This document explains all of the optionspreferences available in the OptionsPreferences window of Mozilla Firefox.
When you open Firefox, by default your home page is displayed. Your home page might be a commonly-visited web site, a search engine, or perhaps your email account, but the choice is up to you. You can change your home page or choose to display a different page or set of pages on startup in this section.
When Firefox starts
By default, when Firefox starts it opens your home page (listed in the textbox immediately below), which corresponds to the Show my home page option. Alternately, you can choose to display a blank page on startup (perhaps to eliminate the time required to load that page from the Internet) by selecting the Show a blank page option.
As a final alternative, you can have Firefox reopen the windows and tabs you had open the last time you ran Firefox, effectively restoring you to where you were when you last stopped browsing the Internet. This can be a handy way of saving what you were doing when you close Firefox, perhaps to install an operating system update. You can choose this option by selecting Show my windows and tabs from last time.
Home Page
If you've set Firefox to show your home page when you start Firefox, you specify your home page by typing it here. You can also click any of the buttons below the textbox to choose a special home page:
This section contains optionspreferences determining how Firefox downloads files.
Show the Downloads window when downloading a file
With this optionpreference selected, Firefox will open the Downloads window when you start downloading a file.
Close it when all downloads are finished
Select this optionpreference to have Firefox close the Downloads window when all downloads currently in progress finish.
Save files to
By default downloaded files are automatically saved to the Desktop, eliminating the hassle of specifying a download location for every file you download. You can choose a different folder by clicking the button.
Always ask me where to save files
With this optionpreference selected, Firefox will ask you where you would like to save every downloaded file (instead of using the default location specified above).
Always check to see if Firefox is the default browser on startup
Select this option if you want Firefox to check whether it is the default browser at startup. This will ensure Firefox is used whenever an application tries to display a web page. You can also click the button to do a check right now.
Manage Add-ons
To install or uninstall, update or configure add-ons, click the button to open the Add-ons manager. This is also accessible from . A detailed description of add-ons and the Add-on manager is available here.
New pages should be opened in:
This optionpreference controls whether links from other applications or from web pages which request to open them in new windows are opened in a new window or a new tab in the most recent window.
Note: If you have chosen to open pages in new tabs, Firefox will ignore this optionpreference and will open a new window from a link if the page author specified that the new window should have a specific size, because some pages can only be displayed correctly at a specific size.
Warn me when closing multiple tabs
When you close a window with multiple tabs, Firefox will ask you to confirm your choice. This prevents you from accidentally closing the whole window when you intended to only close the current tab. Uncheck this optionpreference to disable this warning and have Firefox automatically close the window.
Warn me when opening multiple tabs might slow down Firefox
When you open a large number of tabs at once, Firefox will ask you to confirm your choice. This prevents you from accidentally slowing down your system while the pages are loading. Uncheck this optionpreference to disable this warning.
Always show the tab bar
If you're only viewing one web page in a Firefox window, the tab bar is not normally shown. Check this optionpreference to always show the tab bar, including when only the Firefox window contains only one page.
When I open a link in a new tab, switch to it immediately
When you middle-click on a Web link (or hold down CtrlCmd while clicking with the left mouse button), the page will be opened in a new tab. That page will not be displayed and will load in a background tab. Check this optionpreference to load and display the page in a new foreground tab instead.
Block Pop-up Windows
By default, Firefox blocks annoying pop-up windows on web sites. Unchecking this optionpreference will disable pop-up blocking.
Some web sites make legitimate use of pop-up windows. Therefore, you can allow these sites to open pop-ups anyway. To do so, click Exceptions…, enter the site name, and click Allow. To remove a web site from the list, select it and then click Remove Site. To clear the list completely, click Remove All Sites.
Load images automatically
Firefox displays images in web pages by default. Uncheck this optionpreference to disable images in web pages.
If you enable loading images automatically, the button lets you select sites from which images will not automatically load. The button lets you specify web sites that you wish to load (or not load) regardless of the setting of this preference. In the exceptions list, enter the site from which you want to allow or block images and click Allow to allow images, or click Block to block the images.
Enable JavaScript
JavaScript is a scripting language commonly used to make web pages interactive. However, it also makes certain annoying behaviors much easier to perform. To disable JavaScript, uncheck this optionpreference. However, note that disabling JavaScript may cause some sites to not work properly. For more fine-grained control over what JavaScript can and cannot do, click Advanced….
Move or resize existing windows: Uncheck this optionpreference to disable moving and resizing windows using scripts.
Raise or lower windows: Uncheck this optionpreference to make sure scripts cannot raise (bring to the front) or lower (send to the back) windows.
Disable or replace context menus: Uncheck this optionpreference to prevent web pages from disabling or changing the Firefox context menu.
Hide the status bar: Uncheck this optionpreference to force the status bar to be displayed in pop-up windows.
Change status bar text: Uncheck this optionpreference to disable changes to status bar text (such as displaying scrolling text messages or preventing the link address from being displayed while the mouse is over a link).
Enable Java
Java is a popular programming language for the Web. A single Java program can run on many different kinds of computers, thus avoiding the need for programmers to create a separate version of a program for each kind of computer. Uncheck this optionpreference to disable Java applets in Firefox. Note that in order for Java applets to work, you must install the Java plugin.
Default font and Size
Web pages are usually displayed in the font and size specified here. However, web pages can override these choices unless you specify otherwise in the Fonts dialog. Click the button to access the Fonts dialog and to change this and other fonts optionspreferences.
Print
Edit this page
Translate this pageMonospace fonts.
You can also set the minimum web page font size. This is useful to prevent sites from use overly small fonts that are barely readable.
Allow pages to choose their own fonts, instead of my selections above
By default Firefox uses the fonts specified by the web page author. Disabling this optionpreference will force all sites to use your default fonts instead.
Character Encoding
The character encoding selected here will be used to display pages that do not specify which encoding to use.
Text and Background
Here you can change the default text and background color to be used on web pages that haven't specified that information. Click on the color samples to select colors.
Use system colors
Check this optionpreference to use the colors defined in your operating system settings instead of the colors specified above.
Link Colors
Here you can change the default colors for Web links. Click on the color samples to select colors.
Underline links
By default, links are underlined on web pages. Uncheck this optionpreference to disable this. Note that many sites specify their own styling rules and this optionpreference has no effect on those sites.
Allow pages to choose their own colors, instead of my selections above
By default, Firefox uses the colors specified by the web page author. Disabling this optionpreference will force all sites to use your default colors instead.
The Download Actions dialog, which can be opened by clicking the button, contains file types that you have downloaded. You can choose what Firefox should do when clicking on a specific file type by selecting the file type you want to modify and clicking the button.
This will display the Change Action dialog, where you can choose to have the file type opened by the default application, opened by a particular application, saved to disk, or shown with an installed plugin. For example, if you view lots of media files on web pages, you might want to specify that Firefox always open media files in your media player instead of asking where you want each media file to be saved.
Some web pages are offered in more than one language. Click the button to specify your preferred language or languages.
Languages Dialog
To add a language, click Select a language to add…, choose the language, and click the button. Remove a language by selecting it in the list of active languages and clicking the button. You can also reorder languages using the and buttons to determine the most preferred one in case a page is provided in multiple languages .
Feeds are specially formatted documents which summarize the content of web sites. For example, a feed might summarize the latest news headlines from a news site or the latest posts on a blog. You can view the content of feeds in Firefox, create Live Bookmarks for them, or add them to a feed reader on your computer or on the Web. The optionpreference in this pane determine what Firefox does when you view a feed.
Show me a preview and ask me which Feed Reader to use
When you view a feed within Firefox, you will be shown a preview of its contents. With this optionpreference selected, you are always given a choice of what you would like to use to subscribe to the feed at the top of the preview page.
Subscribe to the feed using
Instead of displaying a preview of the feed when you view one, you can have the feed be opened directly in a feed reader by selecting a reader from the list of available readers. You can choose to use an application on your computer to subscribe to feeds by clicking the button and finding the application on your computer. Alternately, you can choose to automatically subscribe to feeds by saving them as Live Bookmarks. To choose a subscription method, simply select it from the list.
The Applications panel lets you choose applications and other handlers to handle different types of content (e.g. PDF documents). It shows you a list of content types and lets you select a handler for each type.
You can choose a local application to handle any type. For some types, you can also choose a web application to handle the type, choose a feature (like Live Bookmarks for feeds) or a plugin in Firefox to handle the type, or save the type on your computer.
To choose a handler for a type, select the type from the list. The current handler for the type will turn into a menu. Open the menu and select the handler you want to handle the type.
Note: When a plugin is available to handle a type, and you choose another handler to handle that type, Firefox will only use your chosen handler when you access the type directly. When the type is embedded inside a web page, Firefox will continue to use the plugin to handle the type.
Remember visited pages for the last … days
Here you can specify how long you want Firefox to remember what pages you have visited. The default is 9 days.
Keep my history for at least … days
Here you can specify how long you want Firefox to remember what pages you have visited. The default is 90 days.
Remember what I enter in forms and the search bar
When you enter information in web forms or the search bar in Firefox, that information is saved so that Firefox can give suggestions when you enter information in forms in the future. To stop this behavior, uncheck this optionpreference.
Remember what I've downloaded
This optionpreference controls whether or not past downloads show up in the Downloads window. The Downloads window (accessible from or by pressing CtrlCmd+J CtrlCmd+Y) displays a list of your recent downloads. Downloads optionspreferences are available in the Main panel.
A cookie is a file created by a web site that stores information on your computer, such as site-specific preferences when visiting that site.
Accept cookies from sites
By default cookies are enabled. Uncheck this optionpreference to disable the use of cookies. Note that some sites may not work properly when cookies are disabled.
Accept third-party cookies
Unselecting this option will restrict cookie usage to the originating Web site only, meaning that no foreign cookies will be stored. To learn more about this, read about managing cookies.
Keep until:
To control which sites may or may not set cookies, click the button.
To display the Cookie Manager click Show Cookies….
Learn more about cookies, the individual optionspreferences, and how you can gain control over what sites are allowed to store cookies on your computer by reading about managing cookies.
Always clear my private data when I close Firefox
You can choose to have Firefox clear your private data when you close it. To configure what data is cleared, click the button.
Ask me before clearing private data
With this optionpreference selected, Firefox will ask you before before automatically clearing the data specified by clicking Settings….
If you wish to clear your private data right now, you can click the button to do so. To clear your private data from outside the preferences dialog, either press CtrlCmd+Shift+Del or select .
Warn me when sites try to install add-ons
Firefox will always ask you to confirm installations of add-ons. To prevent unrequested installation prompts which may lead to accidental installations, Firefox warns you when a web site tries to install an add-on and blocks the installation prompt. To allow installations from a specific site, click Exceptions…, enter the site name, and click Allow. Uncheck this optionpreference to disable the warning for all sites.
Tell me if the site I'm visiting is a suspected attack site
Check this optionpreference if you want Firefox to check whether the site you are visiting may be an attempt to interfere with normal computer functions or send personal data about you to unauthorized parties over the Internet.
Note that the absence of a warning does not guarantee that a site is trustworthy.
Tell me if the site I'm visiting is a suspected forgery
Check this optionpreference if you want Firefox to actively check whether the site you are visiting may be an attempt to mislead you into providing personal information (this is often referred to as phishing).
Note that the absence of a warning does not guarantee that a site is trustworthy. If you come across a "phishing" site which is not marked as such, please report it using , as explained in the menu reference.
Check using a downloaded list of suspected sites
With this optionpreference selected, Firefox will check the current site against a frequently updated list stored on your computer. No data about the sites you visit is transferred to third-party anti-phishing providers during normal browsing. Since phishing techniques and sites evolve quickly, this mode of protection may not be as effective as having an anti-phishing provider check every site you visit.
Check by asking … about each site I visit
With this optionpreference selected, Firefox will send the address of the current page over an encrypted connection to the selected third-party anti-phishing provider in order to verify its identity. This method offers the greatest protection, but information such as your IP address and browser version may be transfered and stored by the selected provider. You will be prompted to review and agree to the selected data provider's privacy policy after selecting this optionpreference.
Remember passwords for sites
Firefox can securely save passwords you enter in web forms to make it easier to log on to web sites. Clear this checkbox to prevent Firefox from remembering your passwords.
Even with this optionpreference checked, however, you'll still be asked whether to save passwords for a site when you first visit it. If you select Never for This Site, that site will be added to an exceptions list. To access that list or to remove sites from it, click the button.
Use a master password
Firefox can protect sensitive information such as saved passwords and certificates by encrypting them using a master password. If you create a master password, each time you start Firefox, it will ask you to enter the password the first time it needs to access a certificate or stored password. You can set, change, or remove the master password by checking or unchecking this optionpreference or by clicking the button. If a master password is already set, you will need to enter it in order to change or remove the master password.
Show Passwords…
You can manage saved passwords and delete individual passwords by clicking the button.
Saved Passwords…
You can manage saved passwords and delete individual passwords by clicking the button.
Click the button to configure the security warnings Firefox displays while you browse the web.
I am about to view an encrypted page: When this optionpreference is enabled, Firefox will notify you every time you are about to view an encrypted page.
I am about to view a page that uses low-grade encryption: With this optionpreference enabled, Firefox will warn you when you visit a page which uses low-grade encryption.
I leave an encrypted page for one that isn't encrypted: With this optionpreference enabled, Firefox will warn you every time you move from an encrypted page to an unencrypted page either by selecting a link on the page, selecting a bookmark or typing a new address into the location bar.
I submit information that's not encrypted: When this optionpreference is enabled, Firefox will warn you when you submit data via a form that's not encrypted.
I'm about to view an encrypted page that contains some unencrypted information: With this optionpreference enabled, Firefox will warn you when the page you're viewing contains a mixture of encrypted and unencrypted content. If an encrypted page contains unencrypted data, you should verify the identity of the page you're viewing prior to entering sensitive data.
The advanced panel contains many optionspreferences that are less likely to be used by most people but are useful and sometimes critical optionspreferences for some people.
Always use the cursor keys to navigate within pages
When this optionpreference is enabled, Firefox will display a movable cursor in web pages, allowing you to select text with the keyboard. You can toggle this mode by pressing F7.
Search for text when I start typing
When this optionpreference is enabled, Firefox will find within the current web page what you type as you type it. While you are finding typed text in the page, the Find Toolbar will automatically display at the bottom of the window to show information about what you've found.
Warn me when web sites try to redirect or reload the page
When this optionpreference is enabled, Firefox will prevent web sites from redirecting you to another page, or automatically reloading.
Use autoscrolling
Autoscrolling is a useful feature which allows you to scroll the page by clicking the middle mouse button (usually the scroll wheel) and moving the mouse up or down. Some people find this annoying, so autoscrolling can be disabled with this optionpreference.
Use smooth scrolling
Smooth scrolling can be very useful if you read a lot of long pages. Normally, when you press Page Down, the view jumps directly down one page. With smooth scrolling, it slides down smoothly, so you can see how much it scrolls. This makes it easier to resume reading from where you were before.
Check my spelling as I type
When this preference is enabled, Firefox will check your spelling and offer possible corrections as you type in web forms. Note that you may need to download a dictionary; to do so, right-clickpress Ctrl and click on any text field, enable spellchecking if necessary, and then use the provided menu to download a dictionary.
Some web pages are offered in more than one language. Click the button to specify your preferred language or languages.
Languages Dialog
To add a language, click Select a language to add…, choose the language, and click the button. Remove a language by selecting it in the list of active languages and clicking the button. You can also reorder languages using the and buttons to determine the most preferred one in case a page is provided in multiple languages .
Always check to see if Firefox is the default browser on startup
Select this option if you want Firefox to check whether it is the default browser at startup. This will ensure Firefox is used whenever an application tries to display a web page. You can also click the button to do a check right now.
Your organization or Internet service provider may offer or require you to use a proxy. A proxy acts as an intermediary between your computer and the Internet. It intercepts all requests to the Internet to see if it can fulfill the request using its cache. Proxies are used to improve performance, filter requests, and hide your computer from the Internet to improve security. Proxies are often part of corporate firewalls.
Use system proxy settings: This is the default preference. Choose this if you want to use operating system's proxy settings.
Use system proxy settings: This is the default optionpreference. Choose this if you want to use the proxy settings configured for you operating system.
Manual proxy configuration: Choose this if you don't have a proxy location (URL). Ask your system administrator for the names and port numbers of the servers running proxy software for each network service and enter the information in the appropriate fields.
Automatic proxy configuration URL: If your workplace has a proxy configuration file, ask the system administrator for its URL and enter it here. Click Reload to load the settings.
Pages you view are normally stored in a special cache folder for quicker viewing the next time you visit the same page. You can specify the amount of disk space the cache can use here. You can also immediately clear the contents of the cache.
Use up to … MB of space for the cache
Allows you to specify the maximum size, in megabytes, of the cache on your computer.
Clear Now
Immediately clears the current contents of the cache, freeing the disk space used by the cache.
Tell me when a website asks to store data for offline use
Allows websites to store data necessary to be used without an internet connection. If you have previously blocked a website from storing data for offline use and changed your mind, you can click the button. Select the site you want to stop blocking, and click . To remove all websites in the list, click .
The following websites have stored data for offline use:
After a website has stored data for offline use, you can select it in the list, and click to delete the data.
Firefox can check whether updates to installed add-ons or to Firefox itself are available.
Automatically check for updates to:
By default Firefox automatically checks for updates to itself, to add-ons, and to search engines so you'll always know you have the most up-to-date version. You can change this behavior by changing the appropriate checkboxes here.
When updates to Firefox are found,
Ask me what I want to do: Updates to Firefox are installed automatically by default. Select this optionpreference to manually control how and when updates are installed.
Automatically download and install the update: When this optionpreference is selected, Firefox updates will be automatically downloaded and will be installed the next time Firefox is restarted. The Warn me if this will disable any of my add-ons optionpreference determines whether you will be warned before the installation of an update which would require an incompatible add-on to be disabled because no newer, compatible version exists. The warning will allow you to postpone installation of the update, though at the expense of improvements included in it.
If all extensions and themes are compatible or can be updated to be compatible, the Firefox update will be installed. Upon restart you will be asked to install any needed add-on updates so that you can continue to use them.
Firefox automatically records the updates you have installed. You can view information about these updates by clicking this button.
Note: You must be running Firefox as an administratorroot or as the user who originally installed Firefox to install Firefox updates.
Use SSL 3.0
Specifies whether you want to send and receive secured information through SSL3 (Secure Sockets Layer, Level 3), a standard protocol for communicating securely with web sites. Disabling it will prevent you from visiting some sites.
Use TLS 1.0
Specifies whether you want to send and receive secured information through TLS (Transport Layer Security), a security standard similar to SSL3 (Secure Sockets Layer). Disabling it will prevent you from visiting some sites.
Certificates help perform encryption and decryption of connections to secure sites.
When a web site requires a certificate:
Some servers ask you to identify yourself with a personal certificate. In order to do so, they ask Firefox to generate one for you. When you visit the site in the future, Firefox selects the certificate without asking you by default. If you wish to manually choose a certificate (for example, if you have multiple certificates stored for multiple web sites), select the Ask me every time optionpreference and you'll be in complete control of what certificates are being sent to web sites while browsing.
When a server requests my personal certificate:
Some servers ask you to identify yourself with a personal certificate. In order to do so, they ask Firefox to generate one for you. When you visit the site in the future, Firefox selects the certificate without asking you by default. If you wish to manually choose a certificate (for example, if you have multiple certificates stored for multiple web sites), select the Ask me every time optionpreference and you'll be in complete control of what certificates are being sent to web sites while browsing.
Click this button to view stored certificates, import new certificates, and back up or delete old certificates in Firefox.
Firefox can use Certificate Revocation Lists (also known as CRLs) to ensure that your certificates are always valid. Click the Revocation Lists button to manage the CRLs installed on your computer.
Firefox may ask an OCSP (Online Certificate Status Protocol) server to confirm that a certificate is still valid. By default, Firefox validates a certificate if the certificate provides an OCSP server. Alternately, you can choose an OCSP server against which to validate all certificates. Click the button to manage these optionspreferences. You will most likely only need to change this if your Internet environment requires it.
Security devices can encrypt and decrypt connections and store certificates and passwords. If you need to use a security device other than the one in Firefox, click the button.
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