None of these files should be read-only. If they are that might be a side effect of dragging and dropping or backing up files to removable media, and then using them to restore your profile.
| Name
| Description
|
| .autoreg
| Temporary empty file that signals a change in the installed extensions.
|
| .parentlock (Mac OS X)
| See parent.lock
|
| abook.mab
| Personal Address Book
|
| blocklist.xml
| Added list of dangerous extensions.
|
| cert8.db
| Security certificates
|
| compatibility.ini
| Stores version and path of the application this profile was last used with. When the profile is loaded with an application of a different version/path, the XPCOM components registration process is triggered. This file is automatically generated and can safely be deleted.
|
| components.ini
| Lists extension folders with XPCOM components. Replaced with extensions.ini in Thunderbird 1.5 and above.
|
| compreg.dat
| Lists registered XPCOM components. Automatically regenerated whenever XPCOM registration process is triggered.
|
| cookies.txt
| Cookies RSS cookies - Thunderbird
|
| cookies.sqlite
| Cookies used by Lightning extension
|
| downloads.rdf
| Download history. Can be deleted to resolve slow downloads or program hangs (Bug 159107)
|
| extensions.cache
| Lists installed extensions, their IDs, and the folders they are installed to, along with their last-modify time. It is used, for example, to register extensions installed by dropping a folder into one of known install locations. This file is automatically regenerated and can be deleted to resolve various issues.
|
| extensions.ini
| Lists folders of installed extensions and themes. The file is automatically generated by nsExtensionManager and is used by low-level code to detect chrome packages and XPCOM components provided by installed addons. It can be deleted to resolve various issues.
|
| extensions.rdf
| Installed extension information. It can be deleted to remove "ghost" entries from the extension list [1] and to resolve various other issues.
|
| filterlog.html
| Message filter log. If filter logging is enabled its stored in the accounts directory.
|
| history.mab
| Collected addresses
|
| hostinfo.dat in News
| Contains all the newsgroups available for the current server
|
| junklog.html
| Junk mail log for that account
|
| key3.db
| Key database
|
| localstore.rdf
| Toolbar and window layout and size/position settings. It can be deleted to resolve various issues.
|
| localstore-safe.rdf
| Special version of localstore.rdf used in Safe Mode to set toolbars and window customizations to defaults. [2]
|
| lock (Linux)
| See parent.lock
|
| mailviews.dat
| Defines your current message view (you can customize it)
|
| menuedit.rdf
| Used by MenuEdit extension
|
| mimeTypes.rdf
| Action to perform when downloading certain types of files. Can be deleted to reset download actions.
|
| msgFilterRules.dat in ImapMail, Mail, News
| Message filters
|
| nsmail.eml, nsmail.tmp, nsmail.html
| Temporary files created when sending a message.
|
| nstmp
| Thunderbird creates a nstmp temporary file when compacting a folder. You should not see it (or nstmp-1, nstmp-2 etc.) unless Thunderbird was interrupted while compacting.
|
| panacea.dat
| Mail folder cache
|
| parent.lock (Windows)
| Marker showing that the current profile is in use. Can be deleted to unlock the profile.
|
| persdict.dat
| Personal spelling dictionary
|
| permissions.sqlite
| Used by Lightning extension
|
| popstate.dat in Mail
| Keeps track of which messages have been left on the POP3 server
|
| prefs.js
| All preferences, including account settings and mail folder locations. See: Modify Thunderbird settings
|
| rulesbackup.dat
| If msgFilterRules.dat can't be read it backs it up in that file and creates a new msgFilterRules.dat.
|
| secmod.db
| Security module database
|
| signons.txt
| Encrypted saved passwords, requires key3.db to work
|
| storage.sdb
| Internal calendar data (in SQLite format) if you use the Lightning extension
|
| training.dat
| Custom training for Junk Mail Controls
|
| tmprules.dat
| Temporary file used when modifying message filters.
|
user.js
(does not exist by default)
| User-set overriding preferences
|
userChrome.css in chrome
(does not exist by default)
| User-set CSS to change the way the application looks
|
userContent.css in chrome
(does not exist by default)
| User-set CSS to change the way webpages look
|
userChrome.js in chrome
(does not exist by default)
| User-set JavaScript to change the way the application works
|
| virtualfolders.dat
| Saved Search folder settings
|
| xpti.dat
| Lists registered XPCOM interfaces. Automatically regenerated whenever XPCOM registration process is triggered.
|
| XPC.mfl
| A cache file for components (XPC)
|
| xul.mfasl (Linux)
| See XUL.mfl file
|
| XUL.mfl (Windows)
| Cached user interface data. Can be deleted to resolve various issues.
File location changed in Thunderbird 1.5. [3]
|
| XUL FastLoad File (Mac OS X)
| See XUL.mfl
|
| Name
| Description
|
| (number).s
| Obsolete. It used to be used for saving passwords. The "(number).s" value was specified by the signon.SignonFileName preference.
|
| * in ImapMail, Mail, and News (no file extension)
| Mbox files. They are text files that contain all of the messages for that folder.
|
| *.mab other than abook.mab and history.mab
| User-created or imported address books.
|
| *.msf in ImapMail, Mail, and News
| Index files for mail messages.
|
| *.mozeml
| Each file is a partial copy (up to 20kb) of a message in the mail folder, stored in a .mozmsgs subdirectory. Used by the optional Spotlight Integration component under OSX. It's deleted when the message in the mbox is deleted. [4]
|
| *.rc in News
| Subscribed groups.
|
