When comparing Firefox vs Opera, the Slant community recommends Firefox for most people. In the question“What are the best Android web browsers?” Firefox is ranked 3rd while Opera is ranked 8th. The most important reason people chose Firefox is:
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](https://developer.mozilla.org/en-US/docs/Mozilla/Developer_guide/Source_Code/Downloading_Source_Archives).
Ranked in these QuestionsQuestion Ranking
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 Functionality can be extended with add-ons
By far the best browser if not using an adblocking app like AdAway or Adguard. Adblocking, Privacy, Themes/Stylish, etc. Add-ons make Firefox the best total package mobile browser... You may even forget you're using a mobile 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 Built-in reading mode
Reading mode allows removing everything on a page but the text. It removes ads, styling and anything else that could get in the way of a comfortable reading experience.
Pro HTML5, mobile video support
Firefox for Android supports HTML5, and with support for multiple video formats, you can watch videos right in the browser.
Pro Sync with desktop browser
Keep track of all your bookmarks, passwords, open tabs, and history on the go.
Pro Great efficient and intuitive UI
The scrolling and response is generally faster than Chrome on my Android devices.
Pro Built-in ad blocker
Pro Send to device feature
You can send a tab to your mobile or another device, or vice versa.
Pro AdBlocker onboard
It's possible to add own filter lists. The internal adblocker is faster than any external.
Pro Compatible with Chrome extensions
Since Opera is built on WebKit, the same engine Chrome (among other browsers) is built on, it was possible for Opera developers to allow Chrome extensions to run in their browser.
Pro Video pop-out feature.
You can pop-out any video and it will stay on top while you are surfing on other tabs.
Pro VPN onboard
Free and fast VPN onboard, includes Germany, Canada, USA, Netherlands, Singapore.
Pro Strong HTML5 feature support
Opera scores highly on HTML5 feature support.
Pro Opera turbo
Opera has a functionality called Turbo which increases browsers speed and reduces data consumption considerably by compressing the data that's found in a web page.
Pro Battery saving mode
Opera is full of user controlled settings. Everything can be imported and exported even RSS feeds. It can be skinned in a variety of different themes or it can be extended through the use of a large number of plugins available.
Pro You can install extensions on the sidebar
Unlike other browsers, you can install add-ons such as tabs, bookmarks, history, sessions, notes, and extension manager in the sidebar. So you have the flexibility to use it for your purpose.
Pro Free and open source
Source code available on GitHub.
Pro Opera can have extensions from Opera Addons & Chrome Store websites
Opera supports cross-browser extensions. Opera Addons site keeps quality up compared to Chrome Store. Full of useful extensions, Opera also supports extra APIs like Speed Dial API, Extension Sidebar API and Stash API meaning wider variety of extension possibilities than in Chrome.
Pro Speed Dial
Opera's Speed Dial (new tab page) has the ability to hold as many websites as you want, and you can customize it almost however you want. You can also organize the websites on the Speed Dial into folders.
Pro Opera Sync
Opera Sync allows you to synchronize your bookmarks, passwords, and more from any computer, phone, or tablet.
You can save the Opera's setup files on a USB hard drive and run its portable version anywhere.
Pro For Opera 2017 & 2018 gonna be time of new
Opera got Reborn UI as the first implementation from Opera Neon concept browser. Snap -feature is next. Opera constantly improves it's basic functionality - unlike Chrome.
Pro Fast video loading
Opera loads videos faster, making it useful for slow internet connections.
Con Can't play flash videos
Due to security concerns, Firefox does not include Flash support by default.
Con Reading mode removes some images and videos
Reading mode removes non-textual elements that are not part of the article, but it retains images and videos that are part of the feed node (rss).
Con Original version using Presto engine is dead
Current version is built on WebKit/Blink, which means it shares cons of Chromium: high RAM usage, lack of customizability.
Con Uneditable default search providers
It can not delete or replace already built-in search services such as Yahoo, Google, DuckDuckGo, and Wikipedia.
Con Opera is owned by a Chinese Consortium
Who certainly need to conform with Chinese government requirements to let them infiltrate everything you do online…
While Opera is currently available gratis (without monetary charge), it is currently not libre (meaning that it does not allow users to view the source code used to create, to modify that code, or to redistribute modifications) and is therefor neither free nor open-source software.
Con Extension icons not directly moveable
Con Fewer extensions
Con Cannot select tabs
Unlike in Chrome and Vivaldi, one cannot select multiple tabs to move to another/new window.
Some buggy or confusing behavior with the bookmarks bar and moving tabs.
Also, for me, the entire windows turn black after a while.
Con Basically a Chrome clone
The latest versions of Opera are basically Chrome clones, so they really don't add anything new.