How to Compress a Video for Sharing Without Ruining It

Phone and screen recordings are big. A couple of minutes of modern phone video can run to hundreds of megabytes, while email attachments are usually capped around 20 to 25 MB and many upload forms allow even less. Compressing the video is the answer, but the settings are rarely explained. This guide shows what actually decides a video's size, what the resolution and quality choices do and how to meet a limit with as little visible damage as possible.

What makes a video file big

File size is roughly bitrate multiplied by duration. Bitrate is how many megabits the encoder spends on each second of video. A two-minute clip (120 seconds) at 8 megabits per second is 960 megabits, which is 120 megabytes after dividing by 8. The same clip at 2 megabits per second is 30 megabytes.

Bitrate is driven by the number of pixels in each frame, how much changes from frame to frame and the quality the encoder is asked to keep. Pixels are the easiest lever to pull.

• 1080p is 1920 by 1080, about 2.07 million pixels per frame.
• 720p is 1280 by 720, about 0.92 million, or 44 percent of 1080p.
• 480p is about 854 by 480, roughly 20 percent of 1080p.
• 360p is 640 by 360, roughly 11 percent of 1080p.

Dropping from 1080p to 720p therefore removes more than half the pixels the encoder has to describe. Audio matters far less: a stereo track at 96 to 128 kbps is tiny next to the picture.

What the Video Compressor settings do

The Video Compressor has two choices.

Maximum height can be the original size, 1080p, 720p, 480p or 360p. The video is scaled down to that height with its proportions kept, and a video that is already smaller is left alone instead of being enlarged.

Quality has three levels: High, Balanced and Smallest. They set the x264 constant rate factor (CRF) to 23, 28 and 33, and the audio bitrate to 128, 96 and 64 kbps. CRF is a constant-quality setting. Instead of forcing a bitrate, the encoder spends more bits on complex scenes and fewer on simple ones. Lower numbers mean higher quality and bigger files, and as a rule of thumb every increase of 6 roughly halves the bitrate. It also means you cannot type a target size in megabytes: the result depends on the footage, so a mostly static screen recording shrinks far more than a football match.

The output is always H.264 video with AAC audio in an MP4 file, arranged so playback can start before the whole file has downloaded. That combination plays in current browsers and on phones. One trade-off: the tool uses a fast encoding preset so it finishes in a reasonable time inside a browser, so a slower desktop encoder can make a slightly smaller file at the same quality.

Choose settings for where the video is going

• Email or chat attachments: 720p with Balanced, or 480p with Smallest if the limit is tight.
• Web pages and social posts: 720p or 1080p with Balanced.
• Screen recordings with small text: 1080p or the original height with Balanced, because fine text is the first thing to blur.
• Archive copies: the original height with High, or no compression at all.

Think about the screen where it will be watched. On a phone held at arm's length, the gap between 720p and 1080p is small, while the file size gap is large.

A workflow that saves the most space

1. Cut first. Every second you remove is size you never pay for. The Video Trimmer cuts to exact start and end times. Precise mode re-encodes for exact cuts, while Fast mode copies without re-encoding, which is lossless but starts at the nearest earlier keyframe. If a limit applies per file, the Video Splitter breaks a recording into equal parts, up to 24.
2. Fix orientation early. If the footage is sideways, the Video Rotator turns it by 90 or 180 degrees. It re-encodes, so do it before compressing and the video is re-encoded as few times as possible.
3. Drop the sound if it is not needed. The Video Muter removes the audio track and copies the picture untouched.
4. Compress last, from the original. Open the Video Compressor and choose the file. The tool reads its size, length and frame rate, then you pick a height and quality and click Compress video. The result shows its size and how much smaller it is than the original.
5. Watch the result at the size it will be viewed, including text, fast motion and dark scenes. If it is still too big, run the original again with a lower height or quality.

Limits to know about

The tools process the file in your browser with ffmpeg.wasm, a WebAssembly build of ffmpeg, so the video is never uploaded. The price is speed and memory. The first use downloads about 10 MB of engine files, long or high-resolution videos take longer than they would in desktop software, files over 500 MB are refused and anything over 150 MB gets a warning. For a very long 4K recording, a desktop encoder is the better choice.

Related jobs

If you only need the sound, MP4 to MP3 extracts it at 128 to 320 kbps. For a short looping clip instead of a video, try Video to GIF. The Screen Recorder saves WebM files, which the compressor can turn into an MP4, and the Video Speed Changer can shorten a long recording by playing it up to 4 times faster.