Free online KUX to 3GPP converter

A KUX file may not open in a phone, editor, or player that expects the 3GPP container. Converting it produces a .3gp video compatible with many older mobile devices and software that supports MPEG-4 or H.263-based 3GPP files.

What the KUX format is

KUX is a proprietary video container associated with Youku, a Chinese video platform. Youku desktop software and download tools may save offline or downloaded videos as .kux files instead of common containers such as MP4.

A KUX file can contain platform-specific metadata, segmentation, or protection that prevents ordinary media players and general-purpose converters from reading it directly. The extension alone does not guarantee that the file can be converted; access rights and the particular KUX variant also matter.

What the 3GPP format is

3GPP video normally uses the .3gp extension and was designed for mobile networks and phones. Common streams include H.263 or MPEG-4 video with AMR or AAC audio, although compatibility depends on the device and the encoding profile.

3GP files can be smaller than high-quality modern video files because they commonly use low resolutions, low frame rates, and narrow audio bandwidth. The format is useful when an older phone, embedded player, messaging system, or legacy editing application specifically requires 3GPP.

How to actually convert KUX to 3GPP

The built-in converter on 101convert.com can process this conversion without installing software:

1. Open the KUX-to-3GPP converter on 101convert.com.
2. Select or drop the source .kux file.
3. Choose 3GPP or .3gp as the output format.
4. Start the conversion and save the resulting .3gp file when processing finishes.

If the service cannot read the file, first open it with the Youku software that created the download and use an available export or standard-format download option. A protected or incomplete offline download may not be convertible.

For a KUX file that has already been exported to a readable format such as MP4, FFmpeg can create a broadly compatible 3GP file:

ffmpeg -i input.mp4 -c:v libx264 -profile:v baseline -level 1.2 -pix_fmt yuv420p -vf scale=176:-2 -r 15 -c:a aac -ar 8000 -ac 1 -b:a 24k output.3gp

Replace input.mp4 with the exported source filename. The command uses a 176-pixel-wide image and a 15 fps frame rate for older mobile hardware; increase the scale and bitrate only when the target device supports them.

Quality and compatibility limitations

Conversion does not improve the source quality. Re-encoding KUX video to low-bitrate 3GP can reduce detail, introduce motion artifacts, and remove multichannel audio. Test the output on the intended device because some older phones require H.263 video and AMR-NB audio rather than H.264 and AAC.

A KUX file protected by Youku's download system may be playable only through authorized Youku software. Do not bypass encryption or access controls; use an authorized export or a source file that you are permitted to convert.