Where apps hide your files
Calibre has no hidden database in your Library folder. Your books live in one ordinary folder with a file called metadata.db at the top, and calibre can tell you where it is.
Calibre's welcome wizard suggests a folder called Calibre Library in your home folder, so unless you changed it on first run, your library is here:
~/Calibre LibraryYou may have picked another folder in the wizard, or switched libraries since, so do not assume. Books inside are sorted into subfolders by author and title, and every library has a file called metadata.db at its top level, which calibre's FAQ says holds the metadata about your books.
The most reliable way to find yours is to ask calibre. Click the toolbar button showing your library's name (Calibre Library by default). With one library it opens the Switch/create library dialog directly; with several it shows a menu where you choose that item. The dialog states where your calibre library is currently located.
If calibre will not open, search the Mac for the one file every library has:
metadata.db| Item | What it is |
|---|---|
metadata.db | The database of titles, authors, tags, ratings and so on. Without it, the folder is just files |
<Author>/<Title (id)>/ | One folder per book. The number in brackets is the book's id in the database |
| The book files | The e-book in each format, named Title - Author plus the extension |
metadata.opf and cover.jpg | Calibre's per-book metadata backup and cover, kept next to the book |
.caltrash | Hidden folder of recently deleted books, emptied after 14 days by default |
metadata_db_prefs_backup.json | A backup of the library's own settings |
Recent versions may also add full-text-search.db (the full-text search index) and a hidden .calnotes folder (notes). The FAQ explains that calibre manages these folders itself, does not let you use your own folder structure, and may delete files or folders you add by hand. Rename and reorganise inside calibre, not in Finder.
open ~/Calibre\ LibraryIf yours is elsewhere, use the path calibre shows, in quotes because the folder name usually contains a space.
Let calibre do it. In Switch/create library, enter a new location and choose Move the current library to new location. Calibre moves the files and updates its setting in one step; the new folder must be empty. That is the safer route for a large library on an external drive.
If you already moved the folder in Finder, use the same dialog with Use a previously existing library at the chosen new location and point it at the folder.
Two cautions from calibre itself. Keep the library on a drive that is mounted when you start calibre. And the FAQ says not to put the library on a networked drive; if you use a syncing tool such as Dropbox, do not run it and calibre at the same time, and the FAQ singles out Google Drive as incompatible. The dialog warns that a network or cloud-synced location is not safe.
The FAQ offers two routes. Right-click the calibre button in the toolbar and choose Export/import all calibre data to export books, settings and plugins, then import them on the new Mac. Or "simply copy the calibre library folder from the old to the new computer", install calibre there, and point it at the copied folder with Switch/create library. Copy the whole folder, not just the books, so metadata.db comes with them.
The FAQ says the most important thing to back up is the library folder, with all its files and sub-folders. Time Machine or a copy to an external drive both work; close calibre while copying, so metadata.db is not mid-write. To keep your settings and plugins too, back up calibre's configuration folder as well (below).
The library has probably moved, or calibre is pointing at a different one. Use Switch/create library, or search for metadata.db to find where it went. If metadata.db itself is damaged, the FAQ's answer is Library maintenance > Restore database (right-click the calibre toolbar button), which rebuilds the database from the per-book backups. Try it on a copy of the folder first.
Preferences and plugins are separate from the library. On a Mac, calibre's source code puts its configuration folder here, unless the CALIBRE_CONFIG_DIRECTORY environment variable points elsewhere:
~/Library/Preferences/calibreThe FAQ says you can open it from Preferences > Miscellaneous. Homebrew's uninstall list for calibre also names ~/Library/Caches/calibre. Removing those resets calibre's settings but does not touch your books.
Libraries grow with every added format and cover. See the size with:
du -sh ~/Calibre\ LibraryRemove books inside calibre, not in Finder, so the database stays in step; they wait in .caltrash until it is emptied.
The e-books are in plain folders, so Spotlight can find them, but they sit in Author/Title (123) folders, and the files of a book added from elsewhere may carry names you never chose.
Type metadata.db into Everywhere to see where each library's database sits, including one on an external drive you have unplugged, or .epub to list every e-book file. Calibre names book files Title - Author, so part of a title is usually enough. A library in your home folder needs no extra permission, while one in Documents or on an external drive is covered once Everywhere has Full Disk Access. It matches file names only, not the text of a book.
Calibre suggests ~/Calibre Library on first run. To see the one you actually use, open Switch/create library from the library button in calibre's toolbar, or search for metadata.db.
In Switch/create library, enter an empty folder as the new location and choose Move the current library to new location. Calibre moves the files and updates its setting for you.
No. The calibre FAQ says it manages the folder structure itself and may delete files you add by hand. Rename or reorganise books inside calibre instead.
Use Export/import all calibre data from the calibre toolbar button's right-click menu, or copy the whole library folder to the new Mac and choose it with Switch/create library.
Everywhere keeps track of every file on your Mac — including the folders Spotlight hides and drives you have unplugged. Free for a day, then $19 once.
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