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Kilnfile

MOV to MP4

Turn QuickTime MOV files into MP4 that plays anywhere, in seconds, without leaving your browser.

Processed on your device, nothing uploadedLast updated

To convert MOV to MP4, drop the MOV file into the MOV to MP4 tool, leave Method on Remux and click Convert to MP4; the MP4 downloads in seconds with no quality loss. Remux copies the H.264 and AAC streams into an MP4 container. Choose Re-encode to H.264 if the MOV holds HEVC and needs to play on older devices.

Your file stays in this tab.On your device
Options

Remux keeps the original video stream. Use re-encode if the file was HEVC/H.265 and will not play elsewhere.

Add several files to get a single ZIP back.

FFmpeg (about 30 MB) is downloaded once on first use and cached by your browser. Speed depends on your device.

How do I convert MOV to MP4?

  1. Drop your MOV files onto the drop zone, or click to browse. AirDropped and emailed iPhone videos work as they are.
  2. Leave Method set to Remux (seconds, no quality loss) for most files.
  3. Switch to Re-encode to H.264 (universal, slower) only if the video was recorded in HEVC and must play on older devices or in Windows Media Player.
  4. Click Convert to MP4.
  5. Download the MP4, or Download all as ZIP when you converted a batch.

MOV and MP4 are close relatives. Both are containers based on the same QuickTime file structure, and the video inside an iPhone MOV is usually H.264 with AAC audio, which is exactly what MP4 expects. That is why the default Remux method is so fast: FFmpeg runs with -c copy, moving the streams into a new MP4 container without decoding a single frame. A 2 GB holiday video remuxes in a few seconds and the output is bit-for-bit the same picture and sound.

The exception is HEVC, also called H.265. iPhones record in HEVC when Settings > Camera > Formats is set to High Efficiency, which is the default on recent models. An HEVC stream can be remuxed into MP4 perfectly well, but the result only plays where HEVC is supported: modern Macs, iPhones, Windows 11 with the HEVC extension, and recent Android. If the remuxed file shows a black screen or an error elsewhere, run it again with Re-encode to H.264.

Re-encode transcodes the video with libx264 at CRF 23, the FFmpeg default that is visually very close to the source, and encodes audio as AAC at 128 kbps. Because the engine is single-threaded WebAssembly, expect roughly real-time to three times real-time for 720p on a recent laptop, so a 5 minute 4K clip can take 10 to 20 minutes. Phones are slower again. Remux first; only re-encode when you have to.

Everything happens in your browser. FFmpeg (about 30 MB) is downloaded once on first use and cached, and no video is uploaded. Files up to around 1 GB are comfortable on a laptop; the browser's WebAssembly memory limit of about 2 GB is the hard ceiling. For larger files, trim first, or remux on a desktop machine rather than a phone.

How it works: this tool uses FFmpeg compiled to WebAssembly (ffmpeg.wasm), loaded into your browser. No server is involved, so Kilnfile never sees your file. Last reviewed 20 September 2026.

Frequently asked questions

Will converting MOV to MP4 reduce the quality?

Not with Remux, which copies the original video and audio streams unchanged into an MP4 container. Re-encode does recompress the video at CRF 23, which is visually near-identical to the source but not bit-identical. Use Remux unless the file will not play.

Why does my converted MP4 not play on Windows?

The MOV was almost certainly recorded in HEVC (H.265), which Windows only plays with the HEVC Video Extensions installed. Convert again with Re-encode to H.264 and it will play in Windows Media Player, PowerPoint and any browser.

How long does it take?

Remux finishes in seconds regardless of length because nothing is decoded. Re-encode runs at about real-time to 3x real-time for 720p on a recent laptop, slower for 4K and on phones. A 1 minute 1080p clip typically re-encodes in one to two minutes.

Is my video uploaded anywhere?

No. The conversion runs entirely inside your browser using FFmpeg compiled to WebAssembly. The only download is the FFmpeg engine itself, about 30 MB, fetched once and cached.

Can I convert several MOV files at once?

Yes. Drop them all in, click Convert to MP4, and each is processed in order. A Download all as ZIP button appears when more than one file has finished.

Cite this page: “MOV to MP4 Converter: Free, Fast, No Upload”, Kilnfile, https://kilnfile.com/media/mov-to-mp4/

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