Firefox Quantum has been released a few days ago. The new update from Mozilla is one met with excitement from many users, for good reason. Firefox Quantum is extremely fast, gives you a smooth browsing experience, comes with a polished interface, and finally drops https://alternativeto.net/software/yahoo-search/ as the default search engine (Sorry Yahoo, it was time for you to go). There were, however, many users who were frustrated with the new update, as many of the add-ons that made Firefox so useful are no longer supported in the Quantum update.
Firefox Quantum uses the new WebExtensions API, while many add-ons use the older API that is no longer supported in the updated version. This comes as a disappointment, especially for power-users who enjoyed Firefox for the powerful add-ons that were created for it, such as https://alternativeto.net/software/firebug/ or https://alternativeto.net/software/flashgot/ . So if you're one of the users that is unhappy about the lack of backwards compatibility, what can you do?
First, you can search for an alternative extension. Luckily, Firefox makes this pretty easy. If you go into "Add-Ons" from the Firefox menu, you'll see your current add-ons. If you aren't seeing add-ons that you previously had installed, before the update, then it is likely they aren't supported in the new version. If this is the case, you can find them by clicking "Legacy Extensions" on the left-hand side of the page. You should see something similar to the screenshot below (depending on the add-ons installed, of course):
As you can see, if you have an unsupported legacy add-on installed, Firefox now gives you the ability to "Find a Replacement." Which you can do by clicking the respective button, on the right-hand side of the add-on. From there, you'll be taken to a page where you can browse alternative add-ons for the unsupported legacy add-on. In most cases, for most add-ons, this works well and you are likely to be able to find a suitable replacement for the add-on you were attached to.
Second option, you can wait and hope that the developers port the legacy add-on to the new WebExtensions API. Unfortunately, some add-on developers have already announced that they won't be porting to support WebExtensions API, such as https://alternativeto.net/software/firebug/ and https://alternativeto.net/software/selenium-ide/ . Others have announced that updates are in the works, such as https://alternativeto.net/software/lastpass/ and https://alternativeto.net/software/greasemonkey/ , so be sure to check out the website for your favorite add-on to see what the status on an update is.
Finally, if the above two options don't work for you, you can always find and switch to an alternative web browser. You can check out the possible alternatives to https://alternativeto.net/software/firefox/ . But before you think about making the switch to another browser, you should know that Firefox Quantum is an incredible leap forward for Firefox. The improvements are tremendous, and Mozilla's commitment to ensuring future stability with the browser is clear - you may want to stick around with Firefox.
Here is a list of some of the top add-ons that will not be updated and therefore will not work in Firefox Quantum:
Download Status Bar manages every aspect of your downloads (Launch, Show, Scan, Send To, Rename, Checksum, Pause, Resume, Cancel, Clean, Delete), generates Statistics from your Download actions, keeps the History of your previous session downloads and much more.
"Clean Uninstall" cleans fingerprints (such as preferences) left by an add-on from your Firefox profile upon its removal. Usually add-on developers do not clear preferences created by their extension just before extension gets uninstalled.
Firebug integrates with Firefox to put a wealth of web development tools at your fingertips while you browse. You can edit, debug, and monitor CSS, HTML, and JavaScript live in any web page.
FireFTP is a free, secure, cross-platform FTP client for Mozilla Firefox which provides easy and intuitive access to FTP servers.
FlashGot is the free add-on for Firefox and Thunderbird to capture and download embedded links for all types of files (not just flash movies).
Fix the web. Gets rid of a site's cookies and LocalStorage as soon as you close its tabs. Protects against trackers and zombie-cookies. Trustworthy services can be whitelisted.
Session Manager saves and restores the state of all windows - either when you want it or automatically at startup and after crashes. It can also automatically save the state of open windows individually.
Protects against persistent Flash-based tracking by removing Local Shared Objects, manages browser super-cookies, and handles hard-to-delete storage items for secure browsing.
The ultimate web-form recovery solution. Lazarus automagically encrypts and saves web-form data as you type, so that when a form submission fails, your browser crashes, or something else goes horribly wrong, you can skip the hair pulling, return to the page you were on, click...
Random Agent Spoofer is a privacy enhancing Firefox addon which aims to hinder browser fingerprinting. It does this by changing the browser/device profile on a timer. Each browser profile has been tailored to match the actual values used by the target browser as much as...
FireSSH is a free, cross-platform SSH terminal client for Mozilla Firefox. Written entirely in Javascript!
All-in-One Sidebar (AiOS) is a sidebar control, inspired by 
Opera . Click on the left edge of your browser window to open the sidebar and get easy access to all your panels.
FireTray is system tray extension for Linux and Windows that targets 
Mozilla Firefox, 
Thunderbird and 
SeaMonkey.
Customize menus : Helps removing, moving and renaming menus and menu items New feature: Now you can change or disable any of used keyboard shortcuts Support: Firefox, Thunderbird and SeaMonkey.
Shows a popup on tabs and enables you to preview and navigate tab contents through popup. Major features are:
Tweak your FindBar the way you like it!
Main features:
Torrent Tornado is a BitTorrent client for Firefox and SeaMonkey that allows users to download Torrents directly from their browser without any additional software.
ReminderFox displays and manages lists of reminders and ToDo's. ReminderFox makes sure you remember all of your important dates via easy-to-use lists, alerts, and alarms, right in your browser without the need for a separate calendar program.
The ReloadEvery extension adds the funcionality to reload the web page you are viewing every so many seconds or minutes. The function is accessible via the context menu (menu you get when you right click on a web page) or via tab context menu (in Firefox 4.0)
Integrates location bar and search bar into one. Shows search and url suggestions. Quickly switch search engine using search keywords. Provides different auto-complete popup styles for compact displays.
Classic Theme Restorer is a Mozilla Firefox extension that was created in response to the negative feedback against the introduction of the Australis theme in Firefox 29: since then, the main purpose of Classic Theme Restorer is to restore old user...
View and manage downloads from a tidy statusbar.
This was a remake for old well-known addon 
Download Statusbar .
View and manage downloads from a tidy statusbar. Despite its compact size, Download Manager (S3) packs in more useful features th.
Firefox add-on that lets you change headers and request parameters before they're sent to the server. Unlike proxy request modifiers, it's integrated into the browser, so it has no problem with HTTPS connections, client authentication certificates, or other features that...
Does everything for HTML tables: Copy (table/row/column/cell), Sort (multi-column), Search (regex, range operations ...), Filter, Chart (bubble, line, pie, histogram ...), Statistics, Rearrange (column/row), Combine & Compare. Replaces TableTools.
That status bar was removed in Firefox 4.0. While some of the status bar items did find new homes, some did not, and you might not like where they ended up. There were also some nice innovations during the development of Firefox 4.
Multi Links Plus lets you open, copy or bookmark multiple links at the same time rather than having to do them all individually.
Selenium IDE is a browser add-on that records clicks, typing, and other actions to make a test, which you can play back in the browser.
Tab Groups are an easy way to organize a lot of tabs. You can visually group related tabs, switch between groups, and quickly search through all of your tabs to switch to a specific one.
Very simple add-on that closes the current tab and make Firefox forget about the visit: suppressing cookies related to the current page, cleaning (beware : may be partial) the browser history and so on.
Messenger & Notifier for Facebook is an easy way to check 
Messenger from your desktop machine. Clicking on the toolbar icon, renders messenger.com in a small UI attached to the toolbar popup.
QuickMark provides a lightning-fast way for creating bookmarks and keeping them organized. Create and place them in a folder in one mouse sweep or use the shortcuts so your hands don't need to leave the keyboard.
Clear Console addon provides options to clear your cookies, cache, history, html5/local storage, http logins, all of them or restart your browser in a single click.
Buttons for managing site cookie permissions, switching global cookie permissions on and off, browsing cookies, and removing cookies. The same functions are included for local and session storage.
Australis was the code name of the current Firefox theme, which first appeared in Firefox 29. It was an almost complete overhaul not only of the general look of the main browser window, but also of the underlying customization system.
This add-on provides a series of customizable toolbars for your browser, so that you can organize all of your buttons, icons and extras around your window just the way you want them. Every toolbar can be enabled or disabled in the add-on's options immediately.
We will be sure to update the list above if other popular add-ons announce they will not be releasing an update for compatibility with Firefox Quantum.
