box for its shape. It is never enlarged, and the sides are made even numbers, which H.264 needs (an odd side loses one pixel). The shape is kept unless black bars are added, as described below. The frame rate is changed only if it is over the limit, and then by a whole number so the motion stays smooth: a 60 fps video becomes 30 fps, not 40 fps. The video bitrate is held to 90% of X's limit (22.5 Mbps at most) with a maximum rate and a buffer size, which leaves room for the sound. The result is always an MP4 with H.264 video in the High profile and AAC-LC sound, with the index at the front of the file. The sound is 128 kbps, or less when the tool is fitting a small size (see below). A video with more than two sound channels is mixed down to stereo, and to mono when the size budget is very tight.

How it keeps the file under the size limit

First the video is encoded for quality (the Balanced choice uses CRF 23) with the bitrate cap above. If that file is over the size the tool aims for, it works out the bitrate that fits from the video's length and encodes again, and if that is still over it tries once more at a lower bitrate: at most two more encodes in all. It aims about 6% under 512 MB. X states the limit as "512MB"; the tool counts that as 536,870,912 bytes, so aiming 6% under also keeps the target below 512,000,000 bytes, but with at most two more tries it aims and does not guarantee. When it fits a size, it may also lower the picture size further (by this site's own rule of thumb for how much picture a bitrate can carry) and use a lower sound bitrate. You can also choose a smaller size of your own: 5, 10, 25, 50, 100 or 250 MB from the list, or type one from 0.1 to 4000 MB, counted in megabytes of 1,000,000 bytes. Then, if your file is bigger than that size, the tool goes straight to the bitrate that fits it, as the compress to a size tool does. A very long video may not fit a small size with a usable picture, and the tool says so instead of making an unwatchable one.

A shape outside the range

X accepts a shape from 1:2.39 to 2.39:1. A video that is wider or taller than that (an ultrawide recording, a very long vertical clip) is outside it. By default the tool adds black bars to the short side until the shape is just inside the range, without stretching or cropping the picture, and the long side is not touched. You can switch that off and leave the shape alone, and the result report will then show the shape rule as not met. If you would rather crop than add bars, use the aspect ratio tool first.

What it does not do

It compresses; it does not shorten. If your video is longer than 140 seconds (2 minutes 20 seconds), you see a warning before anything runs, and the result will be as long as the original, so cut it first with the video trimmer or split it into parts. It does not crop, add captions or change the sound beyond what is described above. It judges the frame rate by the higher of the two figures FFmpeg reports (the average and the nominal rate), so a variable-frame-rate recording is judged by its higher figure. And it cannot promise that X will accept the file: X runs its own checks when you post, and the tool only measures the rules X publishes.

Premium accounts and Media Studio

The tool checks the limits for a free account on the web. X's own pages do not agree about Premium video limits: some give 4 h, 16 GB and others about 3 h, 8 GB, and one page gives Android a shorter limit, so the tool does not use any of them. Media Studio and the normal post box also differ: X's video page says Media Studio allows a higher frame rate, so a file can pass there and fail in the normal post box, and this tool uses the normal post box rule of 40 fps. Photos and GIFs have their own, different limits and are not covered here.

Checking the result

When the tool finishes, it reads the finished file with FFmpeg, on your device, and shows each rule next to the number it measured: length, file size, picture size, shape, frame rate, bitrate and format, each marked as met, not met or could not be measured. It is a measurement of the file you are about to download, not a prediction. To look at every detail of any video yourself, the video metadata viewer shows the full stream information.

Sources and checks

• X Help: videos on X: The page the length, file size, picture size, frame rate, bitrate and shape limits for a free account come from.
• X Help: longer videos with Premium: One of several X pages that give Premium video limits; they disagree with each other, so the tool does not check against them.