Where apps hide your files

Where macOS stores downloaded and custom dictionaries

Updated 2026-10-28 · 6 min read

Apple's downloaded dictionaries live in a protected folder under /System/Library/AssetsV2, and custom ones go in ~/Library/Dictionaries. Here is which is which, what you can and cannot change, and how to add your own.

The locations

The Dictionary app does not keep its dictionaries in your home folder. On macOS 15 Sequoia, the ones Apple lets you download are here:

/System/Library/AssetsV2/com_apple_MobileAsset_DictionaryServices_dictionaryOSX/

Each downloaded dictionary sits in a folder named with a long hexadecimal hash and ending in .asset, and the dictionary itself is in an AssetData folder inside it:

.../com_apple_MobileAsset_DictionaryServices_dictionaryOSX/<hash>.asset/AssetData/Oxford Dictionary of English.dictionary

On the Mac used for this guide, three are installed: Apple Dictionary.dictionary (about 41 MB), Oxford Dictionary of English.dictionary (about 37 MB) and Oxford Thesaurus of English.dictionary (about 7 MB). A .dictionary is a bundle, so Finder shows it as one item. Treat the hash as a wildcard, since it is not a name you can predict, and other macOS releases may use a different folder, so use the search tip below if yours differs.

Custom or third-party dictionaries go in a different pair of folders:

~/Library/Dictionaries
/Library/Dictionaries

The first is for you, the second for every user of the Mac. Neither existed on the Mac used for this guide, because nothing had been installed there; you create the one you need.

Why you cannot edit the Apple ones

The downloaded .asset folders are owned by a system account (_nsurlsessiond on the Mac used for this guide) and carry the restricted flag that System Integrity Protection enforces, so Finder and Terminal will not let you move, rename or delete things there, even with sudo. That is intentional. macOS fetches and updates these files itself. Looking is fine:

ls /System/Library/AssetsV2/com_apple_MobileAsset_DictionaryServices_dictionaryOSX

Next to the .asset folders sits an XML catalogue file of about 850 KB with the same name as the parent folder plus .xml, which is Apple's list of what is available for download. It is not something to edit. Apple does not document a way to remove a downloaded dictionary, so this guide does not give one.

Choosing and downloading dictionaries

The place to manage them is the app itself. Open Dictionary, choose Dictionary > Settings (the menu says Preferences on older macOS), and tick the sources you want. Apple's guide says the sources you select there decide which appear in Dictionary and which are used for lookups. Drag them into the order you prefer. The pane's own text asks you to "Drag reference sources into the order you prefer".

Ticking one you have not downloaded makes the app say it "needs to download some dictionaries before use", then show progress. Once the download is complete, a new .asset folder should appear in the folder above. The app's own message says quitting Dictionary will not interrupt downloads.

Wikipedia is different: it is a built-in online source, not a download. Its definition lives inside the system frameworks, in /System/Library/Frameworks/CoreServices.framework/Frameworks/DictionaryServices.framework/Resources/Wikipedia.wikipediadictionary, and the app reports an error if Wikipedia's server is unavailable.

Adding your own dictionary

You need a .dictionary bundle, which means one built for the Mac's Dictionary format; a plain word list or a spreadsheet will not work. The tool Apple provided for building one is the Dictionary Development Kit, which has shipped in the Additional Tools for Xcode download for registered developers; it is old and no longer updated, and it is not installed with Xcode itself. With a bundle in hand:

1. Quit Dictionary.
2. Create ~/Library/Dictionaries if it is missing (mkdir -p ~/Library/Dictionaries) and put the bundle in it.
3. Open Dictionary and go to Dictionary > Settings. The new dictionary should appear in the list for ticking.

The app also has an Open Dictionaries Folder command, which its menu resources place in the File menu; it should open ~/Library/Dictionaries in Finder, the quickest way to check you used the right folder. If nothing appears after you reopen Dictionary, check that the bundle is a genuine .dictionary and that it was built for macOS rather than for another system.

Your own words are not here

Words you teach the Mac are not stored in any of these dictionaries. They belong to the spelling checker, which keeps its own files in ~/Library/Spelling. The related guide on the spelling dictionary covers that folder, and this one covers the reference books.

What the app remembers

Dictionary is a sandboxed app, so its preferences file is inside its container: ~/Library/Containers/com.apple.Dictionary/Data/Library/Preferences/com.apple.Dictionary.plist, about 5 KB on the Mac used for this guide. Its key names point to window settings and a list of the dictionaries the app last found available. Do not edit it by hand: quit the app and use the Settings pane. A second small file, ~/Library/Preferences/com.apple.DictionaryServices.plist, is only 71 bytes there and not a place to edit either.

Moving to a new Mac

Apple's downloaded dictionaries are not something to copy. On the new Mac, open Dictionary, choose Settings and tick the ones you want, and macOS downloads them again. Only custom dictionaries need moving: copy the bundles in ~/Library/Dictionaries across, and the order you set in Settings has to be set again. Time Machine covers ~/Library/Dictionaries.

Why searches miss them

The Apple dictionaries sit under /System, which Finder and Spotlight searches leave out, in folders with hash names and a .dictionary bundle that looks like a single file, so a normal search for "Oxford" turns up nothing helpful.

Finding them again

Typing .dictionary into Everywhere lists every dictionary bundle on the Mac, Apple's under AssetsV2 and your own in ~/Library/Dictionaries, each with its full path, so you can tell which is which at a glance. Typing Oxford narrows it to the Oxford titles. Everywhere's scan covers /System/Library without any special permission, but new files added there can wait for the next scan; the preferences file inside Dictionary's container shows up only once it has Full Disk Access. It matches names only, never the definitions inside a dictionary.

Common questions

Where does a Mac store its dictionaries?

Downloaded Apple dictionaries are in /System/Library/AssetsV2/com_apple_MobileAsset_DictionaryServices_dictionaryOSX/, inside .asset folders with hash names. Your own go in ~/Library/Dictionaries, or /Library/Dictionaries for every user.

How do I add a custom dictionary to the Dictionary app?

Quit Dictionary, put a Mac-format .dictionary bundle in ~/Library/Dictionaries, then open Dictionary > Settings and tick it. A plain word list will not work.

How do I download more dictionaries on a Mac?

Open the Dictionary app, choose Dictionary > Settings, and tick the sources you want. The app downloads any it does not have yet, and quitting it does not interrupt the download.

Can I delete the downloaded Apple dictionaries?

Not by hand. The folder is protected by System Integrity Protection, and Apple does not document a removal method. Manage which are used from Dictionary > Settings.