What is a .zloop file?
A .zloop file is a song saved by Loop by Zaweba: a ZIP holding song.json plus an audio folder with your recordings and samples as float WAV.
A .zloop file is a song saved by Loop by Zaweba, the free offline music maker for Windows. Inside, it is an ordinary ZIP archive holding a file called song.json, which describes the song, and an audio folder holding any recordings and samples the song uses, stored as float WAV. To open one, open it in Loop, which is the program that makes them.
That covers the quick answer. Below is what lives inside the file, how saving works, and how to share a song with someone else.
What is inside
The song.json part is the arrangement: the tracks, the clips on the grid, the notes, the instruments and their settings, the mixer and effects, and the automation. It is text, which is why it stays small even for a long song.
The audio folder holds the parts that can't be written down as notes. When you record your voice or a guitar onto an audio track, each recording ends up here, and so do the samples you drop onto a sampler track. They are kept as float WAV, so nothing is lost by squeezing them down.
Because the whole thing is one ZIP, a song travels as a single file. You don't have to remember to copy a folder of recordings alongside it.
Saving and opening
File > Save (Ctrl+S) writes the .zloop, and Save as (Ctrl+Shift+S) writes a copy under a new name, which is the easy way to keep an earlier version before you try something drastic. File > Open recent lists the songs you had open last.
Saves are atomic. In plain terms, Loop writes the new file completely before it replaces the old one, so a power cut or crash halfway through a save leaves you with the previous version intact rather than a broken file.
Sharing a song
If a friend has Loop, send them the .zloop and they can open it, play it and carry on working on it. Any recordings and samples you used go with it inside the file.
If they just want to listen, a .zloop is the wrong thing to send. Export instead. File > Export gives WAV (16 or 24 bit), MP3 at 320 kbit/s or OGG Vorbis, for the whole song or the loop region. For a friend who uses another music program, File > Export > Stems writes one 24-bit WAV per chosen track, and File > Export > MIDI file writes a type-1 .mid with tempo, track names and General MIDI programs.
Looking inside it yourself
Because it is a ZIP, you can make a copy, rename it to end in .zip and open it with any archive tool to see the song.json and the audio folder. The format is documented in FORMAT.md, which comes with Loop, so anyone who wants to write a tool that reads Loop songs has the details.
Do that on a copy, though. Editing song.json by hand and zipping it back up is a good way to make a song that won't open, and there is little in there you can't change more safely inside the app.
Your own loops are kept separately
One thing that is not inside a .zloop is your My loops library. Riffs you save and audio loops you add with File > Add an audio loop live in the app's data folder as .wav plus .json files. A song that uses one of them carries the audio it needs, but the library itself stays on your computer, ready for the next song.
Keeping songs safe
Since everything is stored on your own computer, with no account and no cloud, backups are up to you. Keep your .zloop files in a folder that is included in whatever backup you already use, and the whole of a song, recordings and all, is covered by that one file.
