Data models and storage formats

Files Firefox creates inside a profile, plus the on-disk schemas used by built-in features.

SQLite databases (in the profile)

File	Schema source	Contents
places.sqlite	toolkit/components/places/Database.cpp	Bookmarks + history
cookies.sqlite	netwerk/cookie/	Cookies
permissions.sqlite	extensions/permissions/	Per-origin permissions
content-prefs.sqlite	toolkit/components/contentprefs/	Per-page prefs (zoom, etc.)
webappsstore.sqlite (legacy)	dom/storage/	Old localStorage
formhistory.sqlite	toolkit/components/satchel/	Form history
favicons.sqlite	toolkit/components/places/	Favicon cache
places.sqlite-wal etc.	SQLite	Write-ahead logs

JSON files in the profile

File	Source	Contents
prefs.js	libpref	User-modified prefs
user.js	libpref	User overrides loaded before profile prefs
addons.json	AddonManager	Installed extensions
extensions.json	AddonManager	Extension state
extension-preferences.json	WebExtensions	Extension prefs
sessionstore.jsonlz4	Session Store	Tabs/windows for restore
containers.json	ContextualIdentity service	Container Tabs config
handlers.json	toolkit handlers	Protocol handlers
times.json	toolkit	Profile creation/usage timestamps

Quota-managed storage

<profile>/storage/{default,permanent,temporary}/<origin>/... — IndexedDB, Cache API, OPFS data, partitioned per origin.

Cache

<profile>/cache2/ — HTTP cache (binary index index + content-addressable files in entries/). Format documented in netwerk/cache2/.

Glean ping store

<profile>/datareporting/glean/ — Glean's local storage for pings and metrics, prior to upload.

MAR format (updates)

Mozilla ARchive: a custom format for binary patches, with built-in signature verification. Documented under docs/update-infrastructure/.

Related

• Storage
• Networking
• Update system