Convert Video Online — Change Video Format in Your Browser

How it works

Convert video online without uploading anything

Format problems are stubbornly common. A camera writes a .mov that a Windows editor refuses to open, a downloaded file arrives as .mkv that QuickTime will not touch, or a slide deck only accepts an .mp4. The usual answer is to find a converter, install it, and hope it does not bundle anything else. This page removes that step: drop the file in, choose the container you need, and get a new file back. Because the work happens on your own CPU through FFmpeg compiled to WebAssembly, no server ever sees your footage — there is no upload queue, no registration wall, no watermark and no arbitrary file-size cap imposed by a hosting bill.

Remux versus re-encode: the difference that matters

Remux (stream copy)

Most videos are already compressed with sensible codecs. If your file contains H.264 video and AAC audio, and you want it in a container that accepts H.264 and AAC, then no pixels need to be recalculated at all. A remux simply takes the compressed data out of the old container and writes it into the new one. It finishes in seconds, the picture is bit-for-bit identical to the source, and the file size barely changes. This is why remux is the default and preferred path whenever it is possible.

Re-encode

Sometimes the target genuinely cannot hold what the source carries: WebM containers accept VP8/VP9 and Opus rather than H.264 and AAC, and some legacy AVI players expect MPEG-4 Part 2 video with MP3 audio. In those cases every frame has to be decoded and compressed again. Re-encoding costs time and is the only step where quality can change, which is why the tool exposes a CRF quality level and a resolution cap for it. If you never want re-encoding, choose "Remux only" and the tool will report an honest failure rather than quietly degrading your video.

What Auto mode does

Auto mode runs the cheap, lossless path first and inspects the result. If the container rejects the streams, or FFmpeg reports a problem, it transparently retries with the re-encode profile for the format you chose. You get the best possible outcome without having to know which of the two situations your file falls into.

Convert MOV to MP4

This is the single most requested conversion, and it is usually the easiest one. A MOV from an iPhone, a DSLR or a screen recorder almost always contains H.264 video and AAC audio — exactly the pair MP4 expects. In that case remux mode repackages it in seconds with zero quality loss, and the result plays everywhere: Windows Media Player, Android phones, PowerPoint, web pages, smart TVs and editing tools that never learned to open QuickTime files. If the MOV instead carries Apple ProRes, HEVC or PCM audio, the tool re-encodes to H.264/AAC so the MP4 stays universally playable.

Convert MKV to MP4

Matroska is a flexible container that happily stores almost any codec, which is why it is a favourite for rips and downloads — and why so many devices refuse to open it. Converting MKV to MP4 is the standard fix. When the MKV holds H.264 video with AAC or MP3 audio, remux carries it across untouched; when it holds HEVC, VP9 or lossless FLAC tracks, the tool re-encodes to the H.264/AAC pair that televisions, consoles and mobile players understand. Subtitle and extra audio tracks are preserved on the remux path whenever MP4 supports them.

Convert AVI to MP4

AVI is a legacy container associated with older camcorders and DivX-era downloads, and modern players increasingly struggle with the codecs typically found inside it. Converting AVI to MP4 gives you a file that behaves properly on current hardware and streams over the web. Because AVI frequently wraps MPEG-4 Part 2, DivX or Xvid video rather than H.264, this conversion very often needs the re-encode path — expect it to take longer than a remux and to produce a somewhat different file size.

Convert MP4 to MOV

Going the other way is just as valid. Final Cut Pro, older QuickTime workflows and some broadcast pipelines prefer MOV, and converting an MP4 into a QuickTime container is normally a pure remux: the same H.264 and AAC streams, placed in a .mov wrapper. That means no waiting and no quality change, which is exactly what you want when the only problem is the file extension rather than the content.

Convert MP4 to MKV

MKV is the right target when you want a container that holds everything: multiple audio tracks, chapter markers, soft subtitles in several languages and unusual codecs, all in one file. Converting MP4 to MKV is a straightforward remux in most cases, and it is the usual first step before authoring a multilingual release or archiving a project with all its tracks intact.

Convert video to WebM

WebM is the open, royalty-free format built for the web, using VP9 video and Opus audio. It is an excellent choice for embedding video on a site or shipping alongside an MP4 fallback, because it is small at a given quality and fully open. Converting to WebM always requires re-encoding, since the codecs differ from an MP4's — the tool writes VP9 with Opus, and automatically retries with VP8 and Vorbis if your browser's WebAssembly build reports a problem with the newer encoders.

Convert video to AVI

AVI survives mainly for compatibility with old hardware media players, car stereos, DVD-class set-top boxes and industrial or embedded equipment that was never updated. The tool writes AVI with MPEG-4 Part 2 video and MP3 audio — the combination such devices expect — and falls back to H.264 if that encoder is unavailable. If you are targeting anything made in the last decade, MP4 is almost always the better answer.

Which output format should you choose?

Browser converter versus desktop software

Both approaches convert video, but they are built for different amounts of work. The table below is an honest comparison rather than a sales pitch.

Common situations where this tool helps

A file will not open on the device you have

Someone sends an MKV or an AVI and your player rejects it. Converting to MP4 locally takes a fraction of the time it would take to install and learn new software, and it works on a machine where you have no administrator rights.

You need a specific container for a website or an editor

Many upload forms and editing tools accept only one or two containers. Converting first avoids a failed upload or an import error, and because the remux path is lossless you do not pay a quality penalty for it.

You are preparing an archive

MKV is a strong long-term home for material with several audio tracks and subtitle languages. Converting to MKV before shelving a project keeps everything together in one file that future tools can read.

You were handed a raw camera file

ProRes, HEVC and other capture codecs are excellent for editing and awkward for sharing. Re-encoding to H.264/AAC in an MP4 gives you something you can email, message or post without a second thought.

Privacy: your video never leaves your device

Every stage happens inside your browser tab. When you open a file, the browser reads it into memory; the FFmpeg engine, loaded as WebAssembly, repackages or re-encodes it on your CPU; and the finished file is handed back as a download link that points to data still sitting on your machine. No request carrying your video ever reaches our servers, and there is nothing for us to store or delete afterwards. The only network traffic is the page itself plus a one-time download of the FFmpeg engine (about 30 MB) the first time you convert a file — after that your browser caches it, and you can even disconnect from the internet once the page has loaded and the tool keeps working.

Frequently asked questions

Supported formats in detail

The converter accepts the same broad set of input containers as the rest of the toolset: MP4, M4V, MKV, MOV, AVI, WebM, MPEG-TS/M2TS, FLV, OGV, 3GP, WMV and more. Internally it handles common video codecs (H.264, HEVC/H.265, VP8, VP9, AV1, MPEG-2, MPEG-4 Part 2, DivX, Xvid) and audio codecs (AAC, MP3, AC3, Opus, Vorbis, FLAC, PCM). Output is written back with the codec pair chosen for maximum compatibility in the target container, and the filename keeps the original base name with a -converted suffix so the two files are easy to tell apart.

Troubleshooting: when conversion does not go as expected

"Remux only" failed

That means the target container genuinely cannot store one of the streams in your file — for example converting an H.264 MP4 to WebM, which only accepts VP8/VP9 and Opus or Vorbis. Switch to Auto or "Always re-encode" and the tool will convert the codecs instead of just the container.

Conversion is very slow or the tab becomes unresponsive

Re-encoding is CPU-bound and runs in a single browser tab. Long 4K or HEVC clips can take minutes. Close other tabs, pick a resolution cap, or — for routine work — use a desktop converter with hardware encoding.

The output video will not play

Make sure you are testing with a current player: MP4 output is standard H.264/AAC and should play anywhere. If a legacy device is the target, try AVI (MPEG-4 + MP3) instead. A damaged source stream can also produce an unreadable frame, in which case re-encoding rather than remuxing often repairs the file.

The converted file is larger than the original

This happens on the re-encode path when you pick a low CRF on footage that was already tightly compressed. Choose a higher CRF or add a resolution cap; the result panel shows old versus new size so you can see the difference immediately.

I need a format that is not in the list

This tool focuses on the five containers that cover nearly every real request. For device-specific profiles, DVD and Blu-ray output, audio-only exports or large batch jobs, the Total Video Converter for Mac supports hundreds of presets and hardware acceleration.

When to use a desktop converter instead

The online converter is ideal for a one-off job: a file you cannot open, a container an upload form insists on, or a quick repackage on a computer you do not own. It deliberately stays simple — one file, a few options, a download — and it protects your material by never sending it anywhere.

If conversion is part of your routine, the calculus changes. Batch-processing a folder of recordings, producing web-ready files every week, needing frame-accurate control, hardware acceleration and every output profile under the sun — that is desktop territory. 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 making you convert anything at all. That is exactly what this free tool is here to point you towards.