Convert 3GP to MP4

If the video uses H.264 (most later 3GP files do), yes — it transcodes to MP4 cleanly. Very old 3GP using the H.263 codec is the exception the browser may not decode; those are rare now.

No. The transcode runs with WebCodecs on your device, so the video never leaves the browser — no account, no quota, no size limit. Chrome, Edge and Firefox work best.

No — and it is worth setting expectations. 3GP clips from old phones were recorded at low resolution and bitrate, and converting to MP4 changes the container and codec, not the footage that was captured. The result plays and uploads everywhere modern MP4 does, but it will look exactly as sharp as the original 3GP — no detail is invented. What you fix is compatibility, not image quality.

3GP was built for the slow networks and limited phones of its era, using older codecs — often H.263 video and AMR audio — that today players, editors and social uploads have largely dropped. The file is not broken; its formats are simply obsolete. Transcoding to a standard H.264 MP4 puts the same footage into the container and codecs modern software still supports.

Yes — the audio is carried over and re-encoded to AAC alongside the H.264 video, so the MP4 plays with sound on modern devices. Old 3GP audio — often AMR, a narrowband voice codec — is converted too; it will sound the same as the original recording, since converting cannot improve audio that was captured at low quality.