Apple Music and iTunes Match include a feature called iCloud Music Library. Here’s what you need to know.

Apple Music may have lots of great songs in its catalog, interesting DJs on Beats 1, and cool experimentation within Connect—but it also has the albatross in the room, iCloud Music Library.

The cloud-based feature has taken a bit of a hit since its launch by users and the press alike—largely because Apple never really made it clear how to use iCloud Music Library properly.

If you’re confused about this option, and whether you should enable it or not, here’s the deal.

What is iCloud Music Library?

It’s Apple’s term for all the music you’ve stored in iCloud.

iTunes Match or Apple Music?

Both. Whether you’ve just subscribed to iTunes Match, Apple Music, or both services, all your iCloud-stored music lives in iCloud Music Library.

Wait, stored? Does it count toward my iCloud storage cost?

Nope. You can store up to 25,000 songs with an iTunes Match or Apple Music subscription—and that limit will increase to 100,000 songs come iOS 9 and OS X El Capitan release time.

What’s the deal with matching, storing, and the like?

When you turn on iCloud Music Library for your Mac, it analyzes all the music in your library to see if Apple has any of your songs in its iTunes Music Store (if you’re using iTunes Match) or Apple Music (if you’re using the eponymous subscription service) catalog.

If it does, it won’t manually upload those tracks to iCloud Music Library; instead, it does something called “matching”: It matches your song with a song from the iTunes Match or Apple Music catalog. When you redownload or stream that song on another device that doesn’t have it locally stored, you’ll download the iTunes Store or Apple Music version (depending on which subscription you have; if you have iTunes Match you should always get the DRM-free version from the iTunes Store).

If Apple can’t find a track from your library in its catalogs, it manually uploads the track as-is to iCloud Music Library. When you redownload it on a different device, you’ll get that original uploaded version, transcoded to AAC format.

Do I need a backup before enabling iCloud Music Library?

Yes. Yes, yes, yes. iCloud Music Library may give you copies of your songs in the cloud, but it is in no way a backup service. (If you’re only using Apple Music, for example, your matched tracks will have DRM on them if you redownload them from iCloud—DRM that will render those tracks inoperable if you ever stop subscribing.)

So please, heed our warning: Make sure you have a complete, local copy of all of your music on your primary computer (or external hard drive) before turning on iCloud Music Library.

If you’ve already enabled it and you don’t have all your music locally on one computer, don’t panic: Get an iTunes Match subscription (if you don’t already have one), make sure your music shows up as Matched or Uploaded and not Apple Music, then download all the tracks you’re missing to your main Mac.

What does iCloud Music Library get me?

A bunch of things! Access to your Mac’s library on any of your other devices (up to 10), for one. If you’re an Apple Music subscriber, it also allows you to add songs and playlists from the subscription catalog to your library; you can then save those tracks for offline play.

Why shouldn’t I use iCloud Music Library?

If you don’t have a backup of your Mac’s library, have lots of tracks with crazy metadata that you’re worried iCloud will mess up, or don’t want to save songs offline from Apple Music, you probably should leave iCloud Music Library turned off.

Can I still use Apple Music without iCloud Music Library?

You bet. You can even use iCloud Music Library with some devices and not others. More info here:

I turned on iCloud Music Library and it ate my library/destroyed everything/aghhhh! Help?!

Deep breaths, pal. Do you have a backup? If so, turn off iCloud Music Library on your Mac and restore your library from that file.

If you don’t have a backup, there are a lot of other things you can try, from chatting with Apple Support to resetting your iCloud Music Library. We suggest checking out our troubleshooting guide linked below if you’ve run into trouble and are backupless:

Any other questions?

Have a question about iCloud Music Library I haven’t covered? Let me know in the comments and I’ll try and get you an answer.

from iMore – The #1 site for iPhone, iPad, Mac, and all things Apple!