All of the changes you make in Firefox, like your home page, what toolbars you use, extensions you have installed, saved passwords and your bookmarks, are all stored in a special folder, called a profile. Your profile folder is stored in a separate place from the Firefox program so that, if something ever goes wrong with Firefox, your information will still be there. It also means you can uninstall Firefox without losing your settings and you don't have to reinstall Firefox to clear your information or troubleshoot a problem.

Table of Contents

How do I find my profile?

Finding your profile without opening Firefox

Firefox stores your profile folder in this location on your computer, by default:
C:\Users\ \AppData\Roaming\Mozilla\Firefox\Profiles\
Windows hides the AppData folder by default but you can find your profile folder as follows:

1. From the Start Screen, click the Desktop tile. The Desktop view will open.
2. From the Desktop, hover in the lower right-hand corner to access the Charms.
3. Select the Search charm. The Search sidebar will open.
4. In the search box, type in:
   %APPDATA%\Mozilla\Firefox\Profiles\
   without pressing Enter. A list of profile folders will appear.
5. Click on the profile folder you wish to open (it will open in a window). If you only have one profile, its folder would have "default" in the name.

1. click the Finder icon in the dock. On the menu bar, click the Go menu, hold down the option or alt key and select Library . A window will open containing your Library folder.
2. Open the Application Support folder, then open the Firefox folder, and then the Profiles folder.
3. Your profile folder is within this folder. If you only have one profile, its folder would have "default" in the name.

1. (Ubuntu) Click the Places menu on the top right of the screen and select Home Folder . A File Browser window will appear.
2. Click the View menu and select Show Hidden Files if it isn't already checked.
3. Double click the folder marked .mozilla .
4. Double click the folder marked firefox . Your profile folder is within this folder. If you only have one profile, its folder would have "default" in the name.

What information is stored in my profile?

Note: This is not a complete list. Only important information is described.

• Bookmarks, Downloads and Browsing History: The places.sqlite file contains all your Firefox bookmarks and lists of all the files you"ve downloaded and websites you've visited. The bookmarkbackups folder stores bookmark backup files, which can be used to restore your bookmarks. The favicons.sqlite file contains all of the favicons for your Firefox bookmarks.For more information, see Bookmarks in Firefox and Restore bookmarks from backup or move them to another computer .
• Passwords: Your passwords are stored in the key4.db and logins.json files. For more information, see Password Manager - Remember, delete and edit logins and passwords in Firefox .
• Site specific preferences: The permissions.sqlite and content-prefs.sqlite files store many of your Firefox permissions (for instance, which sites are allowed to display popups) or zoom levels that are set on a site-by-site basis (see Font size and zoom - increase the size of web pages).
• search engines: The search.json.mozlz4 file stores user-installed search engines. For more information, see Add or remove a search engine in Firefox .
• personal dictionary: The persdict.dat file stores any custom words you have added to Firefox's dictionary. For more information, see How do I use the Firefox spell checker? .
• Autocomplete history: The formhistory.sqlite file remembers what you have searched for in the Firefox search bar and what information you’ve entered into forms on websites. For more information, see Control whether Firefox automatically fills in forms .
• Cookies: A cookie is a bit of information stored on your computer by a website you've visited. Usually this is something like your site preferences or login status. Cookies are all stored in the cookies.sqlite file.
• DOM storage: DOM Storage is designed to provide a larger, more secure, and easier-to-use alternative to storing information in cookies. Information is stored in the webappsstore.sqlite file for websites and in the chromeappsstore.sqlite for about:* pages.
• extensions: The extensions folder, if it exists, stores files for any extensions you have installed. To learn more about Firefox extensions and other add-ons, Find and install add-ons to add features to Firefox .
• Security certificate settings: The cert9.db file stores all your security certificate settings and any SSL certificates you have imported into Firefox.
• Security device settings: The pkcs11.txt file stores security module configuration.
• Download actions: The handlers.json file stores your preferences that tell Firefox what to do when it comes across a particular type of file. For example, these are the settings that tell Firefox to open a PDF file with Acrobat Reader when you click on it. For more information, see Change what Firefox does when you click on or download a file .
• stored session: The sessionstore.jsonlz4 file stores the currently open tabs and windows. For more information, see Restore previous session - Configure when Firefox shows your most recent tabs and windows .
• Toolbar customization: The xulstore.json file stores toolbar and window size/position settings. For more information, see Customize Firefox controls, buttons and toolbars .
• User preferences: The prefs.js file stores customized user preference settings, such as changes you make in Firefox Options Preferences dialogs. The optional user.js file, if one exists, will override any modified preferences.

Are multiple people using the computer? Problems with the browser, but reinstalling it is undesirable? The program says that your profile could not be loaded? In all these cases, there is only one way out - to create a new Firefox profile without deleting the old one.

Today we will tell you how to do it and give a couple of tips.

How to create and download a new Firefox profile

First you need to find the program's shortcut. It can be located on the desktop, in the taskbar, or in the start menu. Open the properties of the shortcut, switch to the "Shortcut" tab and pay attention to the "Object" field there.

Here you must insert a space after the quotes, and after it add -p -no-remote as shown in the screenshot:

Thanks to this, every time you start Firefox, the profile manager will begin to appear. From it you can create a new one, select and load an existing one, and delete a profile if it is not needed. This is how the manager looks like for the author of this text, who works with several Firefox profiles at once:

Your original profile that you've been working with all this time is called default. Most likely, unlike the picture above, you will only have him in the list of available profiles. Without deleting it, you can create another completely clean Firefox profile. The "Create" button is located to the left of the list of profiles.

Creation is very fast. In the first window you will be told the theory:

A profile is where all of your data, additions, and changes you made to the original Firefox are stored. These are bookmarks, passwords, plugins, extensions, changed options and much more.

In the second window, you will be prompted to give the profile a name and choose where it will be stored:

One can agree with what is proposed without changing anything here. The existing "default" profile and the created "Default User" will be isolated from each other. Then just click the "Finish" button and your clean new profile will be ready:

Highlight it and click the Launch Firefox button to download a clean version of the browser. In this case, all your data will remain untouched and will be in the “default” profile, which you can also open using the same shortcut by selecting it in the profile manager.

By the way, if necessary, nothing prevents you from opening both of these profiles at the same time. You will get two Firefox windows, but not simple, but independent of each other. Each with its own settings and data. As a result, running multiple Firefox profiles is not difficult at all:

Where are Firefox profiles located

In the previous section, we explained what to do if Firefox won't start and gives you an error message stating that the profile could not be loaded (missing, not available, not found). As you understand, in this case, you just need to create a new clean profile. However, the question immediately arises about the former, because your, possibly valuable data, remained there.

The folder with the old profile could somehow be completely erased. If the profile is deleted, this is a very bad option. However, the situation can be a little more optimistic: for example, only some files were damaged. The folder, in turn, could not be deleted, but renamed or moved. Hence the profile error.

You should find the directory where Firefox stores profiles. Open the browser (since we have a new clean profile, it should now at least start), click on the main menu, go to the "help" section, find the item "information for solving problems" there:

Clicking on it will open a new tab with various information about the browser, and at the bottom there will be a link button to the current profile folder:

After clicking on it, the explorer window will start, where all the information of your current profile will be displayed.

In order to see all available profiles, you need to go one level up to the Profiles folder (click on the button indicated by the arrow in the screenshot above). As a result, you will be taken to the directory where folders with Mozilla browser profiles are stored. Each folder here is a profile. We have seven of them, you are unlikely to have more than two:

The folders start with a random set of characters, but when the name ends, it's easy to identify them. The Default User is our blank profile (unless, of course, you chose a different name for it during the creation process in the previous section). But default, highlighted in the screenshot, is the original profile, in which something could be saved.

Transfer files between Firefox profiles

All profiles have the same files, by manually copying or moving them with a replacement, you can move your data from one profile to another. Perhaps the most important are three types of data.

• places.sqlite are your bookmarks. The history of visits is also stored here. Along with this file, you can also transfer favicons.sqlite - these are the icons of your bookmarks;
• logins.json and key3.db are the two most important files where Firefox saves your passwords. You just need to move them together. If you don't have any password saved, you won't see the logins.json file;
• sessionstore.jsonlz4 - your tabs when you last left the browser. A few more sessions can be stored in the sessionstore-backups folder (these are files with .jsonlz4 permission, the one you need should be renamed to sessionstore and replace the base file with it).

Actually, for clarity, here are some of the files listed above in one of our test profiles:

Having made these replacements, you have a chance not only to reanimate Firefox with a new profile, but also to transfer data from the old one to it. If you are an inexperienced user, we advise you to manually backup everything that you will move and replace somewhere. Well, quite obvious advice: be guided by the size. The larger places.sqlite and sessionstore.jsonlz4, the more of your bookmarks and tabs they store.

Firefox profiles and versions

The new Firefox profile can help you out in many situations. For example, when serious problems arose with the browser, but, and even more so, reinstallation is undesirable.

Another obvious use case for Firefox profiles is using them for different versions of the browser. Let's say you are a web developer or just an enthusiast who, in addition to the stable version of Firefox, uses outdated and, on the contrary, new test versions on the computer:

For each of them, you can and should make a separate profile. Using one for all is a bad idea. Firstly, the icons on the browser toolbars will be shuffled after the launch of the old versions with the Australis interface and the new ones with the Photon interface. But these are trifles. But, secondly, downgrading is not recommended by Mozilla itself.

For example, if one profile has already loaded with a fresh test version, it is not recommended to run it on an older one. Especially if this is not a pure test profile, but your main one. Twice recently, in versions 55 and 58, Mozilla warned that it was making some changes that could cause profile incompatibilities.

As a result, it is better to create a separate profile for each version. For the program, by the way, creates it automatically. The rest you can do yourself:

It's very fast. The only inconvenience: each time you open any version of Firefox, you will have to manually select the desired profile from the list of available ones. This can be fixed by inserting in the properties of each shortcut the name of the profile that it should run by default:

For example, we did this for the beta version of Firefox, whose profile we simply call beta. The name is inserted between -p and -no remote without the leading hyphen and quotes.

This concludes our material. After reading it, you can easily create multiple profiles for one version of Firefox, or provide each version of Mozilla's browser with its own independent profile:

All changes made in Firefox, such as the home page, the panels you use, the extensions you have installed, your bookmarks, and saved passwords, are stored in a special folder called a "profile". Your profile folder is kept separate from the Firefox executables, so if something goes wrong with Firefox, your information will always be saved. It also means that you can uninstall Firefox without losing your preferences, and that you don't have to reinstall Firefox to remove information or fix a problem.

How can I find my profile?

How to find a profile without starting Firefox

Firefox saves your profile folder on your computer, by default in this location:
C:\Users\ \AppData\Roaming\Mozilla\Firefox\Profiles\
Windows hides the AppData folder by default, but you can find your profile folder like this:

Click the icon Finder in the dock. In the menu bar, click on the Go menu, and while holding down the option or alt key, select Library . A window will open containing your Library folder.

1. Open the Application Support folder, in it open the Firefox folder, and in it the Profiles folder.
2. Your profile folder is inside this folder. If you only have one profile, its folder will be named "default".

1. (Ubuntu) Open the Go menu at the top left of the screen and select Home Folder. The File Browser window will appear.
2. Open the View menu and select Show hidden files if it is not already checked.
3. Double click on the .mozilla folder.
4. If you only have one profile, its folder will be named "default".

What information is stored in my profile?

Note: This is not a complete list. Only important information is provided.

• Bookmarks, downloads and browsing history: The places.sqlite file contains all of your Firefox bookmarks, lists of all the files you've downloaded, and all the websites you've visited. The bookmarkbackups folder stores bookmark backup files that can be used to restore bookmarks. The favicons.sqlite file contains all the favicons for your Firefox bookmarks. For more information, read the articles How to use bookmarks to remember and organize your favorite sites and Restore bookmarks from a backup or transfer them to another computer.
• Passwords: Your passwords are stored in key4.db and logins.json files. For more information, read the article Saved passwords - Remember, delete, edit passwords in Firefox.
• Site specific settings: The permissions.sqlite and content-prefs.sqlite files store a lot of Firefox permissions (such as which sites are allowed to open pop-ups) or zoom levels set on a per-site basis (read the article Font size and page zoom - increase the size of web pages).
• Search engines: The search.json.mozlz4 file contains the search engines installed by the user. Read Add or remove search engines in Firefox for more information.
• Personal Dictionary: The persdict.dat file contains all the extra words you added to the Firefox dictionary. For more information, read the article How do I check spelling in Firefox? .
• Autocomplete fields: The formhistory.sqlite file remembers what you searched for in the Firefox search bar and what information you entered into fields on websites. For more information, see the article Control autofill forms with your information in Firefox.
• Cookies: Cookies are small pieces of data stored on your computer by the websites you visit. Usually it's something like site settings or login status. All cookies are stored in the cookies.sqlite file.
• DOM storage: DOM storage aims to provide a larger, safer, and easier-to-use alternative to storing information in cookies. The information is stored in the webappsstore.sqlite file for websites and in the chromeappsstore.sqlite file for about:* pages.
• Extensions: The extensions folder, if it exists, holds the files for all the extensions you have installed. To learn more about Firefox extensions and other add-ons, see Find and install add-ons to add features to Firefox.
• Security certificate settings: The cert9.db file contains all your security certificate settings and any SSL certificates that you have imported into Firefox.
• Security device settings: The pkcs11.txt file stores the configuration of protection modules.
• Actions when uploading files: The handlers.json file contains your settings that tell Firefox what to do when it sees certain types of files. For example, these settings tell Firefox to open PDF files with Acrobat Reader when you click on them. For more information, see Change what Firefox does when you click or download a file.
• Saved session: The sessionstore.jsonlz4 file stores the currently open tabs and windows. For more information, see Restore a previous session - Setting when Firefox displays your most recent tabs and windows.
• Toolbar settings: The xulstore.json file stores toolbar settings and window positions/sizes. For more information read the article

What are profiles in Mozilla Firefox? This is a set of settings, user information. Firefox can be run with a specific profile, and then Firefox will have its own settings, plugins, external display, and more. It's almost like having Firefox installed and configured separately.

This way you can create profiles for different users or for one user, but for different tasks.

For example, I needed profiles:

1. for everyday work on the Internet - social networks, authorization on the necessary sites, necessary bookmarks, your own history of visiting;
2. for work - this is authorization, remembering authorization on specific sites. Authorization of other accounts in social networks and so on.
3. for mom 🙂 Link to classmates in bookmarks in the most prominent place and authorization with memorization on the same site 🙂

Application may vary.

So what exactly is stored in profiles:

• Bookmarks and browsing history
• Passwords
• Special site settings
• search engines
• Personal dictionary
• Autocomplete fields
• Cookies
• Security certificate settings
• File type management
• User styles

Also, for each profile, you can set your own design and add-ons installed in Firefox in the current profile will also be available only in this profile.

How to manage Firefox profiles?

To do this, you need to start Firefox with the parameter. You can do this, Start -> Run and then enter (before that, you will need to close all open Firefox windows, otherwise executing the following command will simply launch the browser, not the profile manager)

firefox.exe -ProfileManager

I just want to note that the checkboxes in the window affect the current launch of the browser. Work offline - means that the browser will work offline (with)CEP.

If you select any of the profiles and check the "Do not ask at startup" checkbox, then the next time you start the browser without specifying a profile, it will start with the selected profile. If you uncheck the box, then every time you start the browser, you will be prompted to select a personal profile. If you checked the “Do not ask at startup” checkbox, but after that you needed to change the profile loaded by default, then you will need to start the profile manager again, as described above, and set the necessary settings.

Where is the profile stored? In my Windows XP files are stored here. One profile - one folder, for example zwv9xv8q.lampdevru.

C:\Documents and Settings\username\Application Data\Mozilla\Firefox\Profiles

C:\Documents and Settings\username\Application Data\Mozilla\\Profiles

You can also open the profile folder by doing the following: select the menu item Help -> Troubleshooting Information or in a new tab in the address bar we write about: support, the page loads, we see the following

How to start Firefox with the right profile?

To do this, the executable file must be launched with the parameter -p profilename. For example, you can create a shortcut and write the following in the "Object" property

What is a profile?

Firefox stores all the information that a user generates while using the browser in a special folder called a profile. Data such as bookmarks, cookies, browsing history, browser settings and installed add-ons, remembered passwords are saved. When you first start Firefox, a profile is created with default settings.

Profile Folder Location

Depending on the operating system, the default profile folder is located in the following paths.
If you created this folder yourself through the profile manager and specified a path other than the suggested one, the profile folder may be located in a different location.

Windows 95, 98 and ME

C:\Windows\Application Data\Mozilla\Firefox\Profiles\ \C:\Windows\Profiles\ \Application Data\Mozilla\Firefox\Profiles\

Windows 2000, XP

Select "Start → Run";

Enter %APPDATA%;

Click OK. A Windows Explorer window will appear;

In the Windows Explorer window, select "Mozilla → Firefox → Profiles". Each subfolder in this folder is a profile on your computer.

C:\Documents and Settings\ \Application Data\Mozilla\Firefox\Profiles\

The "Application Data" folder is a hidden folder. To show hidden folders, open Windows Explorer and select: "Tools → Folder Options → View tab → Show hidden files and folders".

Windows Vista and Windows 7

Press the start button to open the menu;

Enter %APPDATA% in the "Start Search" field;

Click on the “Roaming” item that appears in the menu;

In the Windows Explorer window that opens, select "Mozilla → Firefox → Profiles". Each subfolder in this folder is a profile on your computer.

You can also directly navigate to this folder using the following path:

C:\Users\ \AppData\Roaming\Mozilla\Firefox\Profiles\

The "AppData" folder is a hidden folder. To show hidden folders, open Windows Explorer and select: Organize → Folder and search options → Folder options → View tab → Show hidden files and folders.

*nix

Profile folders are located in:

~/.mozilla/firefox/

The ".mozilla" folder is hidden by default.

MacOS X

Profile folders are located in one of the following folders:

~/Library/Mozilla/Firefox/Profiles/ /~/Library/Application Support/Firefox/Profiles/

The tilde character (~) refers to the current user's home directory. So ~/Library is /Macintosh HD/Users/ /Library. (In the Russian version, the path to this folder may look like /Macintosh HD/Users/<имя пользователя>/libraries)

Finding a Profile Folder

You can use the Open Profile Folder extension, which will open your profile folder if you use the corresponding menu item in the "Tools" section.

Create a profile

Files and folders in the profile

It is not recommended to edit these files directly. Instead, use the user interface. The exceptions are three files whose name starts with "user". They are meant to be edited by the user directly. For more information about files, please refer to the table below.

Folders

Folder	Firefox version	Description
bookmarkbackups	1.5 and up	The last 5 copies of the bookmark file. Updated daily.
Cache	Below 1.5	Cache of files downloaded from the Internet. Note: Only profiles in Firefox 1.5 and above? created in non-standard locations in Windows include the Cache folder. For information about the location of the cache, use the about:cache command.
offline cache	3.0 and above	Second disk cache for offline file storage. Note: Only profiles created in non-standard locations on Windows include the OfflineCache folder. For information about the location of the cache, use the about:cache command.
chrome		To store userChrome.css and userContent.css files
extensions		Installed add-ons.
microsummary-generators	2.0 and above	Generated microsummaries.
minidumps		For the error reporting tool.
preferences		Contains the existing-profile-defaults.js file.
search plugins	1.5 and up	User-installed search plugins.

Files

Name	Firefox version	Description
.autoreg		Temporary empty file signaling a change in installed extensions
.parentlock (Mac OS X)		See parent.lock
blocklist.xml	2.0 and above	Automatically loaded list of dangerous extensions
bookmarks.bak	Below 3.0	Backup copy of the bookmarks.html file
bookmarks.html	Below 3.0	Bookmarks (menu Bookmarks → Manage bookmarks)
bookmarks.html.moztmp	Below 3.0	Temporary bookmark file. If you find it, remove the read-only attribute from it, as this results in a lot of bookmark files with names like bookmarks-n.html (Bug 157152)
bookmarks.postplaces.html	3.0 (prerelease)	Bookmark file backup in 3.0 Beta 4 and below and 3.0 nightly builds up to 3/14/2008. Not used in later 3.0 builds
bookmarks-(date).html in bookmarkbackups folder	Below 3.0
bookmarks-(date).json in bookmarkbackups folder	3.0 and above	Daily copy of the bookmark file
cert8.db		Security certificates (menu Tools → Options → Advanced → Encryption → View certificates). If you have problems with certificates, delete this files. See also key3.db and secmod.db
cert_override.txt	3.0 and above	Stores certificate exceptions specified by the user
compatibility.ini		Stores the version and path of the last application this profile was used with. When loading a profile with an application that has a different version or path, the XPCOM component registration process starts. This file can be deleted manually - it will be created automatically when you download the application
components.ini	Below 1.5	It lists extension folders that have XPCOM components. Replaced by extensions.ini in 1.5
compreg.dat		List of registered XPCOM components. Automatically regenerated when starting the XPCOM registration process
content-prefs.sqlite	3.0 and above	Page customization
cookies.sqlite	3.0 and above
cookies.txt	Below 3.0	Contains all your saved cookies (menu Tools → Options → Privacy → Show Cookies). Deleting this file will delete all your cookies
cookies.txt.moztmp	Below 3.0	Temporary cookie. If you find it, either remove it or remove the read-only attribute from it, as this will create a lot of files with names like cookies-n.txt (Bug 257288)
defaults.ini	Below 1.5	It lists extension folders containing files with default values. Replaced by extensions.ini in 1.5
downloads.rdf	Below 3.0	Download manager database. Contains a list of all uploaded files. May be removed to resolve issues with slow file uploads or Firefox freezing (Bug 159107)
downloads.sqlite	3.0 and above	Download manager database. Contains a list of all uploaded files
existing-profile-defaults.js in preferences folder	2.0.0.2 and higher	Overrides default Firefox settings. This file was used to prevent the default settings for existing profiles from being changed when the default search plugin was changed from Yahoo! on Google in Firefox 2.0.0.2 in Japan, China, Korea and Taiwan. Can be removed to restore the latest default settings
extensions.cache		Cache of installed extensions. It lists the installed extensions, their IDs and the folders they are installed into, as well as the date they were last modified. It is used, for example, to register extensions installed by copying to a folder, which is one of the extension installation locations recognized by Firefox. This file is regenerated automatically and can be deleted in case of problems with extensions
extensions.ini	1.5 and up	List of folders with installed extensions and themes. The file is generated automatically by nsExtensionManager and is used by low-level code to determine the chrome packages and XPCOM components provided by installed extensions. This file can be removed in case of problems with extensions
extensions.rdf		Information about installed extensions. This one can be removed in case of ghost extensions, as well as in case of problems with extensions
extensions-startup.manifest	alpha 1.5	Cache of installed extensions. This file was used in the Deer Park alphas and was later renamed to extensions.cache
formhistory.dat	Below 3.0
formhistory.sqlite	3.0 and above	Contains a database of saved form data
history.dat	Below 3.0	Browsing log: contains a database of all visited web pages (Browsing log menu). This file can be removed in case of problems.
hostperm.1	Below 3.0	Contains a list of sites that are allowed or denied to set cookies and that are allowed to open pop-up windows
key3.db		Key database for certificates (menu Tools → Options → Advanced → Encryption → View certificates). If you have problems with certificates, delete this file. When loaded, it will be recreated with default settings. Existing certificates will be removed and must be reinstalled
kf.txt	2.0	Database of keys for the operation of the anti-fraud mechanism (phishing)
localstore.rdf		Stores the location and size of windows and toolbars defined by the user. If you have problems with windows, delete this file
localstore-safe.rdf	1.5 and up	A special version of localstore.rdf used in safe mode to set window and toolbar settings to default
lock (Linux)		See parent.lock
mimeTypes.rdf		Specifies the actions to be taken when certain types of files are loaded. Can be removed to reset settings when uploading files to their defaults
parent.lock (Windows)		Created when Firefox starts with this profile and indicates that the profile is in use. Can be removed to unlock profile
permissions.sqlite	3.0 and above	Database with permissions to set cookies, open pop-ups, download images and install add-ons
persdict.dat		Personal Spelling Dictionary
places.sqlite	3.0 and above	Bookmarks and History
places.sqlite-journal	3.0 and above	Temporary storage for updates to the places.sqlite file when Firefox is open
pluginreg.dat	3.0 and above	Registering MIME types for installed plugins. Previously located in the Firefox folder containing profiles
prefs.js		All Firefox settings (see about:config)
search.rdf	Below 2.0
search.sqlite	2.0 and above	Information about your search plugins
secmod.db		Database of security devices (menu Tools → Options → Advanced → Encryption → Security devices)
sessionstore.js	2.0 and above	Saved Sessions
signons.txt	Below 1.5.0.10, Below 2.0.0.2 for 2.x branch	Encrypted saved passwords (menu Tools → Options → Security → Show passwords). Requires key3.db file to work
signs2.txt	Above 1.5.0.10 for branch 1.5.x, Above 2.0.0.2
signs3.txt	3.0 and above	Encrypted saved passwords (and exceptions for sites that have "Never save password" selected) (menu Tools → Options → Security → Show passwords). Requires key3.db file to work
signons.sqlite	3.5 and above	Encrypted saved passwords (and exceptions for sites that have "Never save password" selected) (menu Tools → Options → Security → Show passwords). Requires key3.db file to work
urlclassifier.sqlite or urlclassifier2.sqlite or urlclassifier3.sqlite	2.0 and above	Anti-Phishing Data File
urlclassifierkey3.txt	3.0 and above	Anti-Phishing Key Database
user.js (does not exist by default)		User defined configuration file. The values ​​from this file will be overwritten in the pref.js file when Firefox starts. The main difference between the user.js file and pref.js is that Firefox cannot change the values ​​set in user.js - only the user can do this
userChrome.css in chrome folder (doesn't exist by default)		User-defined CSS rules for changing the appearance of an application.
userContent.css in chrome folder (doesn't exist by default)		User defined CSS rules designed to change the appearance of web pages
userChrome.js in chrome folder (doesn't exist by default)		User-defined JavaScript code to change how the application works
webappsstore.sqlite	2.0 and above	DOM storage
xpti.dat		List of registered XPCOM interfaces. Automatically re-generated when starting the XPCOM registration process
XUL .mfasl (Linux)		See XUL .mfl
XUL .mfl (Windows)	Below 1.5	Cached user interface data. May be removed to resolve issues. Note: In Firefox 1.5 and higher, only profiles created in non-standard locations on Windows include a XUL .mfl file. For information about the location of the file, use the command about:cache
XUL FastLoad File (Mac OS X)		See XUL .mfl

Files and folders outside the profile

Name	Firefox version	Description
crash reports	3.0 and above	Crash files for Breakpad
Desktop Background.bmp (Windows)	1.5 and up	Desktop background image set by Firefox. The file is created when you select the "Set as desktop background..." item in the context menu.
pluginreg.dat	Below 3.0	Registering MIME types for installed plugins. In 3.0 pluginreg.dat is located in the profile folder.
profiles.ini		Contains profile location information. Can be edited to refer to a moved profile. If this file is deleted, then the next time you start the program, it will be regenerated along with a new default profile.
registry.dat		Contains information about the location of the profile in older versions of Firefox (no longer used).