Video Converter

About converting video

A video file is two things at once: the streams inside it (the picture, the sound) and the container wrapped around them (.avi, .mkv, .mp4). Most conversion problems are container problems — the picture is perfectly fine, it is just in a box your phone, your editor or your TV refuses to open.

That distinction is why this tool is fast when it can be.

It repacks before it re-encodes

Most converters re-encode everything, every time. That takes minutes, and it costs a generation of quality even when nothing needed changing.

This one looks inside the file first. If the video stream is already legal in the container you asked for — and a great many AVI and MKV files hold ordinary H.264 — it simply moves the streams into the new container. That takes seconds and the result is bit-for-bit the original picture.

Only when the streams genuinely will not fit does it re-encode, and then only the parts that have to change. Sometimes that is the sound alone, and the picture is still passed through untouched.

The result always tells you which happened, so you are never left guessing whether you just lost quality.

What it converts

In: AVI, MKV, MOV, FLV, WMV, MPEG/MPG, 3GP, TS, M4V, OGV, WebM — most things a camera, a phone, a screen recorder or an old hard drive will produce.

Out:

• MP4 — the safe answer. Plays on phones, TVs, editors and every website. Choose this unless you have a reason not to.
• WebM — native to browsers and needs no plugin. For a video going onto a web page. Encoded as VP8, which every browser that supports WebM can play.
• MKV — holds essentially any codec, so it is the container that will accept an unusual file without re-encoding. The trade-off is that fewer devices play it.

Quality and resolution

Quality only matters when re-encoding actually happens. *Good* is the usual choice; *High* for footage you will edit further; *Smaller file* when size beats fidelity.

Resolution lets you drop to 1080p, 720p or 480p on the way through — the quickest way to make a large file manageable. One honest caveat: changing the resolution means re-encoding. Repacking moves streams without touching them, and you cannot resize a picture you are not decoding. The tool says so when you pick one.

Everything happens on your device

The converter is a real video toolchain (ffmpeg) compiled to WebAssembly and run inside your browser. Your video never leaves your machine:

• Private — family footage, client work, recorded meetings stay yours
• No upload wait — a 4 GB AVI starts immediately, because nothing is being sent
• No file size limit from an upload cap
• No queue, no sign-up, no watermark

The engine is about 30 MB and downloads once. Your browser keeps it, so the second conversion starts straight away — even offline. The work runs in a background worker, so you can switch tabs while a long video converts; just keep this one open.

What people convert

• An old AVI from a camcorder or a hard drive that nothing modern will open
• An MKV download that a phone or a smart TV refuses
• FLV or WMV from an archive, into something this decade can play
• A MOV from an iPhone, for someone on Windows
• Footage for an editor that only accepts certain formats
• A video for a web page, as WebM

Good to know

• A file your browser cannot preview still converts — not playing it and not reading it are different things
• Very long or very large videos take a while and use a lot of memory; a phone will struggle where a computer will not
• Repacking cannot fix a damaged file; if a video is corrupt, re-encoding is the better bet
• WebM output is VP8. VP9 would make smaller files, but it exhausts the memory the in-browser engine has available and fails partway through — a file that encodes beats one that does not
• Converting to MP4 sets the file up to start playing before it fully downloads, which matters if it goes on a website
• To make a file smaller rather than change its format, use Compress Video to Size
• To keep only the sound, use MP4 to MP3

How to use it

• Click Click to upload, or drag your video onto the box
• Choose MP4, WebM or MKV
• Leave the quality and resolution alone unless you need to change them
• Leave the repack option ticked — it makes the conversion instant when it can
• Press Convert, play the result, then Download video

Related tools

• WebM to MP4 — the one-click version for WebM
• MOV to MP4 — the one-click version for QuickTime files
• Compress Video to Size — hit a target file size
• Resize Video — change the resolution on its own
• MP4 to MP3 — keep the sound, drop the picture
• Video Editor — trim, add music and overlay clips