Video Compressor

How to use 4 steps

Choose your video under Video file. MP4, WebM and MOV all work.
Set Resolution and Quality. Balanced suits most videos.
Under Audio, keep or remove the sound, then press Compress Video.
Keep this tab in front until it finishes, check Preview, then press the download button.

Video file

MP4, WebM and MOV. Nothing is uploaded — the file is decoded and re-encoded by your own device.

Compressed Video

How this tool works

The video is decoded and encoded again at a lower bitrate, using the same hardware video encoder your device uses to record. Nothing is uploaded — the file never leaves the machine, which is the main reason to use this rather than a service that wants the upload before it will do anything. You choose a resolution and a quality, and the estimated result is shown before anything starts.

The bitrate is worked out from the pixel count rather than fixed, because a figure that suits 1080p starves 4K and wastes bytes on 480p. A smaller resolution is never upscaled: choosing 1080p for a 720p video leaves it at 720p rather than inventing detail. Audio is re-encoded as AAC into an MP4 where the browser can write AAC; where it cannot, the result is written as WebM with Opus audio instead, which keeps the sound rather than dropping it. Only where neither is possible does the export end up silent.

What compression can and cannot do

Resolution saves more than quality does: halving the dimensions removes three quarters of the pixels, which is a far larger saving than any quality setting. If the video is destined for a phone screen, 720p usually looks identical and is a fraction of the size.
An already-compressed video may come out larger: a file that was encoded efficiently has little left to remove, and re-encoding it spends bits preserving the artefacts of the first pass. The estimate says so before you start, and the result says so afterwards — keep the original in that case.
A WebM result is not a downgrade: AAC, which MP4 requires, is unavailable in Firefox on every platform and in every browser on desktop Linux. On those systems this tool writes WebM with Opus audio instead, so the sound survives — WebM plays natively in every current browser and in most players and editors, just not in some older software that only expects MP4.
MP4 sources encode considerably faster: an MP4 is read frame by frame straight out of the container and handed to the decoder. Anything else — WebM, or a file the demuxer cannot parse — falls back to stepping the video through frame by frame instead, which works with any file the browser can play but is much slower. Converting an awkward source to MP4 first is often quicker overall than compressing it directly.
Keep the tab in front: browsers throttle background tabs heavily, and encoding slows to a crawl or stalls entirely. This matters most on the slower fallback path, but it is worth doing either way.

How the size estimate is actually calculated

The bitrate the [msm_tool slug="video-compressor"] targets is worked out from the pixel count of the chosen resolution rather than fixed at one number, because a bitrate that suits 1080p would starve a 4K export and waste bytes on a 480p one. Encoding runs through the same hardware video encoder the device already uses to record, and the whole job happens without the file ever leaving the machine.

Resolution is the bigger lever, not quality

Halving both dimensions of a frame removes three quarters of its pixels, a far larger saving than moving the quality setting alone can produce. A recording destined for a phone screen usually looks identical at 720p and is a fraction of the size of the same file left at its original resolution — the quality slider is worth adjusting after the resolution, not instead of it.

It never upscales

Choosing a target resolution larger than the source does not invent missing detail; the output is simply left at whatever resolution the source actually was. The setting is a ceiling, not a promise.

An already-compressed file can come out bigger

A video that was efficiently encoded the first time has little redundancy left to strip out, and re-encoding it spends bits reproducing the artefacts already baked into that first pass rather than removing anything meaningful. Where that is likely, the estimate says so before the run starts, and the result confirms it afterwards — the original is usually the better file to keep in that case.

Which setting is actually worth choosing

For sharing or posting to the web, 1080p at a balanced quality covers almost everything without a visible trade-off. For a phone screen or a messaging app, 720p is usually indistinguishable from the original and considerably smaller again — most video is never watched at a size where the difference would register. The smallest-file setting is worth reaching for only when a hard size limit forces it, since it is the point where the saving starts to cost visible quality.

Where sound needs a different container

Audio is re-encoded as AAC into the MP4 wherever the browser can write AAC. Firefox cannot, on any platform, and no browser can on desktop Linux — a limitation of those browsers, not of this tool. Rather than deliver a silent MP4 on those systems, the export switches to WebM with Opus audio instead, which keeps the sound. WebM plays natively in every current browser and in most media players and editors; the only real cost is a file that says .webm rather than .mp4, which some older software that only expects MP4 will not open. The page says which format was used before you download.

Why MP4 sources finish sooner

An MP4 is read directly: the frames are pulled out of the container and handed to the decoder in sequence, so no individual frame costs anything beyond decoding it. Anything the demuxer cannot read — a WebM source, or an unusual MP4 variant — falls back to stepping the video element to each frame in turn and capturing it, which works with any file the browser can play but pays a seek for every single frame. If a source is slow to process, converting it to MP4 first and then compressing is often quicker than compressing it directly.

Keep the tab in front

Browsers throttle background tabs heavily, and an encode running behind another window slows down or stalls outright. This matters most on the slower fallback path, where each frame is already waiting on the video element, but it is worth doing whichever path a file takes.

Frequently Asked Questions

Specific to the Video Compressor. Broader questions about this category are answered on the category page.

How much smaller will my video be?

It depends entirely on the original. Footage straight from a phone or a camera often halves or better. A file already compressed for the web may barely shrink, and the estimate shown before you start is calculated from your actual settings rather than a general claim.

Why is my compressed file larger than the original?

Because the original was already well compressed. Re-encoding then spends bits faithfully preserving the artefacts of the first pass, which is expensive. Choose a smaller resolution or a lower quality, or keep the original.

Is my video uploaded?

No. Decoding and encoding both use your own device, through the same hardware encoder your phone uses to record. Nothing is sent to this site or anywhere else.

Why did I get a WebM file instead of MP4?

Your browser cannot write AAC audio, which MP4 requires — true of Firefox on every platform and of every browser on desktop Linux. Rather than deliver an MP4 with no sound, this tool writes WebM with Opus audio instead, so the sound is kept. Choose "Remove the sound" if you specifically need an MP4 file and audio is not required.

Which setting should I choose?

For sharing or the web, 1080p at balanced quality suits almost everything. For a phone or a messaging app, 720p is usually indistinguishable and much smaller. Reach for the smallest-file setting only when a hard size limit forces it.