Are my audio files uploaded to a server?
No. Decoding, mixing, crossfading, and encoding all run inside your browser using the WebCodecs API. Files never leave your device.
Which formats can I merge?
MP3, WAV, M4A, AAC, OGG (Vorbis/Opus), FLAC — any audio file your browser can decode. Files with different sample rates and channel counts are auto-resampled to a common target.
Which output formats can I export?
MP3, WAV, FLAC, OGG (Vorbis), Opus, AAC (ADTS), and M4A. Codecs your browser cannot encode are greyed out in the format dropdown.
What does Crossfade do?
Crossfade overlaps the tail of one track with the head of the next: the outgoing track fades out while the incoming track fades in. Pick 0 for hard cuts or 0.5–3 seconds for smooth transitions.
Can I reorder tracks?
Yes. Drag the grip handle on the left of each row to reorder, or use Move up / Move down in the row menu.
Why is one of the formats greyed out?
Your browser cannot encode that codec. MP3 encoding in particular is not native in every browser. Use Chrome or Edge for the broadest coverage, or pick another format.
What is the maximum size?
2 GB per file, up to 30 tracks per merge. Decoding streams samples through memory rather than buffering the whole file.
Will the merged file be louder than the originals?
Crossfade overlaps fade in and fade out cleanly with equal-power ramps, so the perceived loudness stays even. No automatic normalization is applied.