tooloora

Merge Audio Files — join tracks into one file

Put several recordings in order, optionally crossfade the transitions and export one file — locally in your browser, no upload.

Runs locally — nothing is uploaded

Drop audio files here or click

MP3, WAV, M4A, OGG or FLAC · several files possible · stays local

Runs locally in your browser – no upload.

Merge audio files into one file

Drop the files, put them in the right order, export — and you have one continuous recording. Merging runs entirely in your browser: nothing is uploaded, and there is no total size limit from a server. Typical cases: an interview recorded in several takes, a lecture in parts, audiobook chapters, voice messages.

Can I mix different formats?

Yes. An MP3, a WAV and an M4A may go into the same output file. Because all parts are decoded first, the tool brings differing sample rates and channel counts to a common format automatically — otherwise parts would play too fast or too slow, or a channel would go missing. The highest sample rate and the largest channel count win, and the conversion runs through the browser's OfflineAudioContext, the same path any Web Audio application takes. A 16 kHz voice memo next to a 44.1 kHz music track is therefore no problem.

Is there a crossfade between the parts?

Yes, up to five seconds — but the default is zero: for interviews, lectures and chapter files you want the hard join, not the radio effect. Where a fade does fit, it follows an equal-power curve built from cosine and sine. Their squares always add up to 1, so the perceived level stays constant through the transition; a linear fade dips audibly in the middle. Every crossfade shortens the result by exactly its own length, and at each transition it is capped at half the shorter neighbour. If one part is noticeably quieter than the next, level it first with the volume tool.

How large can the result get?

If you export to WAV, the format itself is worth a look: a classic WAV file follows the RIFF structure defined by Microsoft and IBM, which stores its lengths in unsigned 32-bit fields — so the file cannot exceed 4 GiB. At CD quality (176,400 bytes per second) that is about 6.7 hours. Extensions such as RF64 were invented precisely to get past this limit.

Honest limits

  • Up to 30 minutes per file, and from about 45 minutes total the tool warns you: the decoded audio lives entirely in memory, roughly 21 MB per stereo minute at 44.1 kHz.
  • No gap between the parts. Without a crossfade they meet hard end to end; there is no adjustable silence in between.
  • Encoded once. Going from lossy sources into a lossy target adds one more compression step; exporting to WAV keeps the joined result lossless.
  • The order is your decision. The tool does not sort by file name or recording time — you set the sequence yourself and see it before exporting.

Frequently asked questions

Are my files uploaded to merge them?

No. All files are decoded and joined in your browser — nothing is transferred, and there is no total size limit imposed by a server.

Can I mix different formats?

Yes. An MP3, a WAV and an M4A can go into one output file. Because they are all decoded first, differing sample rates and mono/stereo mixes are brought to a common format automatically.

Does merging reduce quality?

The result is encoded once. Going from lossy sources into a lossy target adds one more compression step; export as WAV if you need the joined file to stay untouched.

How long may the result be?

All parts together should stay under about 30 minutes, because the decoded audio lives in memory — roughly 21 MB per stereo minute at 44.1 kHz. Also note that a classic WAV file cannot exceed 4 GiB, since RIFF stores its sizes in 32-bit fields; that is about 6.7 hours of CD-quality stereo.

Is there a crossfade?

Yes, up to five seconds, and zero is the default — for interviews, lectures and chapter files a hard join is usually what you want. The fade follows an equal-power curve (cosine and sine), so the perceived level stays constant through the transition instead of dipping in the middle the way a linear fade does. Every crossfade shortens the result by its own length.

What happens if a part is shorter than the crossfade?

The fade is capped at half of the shorter neighbour at each transition, so a two-second file never gets a five-second crossfade. That is done per transition, not globally, so one short clip in the middle does not shorten the fades everywhere else.