Audio merge — concat multiple files into one
Concatenate multiple audio files via the ffmpeg.wasm concat demuxer. Reorder by drag. Stream copy keeps codec untouched, but all inputs must share the same codec and sample rate.
How to use
Drop two or more audio files. Drag to reorder, then click Merge — ffmpeg.wasm's concat demuxer joins them into one file. Stream copy means no re-encoding, but all inputs must share the same codec, sample rate and channel count.
FAQ
- Is audio uploaded?
- No. ffmpeg.wasm runs inside your browser; audio never leaves your device.
- Why does merging fail?
- Mismatched codec / sample rate / channels. Pre-process with the audio convert tool first.
- Can I crossfade between files?
- Currently it's plain concatenation.
- How long is the output?
- The sum of the inputs' durations.
Related tools
Audio cut — trim a range with no re-encoding
Trim an audio file to a chosen range with ffmpeg.wasm stream copy — no re-encoding, original codec and extension preserved. Cut points snap to the nearest keyframe. Supports batch processing and a single ZIP download.
Audio format convert — MP3 / WAV / M4A / OGG / FLAC
Convert audio files to mp3 / wav / m4a / ogg / flac. ffmpeg.wasm picks an encoder based on the chosen extension and re-encodes the file entirely in your browser. Supports batch processing and a single ZIP download.
Audio channel merge — two mono files into a stereo L + R
Combine two mono audio files (MP3 / WAV / M4A / FLAC / OGG) into one stereo file. The first file becomes the left channel, the second becomes the right; we interleave them and output one stereo WAV / MP3. Useful for putting two-mic interview takes into a single L/R file, faking stereo from a mono source, or reversing audio-channel-split. When lengths differ, truncate to the shorter file or pad the shorter one with silence — your choice. Everything stays in your browser.
BPM auto-detect — estimate the tempo of an audio file
Drop an audio file (MP3 / WAV / M4A / FLAC / OGG) and we estimate the BPM in-browser using a low-pass filter + peak picker + histogram. Great for finding the tempo of a DJ partner track, checking sample packs, matching dance / running cadence, or grabbing a source BPM before running bpm-time-stretch. Half-tempo and double-tempo candidates are also shown so you can override 4-on-the-floor misreads (60 vs. 120). Everything stays in your browser.