What does this audio merge tool do?
Use this tool to join two or more ready local audio files into one output in the order you choose. It processes the files in your browser with a local WebAssembly build of FFmpeg; source files are read but not modified. The tool joins files sequentially rather than mixing simultaneous tracks.
Files, order, removal, and previews
The picker accepts audio/* files. The drop zone advertises MP3, WAV, FLAC, AAC/M4A, OGG, Opus, and more. Ready rows show a detected duration when available; an em dash appears when duration parsing is unavailable. They also show the codec, sample rate, channel count, and file size. Drag rows to reorder them, or use the up and down arrow controls, whose tooltips are Move up and Move down. Select Remove to discard an unwanted or excluded file, then add another valid file if at least two ready files are required. The boundary preview shows each join and estimates the output duration. When at least two files are ready, the merge starts automatically.
Output settings
- Output format offers MP3, AAC (M4A), FLAC, WAV, OGG Vorbis, and Opus.
- Bitrate appears for lossy formats. It offers 96, 128, 192, 256, and 320 kbps; 192 kbps is selected by default.
- Sample rate offers Keep first file's rate, 22,050 Hz, 32,000 Hz, 44,100 Hz, 48,000 Hz, and 96,000 Hz.
- Channel layout offers Keep first file's layout, Mono, and Stereo. In the merge processing, Mono targets mono; other targets are mapped to stereo, so do not use this control as a guarantee that arbitrary multichannel layouts are preserved.
- Metadata offers Keep first file's tags, Strip all metadata, and Set custom title/artist.
- Normalization is Off by default. The other choices are Streaming (-14 LUFS), Podcast (-16 LUFS), and Broadcast (-23 LUFS). The selected option applies one loudness-normalization filter to the concatenated output, not a separate pass to each source clip.
Boundary between files
Boundary between files offers Back-to-back - no gap, no crossfade, Silence gap, and Crossfade. A selected gap or crossfade is applied between every adjacent pair. Silence gap adds the entered duration only when it is greater than 0 seconds; entering 0 seconds produces back-to-back joining with no added silence. A crossfade overlaps the end of one file with the start of the next; the number field has a visible minimum of 0.1 seconds and no visible maximum. The preview estimates a shorter output with a crossfade and a longer output with a silence gap. An unsuitable duration can cause the merge to fail. Audio is not trimmed automatically unless a crossfade deliberately overlaps content.
Re-encoding and lossless-output limits
The merge always decodes, applies audio filters, and re-encodes the joined stream; it cannot stream-copy multiple sources together. A lossy source remains lossy even when you choose FLAC or WAV. Those are lossless output formats, but they do not guarantee bit-exact or unchanged samples: resampling, channel conversion, a gap or crossfade, normalization, filtering, and re-encoding can alter the output. The implementation recognizes lossless codecs including FLAC, ALAC, several PCM codecs, WavPack, TTA, and APE, but the report's lossless indication is based on detected source codecs and the selected output format. It does not verify source bit depth for bit-exact preservation.
How to merge audio files
- Add at least two audio files by dropping them on the tool or choosing browse files.
- Wait for the files to become ready and resolve any excluded-file errors.
- Drag rows, or use Move up and Move down, to set the join order. Select Remove to discard an unwanted or excluded file; add another valid file if fewer than two ready files remain.
- Review the boundary preview and estimated output duration.
- Choose Output format, Bitrate when shown, Sample rate, Channel layout, Metadata, and Normalization.
- Select a Boundary between files option.
- When at least two files are ready, the tool loads its local audio engine and merges automatically; keep the page open while processing.
- Preview the result and select Download merged audio.
Unsupported files and processing limits
A file with no readable audio track is excluded with the message Could not read an audio track from this file - it is excluded from the merge. Unsupported or corrupt audio can produce Could not read this file - unsupported or corrupt audio data. The implementation does not document a maximum file count, total duration, file size, complete input-codec list, or browser compatibility matrix. A merge can also fail when an input cannot be decoded or a selected processing setting, such as a crossfade duration, is unsuitable.
Frequently asked questions
Does this mix files together or just join them one after another?
It only joins them sequentially, end to end, in the order you set. It never overlaps or mixes files as simultaneous tracks - if you need that, use an audio editor with multi-track mixing instead.
Will the merged file be lossless?
The report bases its lossless indication mainly on the detected source codecs and selected output format. If any source was already lossy, such as MP3, AAC, OGG or Opus, that quality loss cannot be recovered by exporting to FLAC or WAV. FLAC and WAV do not guarantee bit-exact or unchanged samples because the merge still decodes, filters and re-encodes the joined stream.
Does it trim any audio automatically?
No. The full duration of every source file is preserved by default. The only way content overlaps is if you deliberately choose a crossfade, which blends the very end of one file with the very start of the next over the length you specify.
Is my audio uploaded anywhere?
No. The entire merge happens in your browser using a local audio engine. Your files never leave your device.
Is there a limit to how many files I can merge?
The implementation does not document a numeric maximum file count, total duration or file size. You need at least two files with ready audio tracks, and processing happens locally in the browser.