Audio Joiner
Join several audio files into one, in the order you choose. Runs in your browser, nothing is uploaded.
Everything runs in your browser. Your audio is never uploaded, and nothing is stored.
How to use it
Drop two or more audio files onto the box, or tap it to pick them. Add more at any point and they go on the end. Use Up and Down to set the order before joining. The number in front of each file is the order it will play in. Files that share a format are stitched by copying the streams, which is near instant and loses no quality. A mix of formats has to be re-encoded to MP3 instead, which takes longer and costs a little quality. The first run downloads a 31 MB engine. That happens once and is then cached.
Questions
Is my audio uploaded anywhere?
No. The joining happens inside your browser using a WebAssembly build of ffmpeg. The files never leave your device, which is why there is no size limit and no sign-up.
Why did mine have to be re-encoded?
Because the files were not all the same format. Matching files can be copied end to end untouched, a mix cannot, so everything is converted to MP3 at 192k instead.
Does joining lose quality?
Not when the formats match, since the original data is passed straight through. In re-encode mode there is a small loss, as with any re-encode.
Can I add a gap between tracks?
Not yet. The files are joined end to end with no silence in between. Add a short silent file to the list if you need a gap.
How many files can I join?
No limit is set, but everything is held in memory. A phone will struggle once the total gets large, so work in batches if that happens.