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NeedToConvert

Convert Video

Change a video's format so it plays on the device, site or editor you need, without handing the file to a server.

  • Free
  • Private
  • No sign-up
Files are processed on your device and never uploaded.
Drop files here or click to browseAccepts MP4, WebM, MOV, MKV, AVI. Up to 500 MB per file.
Options

The video and audio converter (about 31 MB) downloads the first time you use it, then your browser keeps it. Files over 200 MB may need more memory than your browser allows.

A video that plays perfectly on the phone that recorded it can refuse to open somewhere else. iPhone MOV files trip up older Windows PCs, MKV files will not import into some editors and WebM screen recordings are rejected by certain upload forms. Converting to a widely supported format solves most of these problems.

This converter accepts MP4, MOV, WebM, MKV and AVI and writes MP4, WebM, MOV or AVI. Pick an output format and a quality preset, add one or many files and press Convert. Every file is processed in your browser, and you can download the results one by one or as a single ZIP.

Containers and codecs, in plain terms

The file extension names the container, a wrapper that holds the video stream, the audio stream and their timing. Inside, each stream is compressed by a codec. Compatibility depends on both: a device might open MP4 files yet still fail on one whose video uses a codec it cannot decode.

So this tool always re-encodes into a proven pairing for each container. MP4 and MOV get H.264 video with AAC audio, the most widely playable combination there is. WebM gets VP8 video with Vorbis audio, both open and royalty-free and supported by Chrome, Firefox and Edge. AVI gets MPEG-4 Part 2 video, tagged as Xvid, with MP3 audio, the combination older DVD players, set-top boxes and legacy editing software expect. Resolution and frame rate are kept; if a dimension is an odd number of pixels it is rounded down by one, because these encoders need even sizes.

Typical conversions

MOV to MP4 for sharing and editing

Recent iPhones often record in HEVC inside a MOV container. Converting to MP4 with H.264 makes the clip open on almost any computer, phone, smart TV or video platform, at the cost of a somewhat larger file for the same quality.

MKV or WebM to MP4 for editors and social apps

Many video editors and social upload forms prefer MP4. Converting a screen recording or a downloaded MKV gets it accepted without installing extra codecs.

Anything to AVI for older hardware

Older media players and set-top boxes that predate H.264 often read Xvid AVI files. This is the format to pick when nothing else will play on that device.

Quality presets and speed

For MP4 and MOV, the quality presets map to H.264 constant quality (CRF) values: High is 18, which looks visually lossless for most footage; Balanced is 23, the long-standing default of the x264 encoder; Smaller file is 28, which visibly softens fine detail but can roughly halve the size compared with Balanced. Audio is AAC at 192, 128 or 96 kbps to match. WebM and AVI follow the same three steps with settings suited to their encoders; for VP8 the bitrate ceiling drops from 4 Mbps at High to 800 kbps at Smaller file.

The converter is ffmpeg compiled to WebAssembly. It downloads once, about 31 MB, the first time you press Convert, then your browser keeps it. It runs on a single CPU thread and cannot use the hardware video encoders in your graphics chip, so expect it to be slower than desktop apps such as HandBrake. A minute of 1080p footage can take several minutes, and 4K takes far longer. Each file can be up to 500 MB, and files over 200 MB may run out of memory on phones and in some browsers.

How to use this tool

  1. Drop one or more MP4, MOV, WebM, MKV or AVI files on the box above, or click it to browse.
  2. Under Output format, choose MP4, WebM, MOV or AVI.
  3. Under Quality, choose High, Balanced or Smaller file. Balanced suits most uses.
  4. Press Convert and keep the tab open while the progress bar runs.
  5. Download each converted video, or press Download all (.zip) to save them together.

Limitations

  • Every conversion re-encodes, even MP4 to MP4, so there is always a small quality cost and a file named with -converted.
  • There is no MKV output, and no choice of codec, resolution or frame rate beyond the three presets.
  • One video track and one audio track are kept. Extra audio languages are dropped, and subtitles are not reliably carried over.
  • HDR footage from recent phones is written as standard 8-bit video, so colours may not match the original exactly.

Frequently asked questions

Which format should I choose?

MP4 in almost every case. It plays on Windows, macOS, iOS, Android, smart TVs and every major video site. Pick WebM when a project asks for an open format, MOV for Apple workflows that expect it, and AVI for old players.

Will converting reduce the quality?

Every re-encode loses a little information. At High the difference is very hard to see; at Balanced it is minor for most footage; Smaller file trades visible detail for size. Converting the same clip repeatedly adds up, so always start from the original.

Why is the converted file larger than the original?

Phones often record with HEVC, which compresses better than H.264. Converting to the more compatible H.264 at High or Balanced can therefore produce a bigger file. Choose Smaller file if size matters more than detail.

Can I compress a video with this tool?

Yes, in practice: converting to MP4 with Smaller file usually produces a much lighter file than a phone recording, at reduced sharpness. Cutting the clip shorter with Trim Video first saves even more.

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