Free online MKV to 3G2 converter

A legacy CDMA phone, handset video tool, or messaging system may require 3G2 instead of an MKV file. You can convert the video on 101convert.com for free without installing software, or use FFmpeg locally for codec and quality control.

What the MKV format is

MKV is the Matroska Video container, identified by the .mkv extension. It can store video, multiple audio tracks, subtitles, chapters, attachments, and metadata in one file.

MKV does not define a single video or audio codec; common combinations include H.264 or H.265 video with AAC, AC-3, or Opus audio. OBS Studio, MakeMKV, HandBrake, FFmpeg, screen-recording tools, and video editors commonly create MKV files. You also encounter MKV when downloading archived video, backing up Blu-ray content, or receiving a file intended for VLC, mpv, or another modern media player.

What the 3G2 format is

3G2 is the 3GPP2 multimedia container developed for CDMA mobile networks. Files normally use the .3g2 extension and can contain mobile-oriented video such as H.263 or MPEG-4 Part 2, with AAC or AMR audio.

The format is useful for older CDMA phones, legacy handset software, and systems that recognize 3GPP2 files but reject MKV. Its smaller files and relatively simple codec combinations suited limited mobile storage and bandwidth. Modern phones, browsers, and messaging applications generally prefer MP4, so 3G2 should be selected for a specific compatibility requirement rather than general distribution.

How to convert MKV to 3G2

Using 101convert.com

1. Open the MKV-to-3G2 converter on 101convert.com.
2. Select the .mkv file.
3. Choose 3G2 as the output format and set resolution, frame rate, or bitrate if those options are available.
4. Start the conversion and download the resulting .3g2 file.
5. Test the file on the target phone or application; older devices may accept only particular resolutions, frame rates, or audio codecs.

Using FFmpeg

Install FFmpeg, open a terminal in the folder containing the source file, and run:

ffmpeg -i input.mkv -c:v mpeg4 -q:v 5 -c:a aac -b:a 64k -ar 44100 -ac 2 output.3g2

This command decodes the MKV streams, re-encodes video as MPEG-4 Part 2, encodes stereo AAC audio at 64 kbps, and writes a 3G2 container. Replace input.mkv and output.3g2 with the actual filenames.

For a low-resolution legacy handset, specify a smaller frame size and frame rate:

ffmpeg -i input.mkv -vf "scale=320:240:force_original_aspect_ratio=decrease,fps=15" -c:v mpeg4 -q:v 6 -c:a aac -b:a 48k -ar 22050 -ac 1 output.3g2

Check whether the installed FFmpeg build supports the required encoders and container with ffmpeg -formats and ffmpeg -encoders. If the destination specifically requires AMR-NB audio, use an FFmpeg build that provides an AMR-NB encoder and replace the audio options with the encoder and sampling rate required by that device.

Quality and compatibility limitations

Changing the container alone is usually insufficient because 3G2 devices often reject the H.265, VP9, Opus, or high-profile H.264 streams commonly found in MKV files. The conversion normally requires re-encoding, which reduces quality and can remove extra audio tracks, subtitles, chapters, attachments, or metadata.

Use the target device's documented limits for resolution, frame rate, bitrate, codec, and audio channels. A 3G2 file may be technically valid but still fail on a phone that expects H.263 video, AMR-NB mono audio, a specific frame size, or an older 3GPP2 profile. Keep the original MKV because conversion to the lower-capability 3G2 format is generally lossy.