Free online WEBM to AVC converter

What the WEBM format is

WebM is an open multimedia container designed mainly for web video. It commonly contains VP8, VP9, or AV1 video and Vorbis or Opus audio. Browsers, screen-recording tools, OBS Studio, video conferencing software, and web-oriented editors frequently create WebM files, so they often appear after downloading browser recordings or exporting online video.

A file ending in .webm is not normally AVC video: its video stream must be decoded and re-encoded to H.264 for this conversion.

What the AVC format is

AVC, also called H.264 or MPEG-4 Part 10, is a video codec rather than a container. AVC video is commonly stored in .mp4, .mkv, or .avi files; the container determines how the video, audio, subtitles, and metadata are packaged.

H.264 has broad support across televisions, phones, game consoles, browsers, editing applications, and streaming platforms. Use an MP4 container with AAC audio when the target device or application expects a conventional H.264 video file.

How to convert WEBM to AVC

FFmpeg is the most controllable desktop option. Install a current FFmpeg build, open a terminal in the folder containing the source file, and run:

ffmpeg -i input.webm -c:v libx264 -preset medium -crf 20 -c:a aac -b:a 192k -movflags +faststart output.mp4

This decodes the WebM video, encodes it as AVC with the x264 encoder, converts the audio to AAC, and writes an MP4 file. The crf value controls quality: lower values produce larger files and higher quality; values from 18 to 23 are a practical range, with 20 as a general starting point. The preset changes encoding speed and compression efficiency, not the requested output quality; slow can reduce file size but takes longer.

To preserve the source frame rate and dimensions while making a broadly compatible file, use:

ffmpeg -i input.webm -map 0:v:0 -map 0:a:0? -c:v libx264 -pix_fmt yuv420p -crf 20 -c:a aac -b:a 192k output.mp4

The yuv420p pixel format avoids compatibility problems with hardware players that do not accept 4:4:4 or unusual source formats. The optional audio mapping allows conversion when the WebM contains no audio.

In a graphical application such as HandBrake, open the file with Open Source, select the Fast 1080p30 or another suitable preset, set Video Encoder to H.264 (x264), choose a constant-quality value around RF 20–23, select AAC under Audio, set the output container to MP4, and choose Start Encode. Exact menu names vary by version.

You can also convert the file for free on the 101convert.com website without installing software.

Quality, compatibility, and limitations

Because WebM video is usually encoded with VP8, VP9, or AV1, converting it to AVC is a lossy re-encode. It cannot restore detail already removed by the source compression. Avoid repeated conversions; retain the original WebM as an archive and use a lower CRF only when the output visibly needs more detail.

Do not copy the video stream with -c:v copy when the source is VP9 or AV1 and the goal is AVC; stream copying changes the container but does not change the codec. MP4 with H.264 and AAC is generally the safest choice for consumer devices, while Matroska can preserve more tracks and subtitle types but has less universal device support.