Merge Audio: MP3 Joiner

Merge Audio joins several audio files into one. When the sources are compatible with each other, the sound is copied exactly as it is: never compressed a second time, with no quality loss.

That is the difference. Tools of this kind normally re-encode every time, and the loss is discovered when it is too late to undo. Here the strategy is decided before a single byte is written, and the verdict appears on screen before you export. If re-encoding is needed, the app names the track that causes it and the reason: a different sample rate, a different channel count, another codec, or a setting that requires processing.

JOIN WITHOUT QUALITY LOSS
- MP3 frames are copied one by one; AAC or ALAC packets move into a new container.
- The finished file sounds the same as the originals.
- An honest note: every seam keeps the padding added by the original encoder, a few hundredths of a second. It is inaudible in speech, chapters and podcasts; truly gapless music is better re-encoded.

TRIM ON THE REAL WAVEFORM
- Tap a track and set its start and end with two handles over its waveform.
- Trimming does not re-encode either: whole frames are dropped and the rest is copied byte for byte.
- The cut snaps to the nearest complete frame.

OUTPUT FORMATS
MP3, M4A (AAC), M4B audiobook, WAV, FLAC and Ogg Opus. Automatic mode keeps the source format, which is what makes the lossless path possible. Bitrate, sample rate and channels can also be set by hand.

M4B AUDIOBOOKS
Each track becomes a chapter with an editable title. Title, author, album and cover art can be added.

PER-TRACK ADJUSTMENTS
- Gain in decibels.
- Fade in and fade out.
- Transition into the next track: direct join, silence or crossfade.
- Loudness matching at -16 LUFS with true peaks limited to -1 dBTP, per track or treating everything as one program.

HOW IT WORKS
- Pick the files, drag them into order, undo if you change your mind.
- Listen to the mix and to the result inside the app.
- Export with visible progress and cancel whenever you want.
- Save the file or share it.
- History keeps the date, tracks, duration, size and whether the join was lossless.

EVERYTHING ON YOUR DEVICE
Processing happens entirely on your phone or tablet. No files, names, paths or history are uploaded. It works without a connection, contains no advertising and sends no analytics or tracking data. Only the files you pick are read, and no account is required.

MADE FOR
Podcasts and interviews, audiobooks and chapters, voice notes and long messages, recorded lectures and talks, music takes that run one into the next.

Open-source components: LAME, FLAC, Opus and libopusenc, with their licenses and source included in the project.