Is my video uploaded to a server?

No. The entire conversion happens inside your browser. Your video is read into memory on your own device, re-encoded locally by a WebAssembly build of FFmpeg, and the converted MP4 is handed straight back to you as a download — no byte of the video is ever sent to us or anyone else. This is especially valuable for personal footage; the original never leaves your machine, and only the converted copy is produced. Close the tab and nothing is retained.

Why does converting take a few minutes?

Unlike simply trimming or muting a video, converting re-encodes every single frame into the new format, which is genuinely heavy work — and here it runs on your own device inside a browser tab rather than on a powerful server. A short clip may finish in under a minute, while a longer or higher-resolution video can take several minutes. A live progress bar shows how it is going, and you can cancel at any time. The trade-off is that your video stays completely private.

Will the conversion reduce quality?

There is some re-encoding loss, but it is kept visually minimal. The tool uses a high-quality setting (CRF 23) that most people cannot distinguish from the original in normal viewing, while keeping the file a reasonable size. Converting from a lossless or very high-bitrate source to MP4 is inherently lossy, but the result is tuned to look clean on phones, laptops, and TVs. Converting an already-compressed video does not restore detail that was lost earlier.

Is there a limit on file size?

Yes — 500 MB. Because the work is done entirely by your own device inside a browser tab, the video has to fit in the tab’s memory while it is processed, and very large files would risk crashing the tab. If your video is larger than this, trimming it first or compressing it can bring it under the limit. For most phone clips and downloaded videos, 500 MB is comfortably enough.

Convert

Video Converter

Convert a video to MP4 (H.264) right in your browser. Accepts MOV, WebM, MKV, AVI, and MP4. Plays everywhere. Nothing is uploaded. Free, no signup.

By the Samastam teamLast updated 2026-06-14

Drop a video file here, or click to browse

Everything runs in your browser — nothing is uploaded

A video converter changes a video file into a format that plays everywhere — turning a phone MOV, a downloaded MKV or WebM, or an old AVI into a standard MP4. This tool re-encodes your video to MP4 with H.264 video and AAC audio, the combination supported by virtually every phone, computer, TV, and messaging app, and it does the whole job inside your browser. You pick one video file and download a universally playable MP4. It accepts the formats people actually run into — MOV, WebM, MKV, AVI, and MP4 — and always returns a clean MP4. Because the work happens locally, your video never leaves your device; a personal recording, a downloaded clip, or a family video all stay on your own machine, and only the converted MP4 is produced.

What this is and why it matters

Video formats are a constant source of “why won’t this play?” An iPhone records in MOV, which a Windows laptop or a WhatsApp chat may refuse to accept. A clip downloaded from the web arrives as a WebM or an MKV that a smart TV or a basic media player cannot open. An older camera or an archived family video is an AVI that modern phones no longer handle smoothly. In each case the video itself is fine — it is just wrapped in a container or codec that the device in front of you does not understand. Converting is how a file you already have becomes one that actually plays where you need it.

This tool converts in the browser rather than on a server, for the same privacy reason as the rest of the toolkit. Video is often deeply personal — a family recording, a private moment, unreleased footage — and uploading an entire video to a conversion website just to change its format is slow, data-heavy, and a privacy risk. Here the video is read into memory on your own device, re-encoded locally, and handed straight back. Nothing is transmitted and nothing is stored.

The output is always MP4 with H.264 video and AAC audio, because that combination is the closest thing to a universal standard: it plays on virtually every phone, computer, browser, smart TV, and messaging app without extra software. Rather than offer a confusing matrix of codecs, the tool does the one conversion almost everyone actually wants — “make this play everywhere” — and does it well. Whatever container you start with, you get back a clean, broadly compatible MP4.

How to use this tool

Add your video file. Drag it onto the drop zone above, or click to open the file picker and choose a file from your device. MOV, WebM, MKV, AVI, and MP4 are all accepted. The moment it is selected, the tool reads it locally and shows the file name and its size. Nothing uploads — everything happens on your own machine. Files must be under 500 MB.

Let the engine load on first use. The first time you convert, the tool downloads a one-time engine of about 30 MB into your browser. This happens only once — afterwards it is cached and later conversions start immediately without downloading it again.

Convert to MP4. Press Convert to MP4 and the tool re-encodes your video as a standard H.264/AAC MP4. Because every frame is re-encoded, this can take a few minutes for a longer clip — a live percentage shows the progress, and you can cancel at any time if you change your mind. Keeping the tab open while it works lets it finish as fast as your device allows.

Download your MP4. When it finishes, the tool shows the size of the converted file and offers it for download, named after your original file with an .mp4 extension. If the source had no audio track, you simply get a video-only MP4 — there is nothing extra to configure either way.

Examples and use cases

Making an iPhone MOV play on a Windows laptop

A Mumbai user recorded a video on their iPhone that saved as a .mov, but their office Windows laptop and a WhatsApp web chat would not play or accept it. They drop the file in, convert it to MP4, and get back a standard video that plays in any Windows player and uploads to WhatsApp without complaint. The footage never left their machine.

Opening a downloaded MKV on a smart TV

A Chennai user has an MKV video clip that their smart TV’s built-in player refuses to open. They convert it to MP4 on their laptop, copy it to a USB drive, and the TV plays it immediately — no extra apps or codec packs needed, and nothing uploaded to a conversion site. Because the whole conversion ran on their own computer, even a personally recorded clip never had to be handed to a third-party website just to play on the television.

Putting a WebM clip into a presentation

A Delhi teacher saved a short WebM clip from the web but their presentation software only reliably embeds MP4. They convert the WebM to MP4 in the browser and drop it straight into the slide deck, confident it will play on the classroom projector laptop without a last-minute scramble for a player that supports the original format.

Modernizing an old AVI family video

A Pune user found an old .avi family recording that their current phone struggles to play. They convert it to a modern MP4 on their own computer, after which it plays smoothly on every family member’s phone and can be shared in the family chat — a private archive modernized at home, on their own computer, without ever uploading a personal family memory to some random conversion website.

Frequently asked questions

Is my video uploaded to a server?: No. The entire conversion happens inside your browser. Your video is read into memory on your own device, re-encoded locally by a WebAssembly build of FFmpeg, and the converted MP4 is handed straight back to you as a download — no byte of the video is ever sent to us or anyone else. This is especially valuable for personal footage; the original never leaves your machine, and only the converted copy is produced. Close the tab and nothing is retained.
What can I convert from, and what do I get back?: You can convert from MOV, WebM, MKV, AVI, and MP4 — the formats people most commonly run into. Whatever you put in, the tool returns an MP4 with H.264 video and AAC audio. That combination is the closest thing to a universal video standard, so the result will play on virtually any phone, computer, browser, smart TV, or messaging app without needing extra software or codec packs.
Why does converting take a few minutes?: Unlike simply trimming or muting a video, converting re-encodes every single frame into the new format, which is genuinely heavy work — and here it runs on your own device inside a browser tab rather than on a powerful server. A short clip may finish in under a minute, while a longer or higher-resolution video can take several minutes. A live progress bar shows how it is going, and you can cancel at any time. The trade-off is that your video stays completely private.
Will the conversion reduce quality?: There is some re-encoding loss, but it is kept visually minimal. The tool uses a high-quality setting (CRF 23) that most people cannot distinguish from the original in normal viewing, while keeping the file a reasonable size. Converting from a lossless or very high-bitrate source to MP4 is inherently lossy, but the result is tuned to look clean on phones, laptops, and TVs. Converting an already-compressed video does not restore detail that was lost earlier.
Is there a limit on file size?: Yes — 500 MB. Because the work is done entirely by your own device inside a browser tab, the video has to fit in the tab’s memory while it is processed, and very large files would risk crashing the tab. If your video is larger than this, trimming it first or compressing it can bring it under the limit. For most phone clips and downloaded videos, 500 MB is comfortably enough.