Is my video uploaded when I compress it?

No. The Video Compressor runs entirely in your browser. Your video is read from your device, processed locally, and never uploaded to ArrayKit or any server.

Is there a file-size limit for compressing video?

The tool imposes no file-size limit, so you can load clips of any length. The practical ceiling is your device's memory — very large videos use a lot of RAM and CPU because everything runs locally in one browser tab.

Which format makes a video smaller, MP4 or WebM?

WebM usually produces smaller files than MP4 at the same quality, but it encodes noticeably slower in the browser. MP4 is faster and plays almost everywhere, so it is the best default.

What does the CRF quality slider do?

CRF (Constant Rate Factor) controls the quality-to-size trade-off. A lower CRF keeps more quality and produces a bigger file; a higher CRF compresses harder for a smaller file. Around 28 is a good balance for MP4.

Why does compressing a large video take so long?

Compression happens on your own device in a single browser tab, so it cannot tap all your CPU cores the way installed software would. Downscaling the resolution, capping the frame rate, or choosing MP4 speeds things up.

Can I see how hard my computer is working?

Yes. While compressing, a live monitor graphs the encoding speed (as a multiple of real time) and JS-heap memory use. Browsers do not expose raw CPU percentage to web pages, so encoding speed stands in as the workload indicator.

Compress Video in Your Browser

Shrink MP4, MOV, MKV and WebM files with adjustable quality and resolution — right in your browser, and your video never leaves your device.

The Video Compressor runs entirely in your browser. Your video is decoded and re-encoded on your own device and is never uploaded to ArrayKit — the file you load never leaves your computer.

Open the Image Optimizer

About Video Compressor

Video Compressor shrinks large video files right in your browser — the video is read from your device, re-encoded locally, and never uploaded. Drop in an MP4, MOV, MKV, WebM, or AVI, pick a target quality, resolution, and output format (MP4 or WebM), and the tool compresses it on your own machine. There is no imposed file-size limit, so it works on clips of any length, though bigger files use more CPU and memory and take longer because everything runs in a single browser tab. A live activity monitor graphs encoding speed and memory use while it works, and you can cancel any time. Built for anyone who needs a smaller video to email, upload, or embed without installing software.

Features

Re-encodes video locally in your browser — nothing is uploaded
Output to MP4 for wide compatibility or WebM for smaller files
Adjustable quality via a CRF slider, from higher quality to smaller file
Downscale to 1080p, 720p or 480p, or keep the original resolution
Optionally strip the audio track or cap the frame rate at 24 fps
Live activity monitor graphs encoding speed and memory use as it runs
No imposed file-size limit, and you can cancel a long run at any time
Preview the result in the page and download it, or recompress with new settings

How to use the Video Compressor

Drop a video file onto the page or click to choose one
Pick an output format, a target resolution, and a quality (CRF) value
Click Compress video and watch the live progress and activity graphs
Preview the compressed video and download it to your device

Example

Input

1080p  ·  CRF 28  ·  MP4

Output

84.2 MB  →  19.7 MB   (77% smaller)

A typical result — a 1080p clip re-encoded to MP4 entirely in the browser.

Common errors & troubleshooting

Compression is very slow on a big or long video. — Everything runs in a single browser tab. Downscale the resolution (for example to 720p), choose MP4, or cap the frame rate to speed it up.
The browser tab runs out of memory and the run fails. — Very large videos can exhaust the browser's memory because everything runs locally. Try a lower resolution, split the clip into shorter parts, or use MP4 instead of WebM.
The compressed file is larger than the original. — Your source is already efficiently encoded. Raise the CRF value for a smaller file, lower the resolution, or remove the audio track.
The video will not load or errors out immediately. — The file may use an unsupported or DRM-protected codec. Try a standard MP4, MOV, MKV, or WebM export from your camera or editor.

Frequently asked questions

Is my video uploaded when I compress it?: No. The Video Compressor runs entirely in your browser. Your video is read from your device, processed locally, and never uploaded to ArrayKit or any server.
Is there a file-size limit for compressing video?: The tool imposes no file-size limit, so you can load clips of any length. The practical ceiling is your device's memory — very large videos use a lot of RAM and CPU because everything runs locally in one browser tab.
Which format makes a video smaller, MP4 or WebM?: WebM usually produces smaller files than MP4 at the same quality, but it encodes noticeably slower in the browser. MP4 is faster and plays almost everywhere, so it is the best default.
What does the CRF quality slider do?: CRF (Constant Rate Factor) controls the quality-to-size trade-off. A lower CRF keeps more quality and produces a bigger file; a higher CRF compresses harder for a smaller file. Around 28 is a good balance for MP4.
Why does compressing a large video take so long?: Compression happens on your own device in a single browser tab, so it cannot tap all your CPU cores the way installed software would. Downscaling the resolution, capping the frame rate, or choosing MP4 speeds things up.
Can I see how hard my computer is working?: Yes. While compressing, a live monitor graphs the encoding speed (as a multiple of real time) and JS-heap memory use. Browsers do not expose raw CPU percentage to web pages, so encoding speed stands in as the workload indicator.

Related tools

Image Optimizer — Re-encode and shrink images (JPEG/WebP/PNG), optionally resizing.
Image Format Converter — Convert images between PNG, JPEG and WebP entirely in your browser.
Compress PDF — Shrink a PDF by re-rendering each page to a JPEG at a chosen quality and resolution.
EXIF Viewer & Remover — View and strip EXIF metadata (including GPS) from photos — nothing is uploaded.
SVG Optimizer — Minify SVG — strip comments, metadata and editor cruft, and collapse whitespace.
Base64 Image Encoder / Decoder — Convert images to Base64 Data URIs with ready-made HTML and CSS snippets, or decode a Data URI back to a downloadable image.