When comparing Opera GX vs Mozilla Firefox, the Slant community recommends Mozilla Firefox for most people. In the question“What are the best desktop web browsers?” Mozilla Firefox is ranked 3rd while Opera GX is ranked 35th. The most important reason people chose Mozilla Firefox is:
Firefox [scores strongly on HTML5 feature support](http://html5test.com/results/desktop.html). Though not as strongly as Chromium/Chrome browsers do.
Specs
Ranked in these QuestionsQuestion Ranking
Pros
Pro Customizable
Browser is highly customizable, with dual colors, sounds, effects, bookmarks and tabs and much more.
Pro Built-in adblocker
Pro Built-in tracker blocker
Pro GX Control
Lets you limit the network traffic, RAM and CPU usage of the browser.
Pro Built-in messenger services
It has built-in Whatsapp, Telegram, Twitter, Instagram, Facebook Messenger and much more and this feature itself is better than most of the browsers out there.
Pro Built in music player
It has a built in music player which you can listen to Spotify, Youtube Music and Apple Music in the background.
Pro Very fast
Using the chromium engine, this browser is as fast as Chrome and Edge.
Pro Lots of Add-Ons
Opera Store and Chrome Store is available for this browser with millions of add-ons.
Pro It is good for gaming
Pro Opera Sync
You can sync everything via other devices and it is password protected apart from a standart login.
Pro Built-in news reader
Apart from other browsers like Edge which forces you to read only their feed, you can add any feed and news channel, and read them anytime.
Pro GX Cleaner
Lets you clean browser data easiliy.
Pro GX Corner
It's a page designed for game lovers with news, prices, deals and much more about the latest games.
Pro My Flow option
The browser has a built-in software which lets you send everything from files to pictures, and messages to yourselves via "My Flow" to your other devices and phones.
Pro Built in dark mode system
Pro Built-in VPN
It's a free service and unlimited (but it leaks your IP address). Perfect and very easy to use.
Pro Built in Ambient Music player and button sounds
The dynamic background music is an ambient downtempo that will immerse you further in your gaming-themed browser. Actively browsing, clicking and typing intensifies the music, for example, while slowly scrolling and reading will take the music down a notch. This dynamic reaction to your activity blends into the background when you’re in focus-mode, so you often don’t notice it until you miss it.
Also when you type via keyboard , a very nice click sound is there to feel like The Matrix computer engineer.
You can switch these sounds off.
Pro Strong HTML5 feature support
Firefox scores strongly on HTML5 feature support.
Though not as strongly as Chromium/Chrome browsers do.
Pro Syncs between devices
Firefox Sync is an optional feature in Firefox that allows syncing bookmarks, passwords, and add-ons between devices.
Pro Free, open source and community driven
Firefox is available as a free download. All Mozilla software is licensed under the Mozilla Public License. Instructions on how to obtain the source code can be found here.
Pro Respects your privacy
Mozilla is one of the first browsers that advocates privacy. They believe that internet should be in the user's control and not those who run the websites, and so they give tools inside the browser to make the user be more in control.
Pro Strong developer tool
The built-in developer tools have been merged with the popular FireBug extension since FF57.
Pro High performance
The Firefox Quantum update (FF57) greatly increases the render speed and general performance of the browser, by taking better advantage of the user's hardware.
Pro Reader View
Reader View in Firefox allows users to read an article without any distractions by removing ads, unrelated elements and other distractive objects (similar to Microsoft Edge's Reading Mode and Safari's reader mode).
Pro One of the few browsers not using Chrome's Blink engine
Firefox uses its own rendering engine (called Gecko), instead of Google-controlled Blink like the vast majority of other browsers.
Pro Fast
With new integrations focused on security and performance, Firefox is faster and less likely to have problems during use than ever before.
Pro Open Source
Open Source means that you can see the source code. So everybody even if they don't work for Mozilla is able to look what the browser does in the background. So you can be 100% sure that Firefox doesn't have hidden "spy features" unlike Google Chrome.
Pro Good font rasterizing
Font rasterizing on Windows is much better than in competitors. Even smaller text is clear and contrast.
Pro Automatically updated
Firefox is automatically updated on the platforms where it makes sense.
Pro Uses less resources
Firefox 57 (Quantum) and newer uses less resources than ever. It is proven with benchmark done by AppleInsider.
Pro Dark theme
Beyond the toolbar and tabs, it darkens UI elements such as the URL-bar, pop-downs, new-tab page and more.
Pro Awesome customizability
Great library of add-ons.
Pro Tagging bookmarks
Firefox is one of the few browsers that you can tag your bookmarks. You can view a list of tags and can search your bookmarks in the address bar with tags.
Pro Really independent browser
It's not dependent on Google.
Pro Screenshot tool
Powerful screenshot tool built right into the browser.
Pro Ethical and pragmatic company mission
The Mozilla Manifesto outlines the company's mission and principles. Paraphrasing, they want the Internet to be a free and open resource, and to enable individuals to get the best use of that resource. They do this by creating open source software to which anyone may contribute, so long as such contributions fit with their principles (both ethical and technical).
Pro A lot of add-ons
An enormous number of add-ons.
Pro Fast bookmark management
In order to add an open page to the bookmark bar, the tab can be dragged down and is added immediately.
Pro Built-in privacy protection
Blocks tracking cookies, finger print scanners and Cryptominers by default. Can be changed to the user's individual needs.
Pro Lower memory fingerprint than competitors
Firefox used to be a trailer in memory usage, but as of 2017 it's less hungry for memory than competitors like Edge, Chrome, Safari and Opera.
Pro Text-to-speech (with adjustable speed) without add-ons
Firefox Reader Mode includes Narrate, a feature that adds text-to-speech functionality to the browser.
Pro Very secure
Pro Firefox experiments
FF experiments are Mozilla projects available from FF Test Pilot, such as Firefox Colour, witch lets you customise your browser theme to your liking!
Pro Firefox Lockwise password management
Helps store your usernames and passwords. Lockwise also lets you know if any of the sites you have login details for have had their (and potentially your) data leaked!
Pro HTML5 video preload
The only web browser that only preloads entire HTML5 video which is useful for slow internet.
Pro Mobile
Firefox has a solid mobile app.
Pro Integration with Pocket
Firefox comes with built-in Pocket integration that can allow users to quickly save the article for a read it later function to easily find any articles saved in Pocket from various sources and devices.
Pro Installed by default on many Linux distributions
Many Linux distributions come preinstalled with Mozilla Firefox
Pro About:config
Master about:config and uBlock Origin, and all Firefox-based browsers will be yours.
Pro WebRender
The newer versions of it will soon use WebRender to render webpages, which'll make it much more efficient by utilizing GPU to paint webpages.
Pro UI
UI is better than any other chromium-based browser.
Cons
Con Owned by a Chinese consortium
Although it has many privacy and security features, Opera is owned by a Chinese company and everything you do online is spied by China probably.
Con GX Control not so effective
RAM, CPU and Network limiter is not so effective.
Con May not be for everyone
It's a gaming themed browser with dark and colorful interface. May not be everyones taste.
Con Opera GX for Android is bad
Slow.
Con Slow opening time
When compared to Edge, Chrome and Brave, this browser starts up a little later due to many features it has inside.
Con Practically spyware
Owned by a Chinese company.
Con Some built-in advertising
With their new "pocket" feature, they offer advertisements built-in.
Con Cannot directly translate page
Unlike Google Chrome, if you visit a website with a different language, you cannot translate it, which is a bad user experience for some.
Con Lack of keyboard shortcuts customization
Keyboard shortcuts can not be changed in a user-friendly way.
It is also difficult to manipulate addons with hotkeys.
Con When you search in a website (Ctrl + F) there are no marks appearing in the right scrollbar
All Chromium based browsers have this feature.
Con Installs Addons with updates
Mozilla is installing/integrating addons with every update like the Mr. Robot promotion - it also has integrated Pocket that spams you every time you open the browser or a new tab with partners of Pocket.
Con Uses Google as its default search engine
Which is pretty ironic for a browser that's focused on "privacy".
Con Sometimes very buggy and slow
On sites like twitch.tv chat scrolling is still not fixed. Compared to other browsers Firefox is still very slow and feels sluggish.
Con Uses GTK on Linux/BSD
This makes the integration on non-GTK Desktop Environments very hard.
Con Multi Profile is not user friendly
Multi profile requires commandline -no remote to use and open about:profiles to create manually (on Chrome, you can instantly create them on right top user button).
Con Antivirus has False positives
All Downloads in Firefox are scanned for viruses, but there are a lot of false positives.
Con Doesn’t support multiple languages for spell check
If you write in multiple languages, you need to manually switch the spell check language.
Con Terrible user interface
Con Crappy license
Cannot redistribute binary after source code modification.
Con Major updates may break any installed add-ons
Con Now forces install and use of snap
Only on Ubuntu
Con New icon looks ugly
Con GTK Themes styles the HTML forms
If you're in Linux and you use a dark GTK theme that uses white text and come to a webpage that forces black text on html-forms buttons you will get black buttons with unreadable black text.
Con Doesn't care for its original guidelines/goals
Mozilla originally aimed to be the "good guys" with user choice and privacy in mind. Their current leadership cannot be trusted to hold those goals in high regard:
1) Added Pocket - a privacy data sensitive plugin, made it mandatory
2) Tried to sneak in advertisement as "drive-by hack", backpedaled unconvincingly once users complained
3) Tried to randomly inject a small percentage of Firefox downloads in Germany with a data collecting plugin (Cliqz) that tech-savy Germans consider adware (no opt-out question asked).
Con It's a memory hog even though Mozilla claims it is not
Mozilla claims it's using 30% less RAM than Chrome but in real life tests it uses much more.