Free online MKV to 3GPP converter

Older mobile phones, 3G video systems, and legacy software may require video in a 3GPP (.3gp) container instead of MKV. Converting is also useful when a smaller, simpler file is needed for transmission or playback on hardware that does not support Matroska.

What the MKV format is

MKV, or Matroska Video, is an open container that can hold video, multiple audio tracks, subtitles, chapters, menus, and metadata in one file. It is common for high-definition movie releases, screen recordings, downloaded video, and archival copies because it supports modern codecs such as H.264, H.265/HEVC, VP9, and AV1.

Programs including OBS Studio, MakeMKV, HandBrake, FFmpeg, and many Blu-ray or DVD tools can create MKV files. You may encounter them when a video contains several selectable audio or subtitle tracks, since MKV preserves those streams more flexibly than older mobile-video containers.

What the 3GPP format is

3GPP is a multimedia container standardized for third-generation mobile networks; video files usually use the .3gp extension. It was designed for mobile phones and low-bandwidth transmission, so it commonly contains H.263, MPEG-4 Part 2, or H.264 video with AMR-NB, AAC, or related audio.

A 3GP file is appropriate for older phones, embedded mobile-video systems, legacy messaging workflows, and applications that explicitly accept 3GPP but reject MKV. Its usual advantages are modest file size, simple stream layouts, and compatibility with older mobile hardware. It does not preserve MKV features such as multiple subtitle tracks, chapters, attachments, or several selectable audio streams reliably.

How to convert MKV to 3GPP

Using the 101convert online converter

You can convert the file on the 101convert.com website for free without installing software. Open the video converter, select the MKV file, choose 3GPP or .3gp as the output format, start the conversion, and download the resulting file when processing finishes. Use a short, non-sensitive video if the source contains private material.

Using FFmpeg

FFmpeg is suitable when you need repeatable settings or local processing. Run this command in a terminal:

ffmpeg -i input.mkv -c:v libx264 -profile:v baseline -level 3.0 -pix_fmt yuv420p -vf "scale=640:-2" -c:a aac -ar 8000 -ac 1 -b:a 24k -f 3gp output.3gp

Replace input.mkv with the source filename and output.3gp with the desired output name. The command encodes H.264 video using a Baseline profile, limits the frame size to 640 pixels wide, and creates low-bandwidth mono AAC audio. Remove the -vf "scale=640:-2" option to retain the source dimensions, provided the target device supports them.

If the target is a particularly old phone, MPEG-4 Part 2 video may be more compatible:

ffmpeg -i input.mkv -c:v mpeg4 -vtag mp4v -b:v 500k -vf "scale=320:-2" -c:a aac -ar 8000 -ac 1 -b:a 24k -f 3gp output.3gp

To inspect the source streams before conversion, use ffprobe input.mkv. If the MKV already contains a 3GP-compatible video and audio combination, a remux may avoid quality loss, although compatibility depends on the streams:

ffmpeg -i input.mkv -map 0:v:0 -map 0:a:0 -c copy -f 3gp output.3gp

Transcoding is normally required because MKV files often contain HEVC, AV1, DTS, or other streams that a 3GPP player cannot decode.

Quality and compatibility limitations

Conversion from a modern MKV to a low-bandwidth 3GP usually requires re-encoding, so some detail is lost. Lowering resolution, frame rate, and video bitrate reduces the file size but also reduces sharpness and motion quality; test the output on the intended phone or application.

Many older devices expect a 3GP file with a small frame size such as 176×144 or 320×240, a low frame rate, and AMR-NB audio rather than AAC. FFmpeg builds differ in AMR encoder support, so an AMR-specific output may require an installed external codec or a compatible build. 3GP also generally carries one selected video stream and one selected audio stream; use -map 0:v:0 -map 0:a:0 when the MKV contains multiple alternatives.