Guide
Joining audio files with gaps, crossfades and matching formats
Podcasts arrive as an intro, a conversation and an outro. A course is recorded lesson by lesson. A song is rehearsed in sections. At some point the pieces have to become one file, and doing it in a full editing program is more work than the job deserves. This page takes the files you drop in, puts them in your order, and writes a single file, with the choice of a pause or a smooth blend between each pair.
How the files are brought together
Each file is read by your browser, which decodes MP3, AAC, OGG, FLAC, WAV and WebM sound. WAV files are read at their own sample rate. The first file in the list sets the sample rate of the result, and every other file is resampled to match with a high-quality windowed-sinc filter, which avoids the aliasing a cheap resampler creates. Channels are conformed too: a mono file becomes two identical channels when joined with stereo, so it is heard in the centre.
A worked example
Press Sample to load two WAV files, part-one.wav and part-two.wav, each 689 KB and four seconds long (the second is the first played backwards). With a gap of 0 and a crossfade of 0, Join 2 files writes merged.wav with 352,800 frames at 44,100 Hz: exactly eight seconds, since 176,400 + 176,400 = 352,800. Set the gap to 0.5 and the result is 8.5 seconds. Set the gap to 0 and the crossfade to 1 second and the two clips overlap for one second, giving 7.0 seconds in total. The size panel shows about 1.3 MB for the eight-second file.
Gap or crossfade
A gap is a period of silence and is the right choice for separate items such as tracks of an album or chapters of a talk. A crossfade blends the end of one clip into the start of the next and suits continuous material such as two takes of the same music or ambience. The fade is equal-power: one clip falls with a cosine curve while the next rises with a sine curve, so the combined loudness holds steady through the overlap. The page ignores the crossfade whenever the gap is above zero.
Order and editing the list
Drag a file up or down, or use its arrows, to change the order, and remove one with the cross. Add more files at any time by dropping them on the box again. The list shows each file’s size; the length of every file appears in the result summary. Changing any setting clears the previous result so that the download always matches what you see.
Edge cases
A crossfade cannot be longer than half the shorter of the two files, so a one-second jingle limits the blend to half a second. Files with a different bit depth or format do not matter, because everything is converted to floating point. Very long files need memory, since every sample is held uncompressed while joining. Level differences are not corrected, so a quiet file stays quiet; use the LUFS meter and the booster beforehand if they must match.
Limits
MP3 output is not provided; choose WAV for editing, AAC in M4A for the widest playback or Opus in WebM for small speech files. The tool joins whole files and cannot trim them; cut each clip first with the audio cutter if you need only part. The result is made on your device and nothing is uploaded.
Related tools
- Audio Cutter trims each piece before you join them.
- Audio Converter changes the format of the joined file.
- Audio Volume Booster & Peak Normalizer brings quiet pieces up to the same level.
- Voice Recorder records the pieces to join.
Checked against the current version of the Merge & Join Audio Files on .