How to convert a video to MP4 for free, in your browser

How to convert a video to MP4: the short answer

Upload the video, click "Convert and download" and get an MP4 with the same name as the original file. The conversion runs inside your browser, on the whole video and at the same resolution it was recorded in. The file is lightly recompressed, with a quality loss almost invisible to the eye, and comes out ready for WhatsApp, Instagram, YouTube, websites and slideshows. It works with MOV, MKV, AVI, WebM and M4V.

Why MP4 opens everywhere

MP4 is the most widely accepted video format there is: it opens on phones, computers and browsers, and goes through WhatsApp, Instagram and YouTube without complaint. A MOV (the iPhone default), an MKV, an AVI or a WebM tends to get stuck somewhere along the way: the video won't open, only the sound plays, or the app says it doesn't recognize the file. These are the most common signs that it's time to convert:

• WhatsApp won't send the video, or sends it only as a document, with no preview.
• The video opens on your phone but not on someone else's computer.
• The website, form or course platform only accepts .mp4 uploads.
• Your video editor or PowerPoint doesn't recognize the file when you import it.

Convert a video to MP4, step by step

1. Open the Convert video to MP4 tool and upload the video: drag it onto the "Drag your files" area or click "Select files."
2. Check the list: MOV, MKV, AVI, WebM and M4V are accepted. If the file is already .mp4, you'll see "The videos you uploaded are already MP4" and nothing is converted. In a mixed batch, only the files that aren't .mp4 yet are counted on the button.
3. Click "Convert and download" (with several videos the button reads "Convert N videos"). On first use the video engine warms up and may take a few seconds; large videos take longer.
4. Download the MP4: you get one file per uploaded video, with the same name and the .mp4 extension.

What the conversion does (and doesn't do)

• Keeps the resolution and framing: a Full HD video stays Full HD, with no cropping or resizing.
• Recompresses the video into the most compatible standard (H.264 for the picture and AAC for the sound, the same ones phones use). There is a slight quality loss, practically imperceptible.
• Offers no settings: you can't pick a resolution, a quality level or a segment. It's convert and done.
• Doesn't reconvert a file that is already .mp4; if your MP4 won't open somewhere, the format isn't the problem.
• With several videos, each one becomes a separate MP4, downloaded one by one.

If you need the video smaller, compressed or trimmed, this isn't the place: the goal here is only to switch to a format that opens on any device, not to compress it.

What if the video came out mirrored?

Front-camera recordings often come out flipped: text on a shirt or a sign reads backward, as in a mirror. The Flip video tool flips the image horizontally, swapping left and right. And there's a bonus: the result always comes out as MP4, with "-espelhado" added to the name, even when the input is MOV or MKV. So if your video is both mirrored and in the wrong format, one click on "Flip and download" fixes both. For a mirrored photo rather than a video, the path is in how to rotate and flip an image.

Common problems and limits

• It's taking too long: long or 4K videos take several minutes, because the work is done by your own device's processor. Keep the tab open.
• The browser froze: the upload limit is 2 GB per file, but on phones and weak computers memory runs out first. Try a smaller video or a desktop computer.
• Format refused: WMV, FLV, 3GP and TS aren't on the list. Only MOV, MKV, AVI, WebM and M4V.
• A silent video stays silent: if the original has no audio track, the MP4 comes out without sound, and that isn't a defect.
• You see "Could not convert the video.": the file is damaged or uses a compression the engine can't read. Try opening the original in a player; if that fails too, the recording itself is the problem.

Both the MP4 conversion and the flip happen right in your browser: the video is never sent to any server. The only download is the conversion engine, about 9 MB, once, on first use. No app, no account.

With the video in MP4, the "will it open on the other end" worry is gone: it uploads to the site, drops into the presentation and goes through WhatsApp with a preview, not as a document. It's the right format to keep and share. If all you want is the sound, see how to extract the audio from a video and save it as MP3; to join several videos into one, how to merge several videos or several MP3s into one file.