zerouploads

Video Compressor

Make a video smaller by asking for a quality, not a file size. Nothing is uploaded and there is no watermark.

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  • Private
  • Works offline

Make a video file smaller

Quality

H.264 in an MP4 plays on everything. VP9 in a WebM is smaller at the same quality and takes longer to make.

How long the encoder works on each frame. Slower reaches the same quality in fewer bytes. VP9 only changes on Slow.

How the file is written
Commandffmpeg -i input.mp4 -c:v libx264 -crf 23 -preset medium -vf scale=-2:720 -pix_fmt yuv420p -c:a aac -b:a 128k -movflags +faststart video-compressed.mp4
Choose a video to start

How it works

  1. 01

    Add a video

    Drop it or choose it. It plays here first, so you can see what you are working on.

  2. 02

    Pick a quality

    Good suits almost everything. Drop the resolution too if it is going to a phone.

  3. 03

    Save it

    The bar fills and the file downloads. The page shows what it saved.

How a video gets smaller

Two things decide the size. One is how many pixels each frame holds, which is the resolution. The other is how many bits describe them, which is the quality. Lower either one and the file shrinks.

This tool asks for a level of quality and spends whatever bits it takes to reach it. A still talking head needs very few and comes out tiny. A snowstorm needs many and comes out large. A fixed bitrate would hit a size instead, and let the picture fall apart on the clip that needed more.

That is why the page promises no size before you start. The size depends on what moves in your footage, and you see the real number as soon as it finishes.

Input
MP4, MOV, MKV, WebM and AVI. One video at a time.
Output
H.264 in an MP4, or VP9 in a WebM. Four quality levels.
Resolution
Keep the original, or drop to 1080p, 720p, 480p or 360p.
Sound
Re-encode it at 128 kbps, leave it untouched, or remove it.

What to pick, and when

Phone video is usually 1080p or 4K, and a chat window or an email shows it far smaller. 720p is plenty for chat, email and a slide. Keep 1080p if it is going on a television or into an edit.

Good is the default, and it is CRF 23. High is for footage you will edit again. Smaller suits email limits. Smallest softens the picture in a way you will see on detail like grass or hair.

H.264 in an MP4 plays on everything, which is what you want if you are sending it to someone. VP9 in a WebM is smaller at the same quality and takes longer to make, so it suits a file for your own site.

With H.264, Effort changes how long the encode takes, not the quality you asked for. Slow spends longer on each frame, so the same picture fits in fewer bytes. With VP9, only Slow changes anything, and Fast and Medium run the same.

Frequently asked questions

Is my video uploaded?
No. Your own browser reads and re-encodes it in this tab. Nothing is sent, so there is no upload wait.
How much smaller will it be?
It depends on what moves in the footage, so the page does not guess. The real figure appears when it finishes.
Will it look worse?
A little. Good is hard to tell apart on a phone or laptop screen. High keeps more for editing. Smallest is the one you will notice, on detail like grass or hair.
Should I pick MP4 or WebM?
MP4 if you are sending it to someone, because H.264 plays everywhere. WebM if it is for your own website and you can wait longer for a smaller file.
Why is it slow?
Re-encoding video takes a lot of processing, and your own machine does all of it. A shorter clip, a lower resolution or Fast effort all help.
Can I compress several at once?
No. It works on one video at a time, because the whole file is held in memory while it is encoded.

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