merge MP3 files online
Joining MP3 at the byte level, without decoding, leaves the second track's header stuck in the middle of the final file, which most players either misread or simply ignore from that point on. This tool decodes each MP3 to PCM samples, concatenates the buffers and re-exports, by default at MP3 128kbps, even when the loaded files were WAV, and without trying to guess a format from the first file's extension.
The conversion uses a sinc filter with a 16-sample half-width, not simple linear interpolation, so the treble in ep1 and ep3 does not pick up metallic artifacts when upsampled.
Crossfade can never exceed the shorter of the two neighbouring tracks, otherwise the jingle would disappear inside the overlap.
The downmix sums the centre and surround channels into left and right using the same equations the Web Audio API uses, this tool's MP3 encoder does not work with more than 2 channels.
Crossfade is a transition technique where the end of one track fades out while the beginning of the next fades in, creating a smooth overlap. It is ideal for continuous music mixes, soundtracks, or podcasts where abrupt cuts would sound jarring.
MP3 at 128kbps by default, even when every loaded track is WAV, the Audio Joiner does not detect the format from the first file's extension the way the Audio Trimmer does. You can switch to WAV or to MP3 192/320kbps before exporting, if you need more quality or a lossless file.
Not necessarily. The real overlap at each join is the smaller value between the requested crossfade and the duration of each of the two neighbouring tracks. A 0.4s jingle between 30s and 40s blocks, with 3s of crossfade requested, ends up capped at 0.4s of overlap on both sides, because the whole jingle cannot hold a 3s overlap.
The lower-rate track is resampled up, to the highest rate present among the loaded files, never the other way around, so no track loses bandwidth because of the join. Resampling uses a Blackman-windowed sinc filter, the same kind of band-limited filter that avoids the aliasing typical of a simple linear-interpolation conversion.
Your files are processed locally in the browser. No data is sent to any server.