Compress Video Online — Shrink Video Files in Your Browser
Drop a video and make it smaller — no upload, no watermark, no software to install. Choose a quality level (CRF) or a target file size, and the file is re-encoded with FFmpeg WebAssembly right on your device. Output is a broadly compatible H.264 MP4.
How it works
Compress MP4, MKV, MOV and more online
Large video files are awkward: they fill up storage, refuse to attach to email, stall when uploading to chat apps, and bog down older devices. This tool lets you compress video online without sending a single byte to a server. Drop an .mp4, .mkv, .mov or .avi and it is re-encoded to a slimmer H.264 MP4 with AAC audio — the format that plays on virtually every phone, computer and website. It is the fastest way to reduce video file size when you just need a smaller copy.
Two ways to control the size
Quality mode (CRF)
CRF (Constant Rate Factor) tells the encoder how much quality to keep. The same scene always gets a similar quality, so the file size varies with how much detail is in the footage — busy, high-motion video ends up larger than a static talking-head clip. This is the most predictable way to keep a video looking good while still shrinking it, which is why CRF is the default for most people.
Target size mode
Sometimes you have a hard limit: an email attachment cap, a 25 MB message upload, or a fixed slot on a website. In target-size mode you enter the size you want in MB and the tool reads the clip's duration from your device, then works backwards to a video bitrate that should land near your target. It is less precise than CRF (bitrate can only approximate a final size), but it is the right tool when the destination sets the limit.
Resolution, codecs and what the output looks like
The compressor always writes a modern H.264 video stream with AAC audio in an MP4 container. H.264 is the safest choice for compatibility: it plays in browsers, on iOS and Android, in PowerPoint, on smart TVs and on old media players alike. The optional resolution cap lets you trade sharpness for size — a 4K clip capped at 1080p or 720p is dramatically smaller and still looks crisp on laptops and phones, where the extra pixels were never visible anyway.
Audio is re-encoded to AAC at 128 kbps, which is plenty for dialogue, music and ambient sound in a compressed clip. If you would rather keep the original audio track untouched, the Video to MP3 tool can extract it, and for pure format changes without quality loss the Total Video Converter for Mac handles stream-copy remuxing.
Browser compressor vs. desktop software
A browser tool and a desktop app solve the same problem under different constraints. The table below shows where each one wins.
| Aspect | This online compressor | Desktop (Total Video Converter / Player Pro) |
|---|---|---|
| Install required | No — runs in the browser | Yes — Mac app |
| Privacy | Local only, no upload | Local only |
| Speed on 4K / long files | CPU-bound, slower | Hardware-accelerated, fast |
| Batch many files | One at a time | Batch queues |
| Exact target size | Approximate (bitrate) | 2-pass, precise |
| File size limit | ~4 GB tab memory | Disk only |
| Best for | One-off quick shrink | Regular, heavy work |
Common scenarios for compressing a video
Emailing or messaging a clip
Most mail and chat apps reject files over 10–25 MB. Drop the clip in, pick target size mode, set 10 MB, and you get a shareable copy in seconds — without a third-party upload service that would copy your footage to its servers.
Freeing up phone or laptop storage
Recorded meetings, screen captures and phone videos pile up fast. Re-encoding them to H.264 at CRF 28 or capping at 720p can cut the space they use by half or more while staying perfectly watchable.
Preparing a video for a website or course
Web pages should stay light. Compressing embedded demos and lecture clips keeps load times down and bandwidth costs low, and the MP4 output is exactly what HTML5 players expect.
Shrinking before archiving
Long, low-priority recordings do not need to keep every byte. A higher CRF or a resolution cap trims the archive without making the content unwatchable.
Privacy: your video never leaves your device
Every step happens inside your browser tab. When you open a file, the browser reads it into memory; the FFmpeg engine, loaded as WebAssembly, re-encodes it on your CPU; and the result is handed back as a download link that points to data still on your machine. No request carrying your video ever reaches our servers, and there is nothing for us to store or delete. The only network traffic is the page itself plus a one-time download of the FFmpeg engine (about 30 MB) the first time you compress a file; after that it is cached by your browser. You can even disconnect from the internet after the page loads and the tool still works.
Frequently asked questions
Is this video compressor really free and does it upload my file?
Yes, it is completely free with no watermarks, account or size cap. All compression runs locally with FFmpeg WebAssembly, so your video is never uploaded to any server.
What is CRF and which value should I pick?
CRF controls quality vs size. Lower keeps more detail and makes bigger files; higher shrinks more but loses detail. For most videos 23 is balanced, 28 is a smaller good-quality file, and 34 is a tiny shareable file. The tool exposes these as presets.
Can I compress to an exact target file size?
Yes. Switch to target-size mode and enter the size in MB. The tool reads the duration from your device and computes a video bitrate near your target, then re-encodes. If you set a target larger than the original, little or no saving is possible.
Which video formats can I compress?
MP4, MKV, MOV, AVI, WebM, MPEG-TS, FLV, 3GP, OGV and similar. The output is always a compatible H.264 MP4 with AAC audio so the compressed file plays almost anywhere.
Will compressing reduce the quality?
Compression by re-encoding always trades some quality for size — that is how files get smaller. The CRF presets are tuned so 23–28 looks close to the original for typical footage, and a resolution cap can shrink further with little perceived loss on small screens.
Why is compression slower than playing a video?
Re-encoding rewrites every frame with a new codec, which is CPU-heavy. A short clip finishes in seconds; a long 4K file can take minutes inside one browser tab. For regular, heavy compression on a Mac, Total Video Player Pro and Total Video Converter use hardware acceleration and are much faster.
Is there a file size limit?
Because nothing is uploaded, there is no server limit. The practical boundary is device memory — a browser tab is limited to roughly 4 GB, so the tool warns above about 1.5 GB and asks before processing very large files.
What if the compressed file is bigger than the original?
That can happen if you pick a low CRF on already-efficient footage, or set a target size larger than the source. The result panel compares old vs new size so you can see it immediately; if it grew, choose a higher CRF or a smaller target and run again.
Supported formats in detail
The compressor accepts the same broad set of containers as the player: MP4, M4V, MKV, MOV, AVI, WebM, MPEG-TS/M2TS, FLV, OGV, 3GP and more. Internally it handles common video codecs (H.264, HEVC/H.265, VP8, VP9, AV1, MPEG-2/4, DivX, Xvid) and audio codecs (AAC, MP3, AC3, Opus, Vorbis, FLAC), re-encoding them to the H.264/AAC pair that maximises compatibility. The output filename keeps the original base name with a -compressed suffix so you can tell the two apart.
Troubleshooting: when compression does not go as expected
The result is larger than the original
You likely picked a low CRF (18) on footage that was already efficiently encoded, or set a target size above the source. Raise the CRF, add a resolution cap, or lower the target size and try again. The before/after sizes are shown so you can confirm the saving.
Compression is very slow or the tab freezes
Re-encoding is CPU-bound. Long 4K or HEVC clips can take minutes in a single browser tab. Close other tabs, or — for regular work — use a desktop app with hardware encoding. The tool confirms before processing files over 1.5 GB.
The compressed video will not play
The output is standard H.264 MP4, which should play anywhere. If your player is unusual, try again; a damaged source stream can occasionally produce a bad frame. For a guaranteed-playable desktop workflow, the Mac converter handles the same job offline.
I need a different output format, not MP4
This tool always emits H.264 MP4 for maximum compatibility. For MOV, MKV, AVI or device-specific outputs, use the Total Video Converter for Mac, which also supports stream-copy remuxing with zero quality loss.
When to use a desktop converter instead
The online compressor is ideal for a one-off shrink: you have a clip that is too big to send, you want to reclaim some storage, or you need a quick smaller copy without installing anything. It intentionally keeps things simple — one file, a couple of sliders, a download.
If compression is part of your routine — batch-processing a folder of recordings, producing web-ready videos every week, or needing frame-accurate 2-pass control and exact target sizes — a desktop app is the better fit. Total Video Converter for Mac uses your Mac's hardware encoders, handles queues of files, and writes to any format you need, while Total Video Player Pro plays and manages large libraries without the wait. That is exactly what this free tool is here to point you towards.
Need to compress videos regularly on your Mac?
Total Video Converter for Mac uses hardware-accelerated encoding for fast, batch compression to any format — MP4, MOV, MKV, AVI and more — with precise 2-pass control. No browser limits, no waiting on a single CPU core.