Add a pack to your osu! collections

To add a pack to an osu! collection, open the pack on packs and use the "Add to osu! collection" card under its maps. On osu!stable, you load your collection.db and download it back with the pack's maps added. On osu!lazer, you download a small zip and import it with lazer's setup wizard. Your collection.db is read in your browser: packs doesn't upload it or keep it.

An osu! collection is a name and a list of difficulties. osu! doesn't list them by beatmap ID: each difficulty is the MD5 checksum of its .osu file. packs takes those checksums from the map info it already loads for the pack, so it doesn't need your maps or your osu! account.

A difficulty you haven't downloaded yet can still go in a collection. osu! hides it until you have the map, then shows it. The card lists any map it can't add: maps the mirror and osu! don't know, and maps whose info has no checksum.

1. Close osu!. osu!stable saves collection changes a while after you make them, or when it closes, so the file on disk can be behind until then. Keep it closed until the new file is in place.
2. Find your collection.db. It's in your osu! folder, next to osu!.db. On Windows that's %LOCALAPPDATA%\osu! unless you installed osu! somewhere else. The AppData folder is hidden, so paste %LOCALAPPDATA%\osu! into the file picker's address bar to get there. No collection.db yet? Make any collection in osu!, close osu!, then load the file it writes.
3. Load it. On the pack's page, in "Add to osu! collection", pick osu!stable and choose the file.
4. Pick a collection. Choose one you have, or make a new one. A new one is named after the pack, and you can change the name. Typing the exact name of a collection you have adds to that one. Case counts, and so do spaces inside the name.
5. Check the preview. It says how many maps get added and how many are already in the collection.
6. Download collection.db. The download holds all your collections, with this pack's maps added. Nothing else changes, except that empty map entries are left out if the card found any.
7. Swap the file. Keep a copy of your old collection.db, put the new one in the osu! folder named exactly collection.db, and start osu!.

osu! has to stay closed from the moment you load the file until the new one is in place. osu!stable reads collection.db when it starts and saves its own copy later, so it ignores a file swapped while it runs and then writes over it, and a file loaded while it runs can miss your latest changes. If your browser saved the download as collection (1).db, rename it to collection.db.

If you have more collections than the card lists, pick "New collection" and type the exact name of the one you want: the card adds to it.

To add the pack to a second collection, pick it and download again. The second download includes the first change, so only the last file needs to go in the osu! folder.

osu!lazer keeps collections in its own database, which a web page can't open, and it can't export them. It can import a collection.db through its setup wizard, and it merges what it imports into the collection with the same name. So packs gives you a file with just this pack's maps.

1. Name the collection. In "Add to osu! collection", pick osu!lazer and type the collection's name exactly as it shows in lazer. Case and spaces count: any other name makes a new collection.
2. Download the zip. Press "Download zip for osu!lazer".
3. Extract it. You get one folder holding collection.db and an empty osu!.import.cfg. The empty file is what makes lazer accept the folder.
4. Open the setup wizard. In osu!lazer, open Settings, then General, and press "Run setup wizard". Press Next until you reach the Import step.
5. Choose the folder. Pick the extracted folder as the previous osu! install, or drag the folder onto the osu! window. If osu!stable is installed, the field already points at it: change it.
6. Import only collections. Untick Beatmaps, Scores and Skins, leave Collections ticked, and press "Import content from previous version". Wait until lazer says it imported the collections.

An import only adds. Nothing already in lazer is removed or renamed, and importing the same zip twice adds nothing the second time. This works on desktop: osu!lazer on Android and iOS can't import collections.

• You don't have it yet. Download the pack. The map shows up in the collection once osu! has it.
• The map was updated. A collection points at one exact version of a difficulty. packs uses the checksum osu! lists today, so a copy you downloaded before an update, or an older copy on the mirror, may not match. Update the map in osu!, and it shows up.
• packs left it out. The card lists the maps it couldn't add, and why.

packs reads your collection.db in your browser tab. It isn't uploaded, saved or logged, and it's gone when you close the tab.