MP4 is the file most people can open
MP4 is the file you can hand to almost anyone in 2026. MOV, MKV, WEBM, AVI, and old phone formats are why the other tools exist. Converting a video re-encodes it on your computer or phone. The first run downloads the converter, so it is slower than changing an image.
If you only need the sound, extract it instead of keeping a silent picture. If the clip is too long, trim before you compress. Scaling a small video to HD does not make it sharp.
If you already know the job, start with AVI to MP4 or MP4 to MOV.
Every format on the site is listed from the homepage.
The first run is the slow one
Open the tool that names your two formats and read what the download will contain before you delete the original. If a result does not match that description, tell us.
Re-encode, or do not bother
Most pages that advertise MP4 to MKV on the wider web promise a lossless remux that keeps subtitles and extra audio. This site does not do that. The browser re-encodes. MP4 to MKV writes MPEG-4 video and AAC audio and drops subtitle tracks. MP4 to AVI writes MPEG-4 video and MP3 audio. WEBM uses VP8. If you only needed to change the box and keep every track, use a desktop stream copy or MKVToolNix. Use these pages when a player simply needs a file it will open and you can accept a new encode.
MP4 remains the file phones and social apps accept in 2026. MOV from an iPhone, MKV from a download, WEBM from a screen capture, and old AVI, WMV, FLV, or 3GP files are why the other tools exist. Quality cannot beat the clip you started with. The first run downloads the converter. Stay on the tab. Long files belong on a computer, not a phone.
Trim before you compress if you only need a minute. Video to HD scales toward 720p height. It does not create a 1080p restoration. Extract audio if you do not need the picture. A few targets, including VOB and a reliable WMV encode, are not available and the page says so.
Decide whether you need a new codec or only a new container. A desktop remux is the right answer when the video is already H.264, the audio is already AAC, and you must keep subtitles. These browser tools are the right answer when a player refuses the file and a fresh encode is acceptable. Test one minute. Watch it with sound. Then run the full clip on a computer, not on a phone that will run out of memory.
One minute before the full file
Cut a short section or use a one minute clip the first time. Watch it with sound on the device that rejected the original. If that works, run the full file on a computer. Phones run out of memory on long encodes, and the first run also downloads the converter. Subtitles and extra languages are not kept. If you needed them, use a desktop remux instead of these pages.
Write down the player that failed and the exact message if there was one. "Will not open" and "opens without sound" are different faults. The second one can be an audio codec problem. The first one can be the container. The tool page you pick should match that fault. Converting everything to MP4 is reasonable for sharing. It is a waste if the editor already opened the file and you only disliked the name.