This article lists some extensions that are known to cause problems. There are hundreds of extensions, and most problems are not listed here. If you do not find the problem listed below, follow the steps outlined in the Standard diagnostic - Firefox article.

Extensions are not written by Mozilla and they are not tested with the browser or in combination with each other. Extensions are normally installed by visiting a website such as addons.mozilla.org and clicking an "Install" link but there are also many applications that include Firefox extensions or toolbars that can be installed without you being aware of it. [1], [2]

Updating extensions can solve many problems. Extensions installed as experimental do not get automatically updated. Extension versions needed after upgrading Firefox may be experimental or only available on the extension developer's site.

Most extensions can be disabled or uninstalled in Firefox using the Add-ons manager ("Tools -> Add-ons -> Extensions") although a few extensions may present removal problems. In some cases, you may need to run Firefox in a special mode called "Firefox Safe Mode" to access the Add-ons manager. You may also need to reset preference changes made by the extension that may persist after it is disabled or uninstalled. See Uninstalling add-ons and Uninstalling toolbars for more information.

Extension Extension version affected Problem Workaround References

Adblock All Having the OBJ_TABS setting enabled may interfere with the Java, Flash or Windows Media Player plugins. Content requiring these plugins may not display unless this setting is disabled. If updating to Adblock 0.5.3.042 or later does not resolve the issue, keep the Adblock OBJ_TABS setting disabled. [4][5] [6] [7]

Causes Google Gmail Chat to crash. ? [8]

Adblock Plus All ? Can interfere with Flash content, most often on Mac OS. Uncheck "Show Tabs on Flash and Java" in Adblock Plus options. [9] [10]

Causes excessive memory use and memory leaks. ? [11][12]

All-In-One Gestures All versions using Firefox 2? May cause Firefox crashes. Also conflicts reported with spellchecker in Linux Mac OSX versions. [15] [16]

All-In-One Sidebar 0.6.4 and prior New extensions will not install. Also occurs in version 0.6.4 if updated from an earlier version or if used together with the SessionSaver extension. Uninstall, then (re)install version 0.6.4. Disable opening the Extensions window in the sidebar (Misc. -> Extensions -> Open in Sidebar). [17] [18]

Amazing Media Browser 0.17 The "Block all embedded objects" preference is set to "Yes" by default, causing embedded media normally handled by plugins to disappear, including Flash content. Also interferes with the IE Tab extension. Change the "Block all embedded objects" preference setting to "No". [19][20]

AVG Safe Search



Installed with AVG Anti-Virus (LinkScanner component). 8.0 Blocks use of ENTER key from the location bar. Disable in Firefox "Tools -> Add-ons -> Extensions" or update to AVG 8.5 or above. [33] [34] [35]

DownThemAll 1.0 May cause web browsing to slow to a halt to the point that nothing loads.



Important: DownThemAll 1.0 changes certain "network.http" preferences that will need to be reset, even if you disable or uninstall the extension. Update to version 1.0.1 and reset these preferences via about:config: network.http.max-connections

network.http.max-connections-per-server

network.http.max-persistent-connections-per-proxy

network.http.max-persistent-connections-per-server [49] [50] [51][52]

All (?) since 1.0 May cause Windows error opening Internet shortcut or local HTML file - Firefox If updating DownThemAll to version 1.0.2 or later does not resolve the issue, disable or uninstall the extension. [53]

EBay Browser Highlighter ? Installs with Skype. Highlights things like products, phone numbers, important people. Causes Firefox to take up to 30 seconds to load. Disable or uninstall the extension. [54] [55] [56] dev-apps-firefox

eBay Hot Toolbar ? Highlighted text follows cursor as you move within a web page Disable or uninstall the extension. [57]

external IP Prior to 0.9.9.3 Causes Firefox crashes and authentication popups asking username/password for "Development Area" at http://www.crazzy.se Update to version 0.9.9.3 or above [58] [59]

Fast Dial 2.16 Adds "spam" links to the Bookmarks menu, adds the UserLogos search plugin and makes it the default search engine, searches may redirect. Update to version 2.18 or above (available from the Fast Dial Homepage). If necessary, delete unwanted bookmarks and change to your preferred search engine in the Firefox Search Bar. [60] [61] [62]

2.15 Conflicts with the IE Tab extension (broken/blank Location Bar) and the Tab Mix Plus extension (oversized tab bar) , adds "spam" links to the Bookmarks menu, adds the UserLogos search plugin and makes it the default search engine, searches may redirect. May interfere with toolbars from other extensions. Update to version 2.18 or above (available from the Fast Dial Homepage). If necessary, delete unwanted bookmarks, reset toolbar customizations and change to your preferred search engine in the Firefox Search Bar. [63] [64][65] [66]

All Changes made by Fasterfox can interfere with Web site access and persist after it is uninstalled. Reset options to defaults in Fasterfox before uninstalling it; otherwise, reset preferences in Firefox to the defaults (or create a new profile). [68]

Filterset.G Updater Prior to 0.3.0.2 Memory leak when used in conjunction with FlashGot Update to version 0.3.0.2. [69]

1.5.4 +? Downloaded files will be stored in memory, possibly causing high memory use. Disable Firebug when you don't need to use it [73][74][75]

Prior to 1.3.2 Firefox crashes on logout from Yahoo! Mail, reported in Firefox 2. Note: Firebug 1.3.2 (and above) requires Firefox 3. Disable Firebug when you don't need to use it. [76][77]

Firefox Google Bookmarks Prior to 0.2.1? Interferes with spell checking in Firefox version 2. Update to version 0.2.1. If that does not work, uninstall extension. [78]

FireFTP All? Can cause excessive CPU usage with Firefox 2.0.0.1 Update Firefox to the latest version [79]

FlashBlock All NoScript blocks JavaScript, which is required by FlashBlock Do not use both FlashBlock and NoScript together (NoScript includes Flash-blocking functionality) [80]

FlashGot Prior to 0.5.9.995 Memory leak when used in conjunction with Filterset.G Updater Update to FlashGot version 0.5.9.995 or later [81]

ForecastFox version 0.9.x and all satellite images versions? Memory leak Update or uninstall and install Forecastfox l10n. There are unconfirmed reports that there are also memory problems with versions 0.9.3 and 0.9.4. [82][83]

[84]

Prior to 0.9.5.1 Causes excessive CPU usage with Firefox 2.0 and Firefox 2.0.0.1 Update to Firefox 2.0.0.2 and ForecastFox 0.9.5.1 [85][86]

Free Download Manager

(Firefox extension) Prior to 1.3.4 The Free Download Manager application (FDM) installs an extension for Firefox integration which can cause Firefox crashes when right-clicking a Web page. Download and install the latest version (FDM 2.5 build 758 will update the extension to v 1.3.4) . Note: The FDM extension (v 1.0 - 1.3.1) is on the Add-ons Blocklist; v 1.3.2 is not blocklisted but it also crashes Firefox. [87] [88] [89]

? May cause notably increased disk usage (in gigabytes) by creating large log files. May cause periodic Firefox freezes. Uninstall [92][93]

3.1 New tab page option creates a thumbnail for each visit greatly increases size of places.sqlite Right click the Google logo in the Google toolbar > Options > Uncheck “Enable the Google new tab page” [98] [99] [100]

All

*Notice* Google Toolbar is not and will not be supported by Google for Firefox 5 and above see Using Google Toolbar features without toolbars for alternative solutions [[101]] [[102]]

Greasemonkey All Greasemonkey scripts do not work on sites blocked by NoScript Set NoScript to allow JavaScript on sites you wish to use Greasemonkey scripts on. [103]

All Causes excessive memory use and other performance problems. Disable when not needed.

Hebrew Calendar Prior to 1.0.4.36 Causes "ReferenceError: JEvent is not defined" Update to a newer version [104]

How Many Times Can I Back? All? Causes Unselectable/ Frozen tabs, breaks use of mouse to open and close tabs. Can still use "List all Tabs", Ctrl+T, and Ctrl+W. Disable extension. Problem caused by Firefox 29 updates relating to tabs. [105]

HP Smart Web Printing All? Interferes with menus. May interfere with printing if used with AdBlock. Disable, or use a JavaScript replacement. [106][107]

illimitux ? Can cause sessions to time out. Resets the network.http.sendRefererHeader preference. Uninstall illimitux and reset network.http.sendRefererHeader to the default value on the about:config page. [109]

iMacros Prior to 0.5.0.4 Causes excessive CPU usage Update to a newer version [110]

ImageTweak All versions ? Prevents closing first tab opened Uninstall or ? [111]

ImgLikeOpera 0.6.15 "Refresh images in tab on tab select" option causes excessive CPU usage on tab change and erratic text box behavior (i.e. losing caret after selection in google search text box). Turn off "Refresh images in tab on tab select" option. [112]

LiveHTTPHeaders All? Uploading a file locks the file so it cannot be renamed, moved, or deleted. Uninstall LiveHTTPHeaders. [114]

McAfee SiteAdvisor

Note:

This extension is on the Add-ons Blocklist. 3.3.1 and below Firefox crashes at startup. This can occur after updating Firefox, if add-on compatibility checking is turned off or if the extension erroneously marks itself as compatible. Start in Firefox Safe Mode and disable McAfee SiteAdvisor. If SiteAdvisor is a McAfee suite component it can also be removed using the McAfee uninstaller. [115] [116] [117]

3.3 After bookmarking a page with Bookmark Star can't Edit the bookmark from the Bookmark star nor with Ctrl+D to modify or remove the bookmark in at least Firefox 3.6.12 and 3.6.13. In Firefox beta 4.0b9pre though it doesn't interfere with bookmark star it hangs Google Search and so does not do its function of reporting on sites in search results listing. Uninstall or Disable the SiteAdvisor extension or, if SiteAdvisor is installed as part of a McAfee software suite, remove the SiteAdvisor component using the McAfee uninstaller. McAfee is rewriting code to prevent future delays [118] [119] [120] [121] [122] [123]

3.4.0 Messages like "Exc in ev handl: Error: Bad NPObject as private data!", "Exc in ev handl: This .0root.enable is not a function", "Exc in ev handl: TypeError: oSAPlg.oRoot.log is not a function". The reason for a lot of these problems is probably because 3.4 brought the extension out of the addons blocklist. Uninstall and reinstall is probably best to avoid future problems. (Windows): You must uninstall from Control Panel > add/change programs (Programs and Features). Reboot the system. Then Reinstall from http://www.siteadvisor.com/ and reboot the system. When installing refuse other suggested (crapware) applications. [124] [125] [126]

MegaUpload Toolbar All? Causes the error message, Trying to load a non-local URI. Also changes the user agent by adding "MEGAUPLOAD 1.0" which causes some websites to tell you to update to a modern browser. Uninstall the toolbar. To restore the user agent, type about:config in the Location Bar and filter for general.useragent. If the general.useragent.extra.firefox preference shows a user set status, right-click it and select Reset. [129] [130]

Menu Editor 1.2.4

(and 1.2.5?) Middle mouse button no longer opens new links from web pages Update to the latest version; if the issue persists, disable the extension [131] [132] [133]

Nightly Tester Tools All Allows incompatible extensions and themes to run; these incompatible add-ons can cause problems Update your extensions and themes to those compatible with your version of Firefox [135]

NoScript All Causes an illegal operation in the Windows Media Player plugin if it is blocking JavaScript on a page with embedded Windows Media Do not block websites that have embedded Windows Media if you want to be able to play the media [136] [137]

FlashBlock requires JavaScript to work to block flash ads Do not use both FlashBlock and NoScript together (NoScript includes Flash-blocking functionality) [138]

Greasemonkey scripts require JavaScript Set NoScript to allow JavaScript on sites you wish to use Greasemonkey scripts on. [139]

All since 1.1.9.5 Flash and other plugin content is blocked by default on untrusted sites, even content from trusted sites (e.g. YouTube.com) if embedded on an untrusted site. Uncheck the option to forbid Flash or other plugins in NoScript's Options\Plugins pane or temporarily allow the content by clicking on its placeholder. [140] [141] [142]

All since 1.1.0 Java is blocked by default on untrusted sites Uncheck "Forbid Java" in NoScript's Options\Plugins pane (Options\Advanced\Untrusted in earlier versions). In version 1.1.3 and later you can temporarily allow Java content by clicking on its placeholder. [143] [144]

Prior to 1.8.1.3 Cannot log into eBay or other sites with NoScript "Automatic Secure Cookie Management" enabled. Update NoScript to the latest version. [145]

"Numbered Links" All FormSpy (aka FireSpy) malware identifies itself as "Numbered Links". The real Numbered Links extension is harmless. See this forum topic for more information. Uninstall the extension. Scan your system for viruses, particularly "FormSpy" and "Downloader-AXM". [146][147]

onFocusReload ? "Alert! Object Event" message. Uninstall onFocusReload. [149]

ProCon Prior to 1.5.2 Replaces all words on webpages with asterisks (******) if set to "censure" words. Fixed in version 1.5.2. Uninstall ProCon, restart Firefox, reset ProCon preferences in about:config, restart Firefox, reinstall. [150]

? May cause the Firefox 3 "Bookmark this Page" dialog to appear when clicking the Bookmarks menu item. Updating to Firefox 3.0.11 or above should resolve the issue. If the problem persists, disable the extension or remove it in RealPlayer preferences (see above) [159] [160]

SwitchProxy Tool All Causes new Firefox windows to freeze for a few seconds Disable SwitchProxy's auto-update feature [174]

1.2.8.4 Bar at the bottom of the screen which reads: %tabprefsDTD; Uninstall TBP and install it directly from the author's website [177] [178]

ThinkVantage Password Manager Extension 2.0 May cause Firefox to freeze for up to a few seconds when a new window is opened. Disable or uninstall the ThinkVantage Password Manager extension in Firefox via Tools -> Add-ons -> Extensions. (Note: The Uninstall option may be greyed out, if the extension was installed via a Windows Registry entry).

2.0 May cause a "Failure in chrome registration" error when starting Firefox.

Note: In Windows Vista, exiting Firefox, right clicking the Firefox icon and selecting "Run as administrator" may resolve the issue; if not, use the workaround. Disable or uninstall the extension (from Firefox Safe Mode if necessary) if you don't need it. Alternately, find the file tvtpwm_moz_xpi.xpi (usually in "C:\Program Files\Lenovo\Client Security Solution") and open it in Firefox to reinstall the extension. [179][180] [181][182]

2.0 Firefox crashes when opening a pop-up window. Caused by the latest Lenovo Client Security update. Disable the extension or reinstall it by opening the file tvtpwm_moz_xpi.xpi in Firefox (see above) [183] [184][185] [186]

Torbutton Prior to 1.2.5 New windows opened from links (e.g. popups) are blank, possibly due to a conflict with the Google Toolbar. Update to the latest version of Torbutton [187] [188]

Prior to 1.2.4 All bookmarks are missing after upgrading to Firefox 3.6 Update to the latest version of Torbutton [189] [190]

Prior to 1.2.1 Interferes with cookie deletion. May also change Firefox privacy and security settings or cause performance issues. Check Torbutton options or update Torbutton to the latest version (or uninstall Torbutton) then recheck Firefox settings. You may need to delete the file "cookies-nontor.xml" to resolve the cookies issue. For other issues, repair or replace the Firefox profile, if necessary. [191] [192] [193][194]

Update Notifier ? A prompt for a username and password from http://mozdev.elliptic.fr/ asking "Oui?" Uninstall Update Notifier [195][196]

VeryDelicious All Software update screen on opening windows and downloading files. Uninstall VeryDelicious [199]

Web Analytics Solution Profiler/Debugger (WASP) Prior to 1.0.9 On Mac OS, installing this extension sets the ~/Library/Caches/TemporaryItems folder to non-writable, causing Download Error -228 and inability to install add-ons. Open the /Library/Caches/ folder for your Mac user account, context click (right-click) on the "TemporaryItems" folder, choose "Get Info" and, under "Sharing and Permissions", change permissions to "Read & Write". [200] [201]

Web Developer 1.1.8 excessive CPU usage proportional to how many tabs are active; with 50 tabs and no activity, 58% cpu usage when enabled, 8% when extension disabled. Disable this extension, and only enable when you need it

Woot Watcher 1.0.1 (all?) Periodic Firefox hangs, slowdowns, or excessive CPU usage, possibly related to Woot Off events. Disable or uninstall the Woot Watcher extension [203]

XPL LinkScanner 2.6 Causes Firefox to crash when using Yahoo, Google, or MSN Search. This extension may be installed in Firefox as part of "System Suite 8" by AvanQuest. Disable or uninstall "XPL LinkScanner Firefox 2.6" via Tools -> Add-ons -> Extensions. [204][205] [206]

Prior to 1.6.6 Right-click disabled in Firefox 3.5 Update to version 1.6.6.20090220 [208]