Premium
Download Firefox Nightly for Developers 4.0.0 APK
Version: 4.0.0 (20691755)
Languages: 92
Package: org.mozilla.fenix
Downloads: 383
Target: Android 9.0 (Pie, API 28)
nodpi
Firefox Nightly for Developers notes
Firefox Preview v4.0.0
Login management #1284
In-App Language Chooser #220
Top Sites #6190
Bypassing Certificate errors #6380
Fix persistent undo notification #8472
Initial extension support featuring uBlock Origin #5630
And other bugfixes and improvements.
What's new in Firefox Nightly for Developers 4.0.0
Thank you for testing Firefox Preview! This release includes improvements to search and download, as well as stability and performance bug fixes.
About Firefox Nightly for Developers 4.0.0
Firefox Preview marks a release of the early version for an experimental Firefox browser for Android. Built on GeckoView, Firefox Preview is a pilot for early adopters, developers, and anyone who wants to help make a better, more private Firefox for Android.
Premium
Firefox Preview is the first step in building a better mobile browser: one that’s faster, more secure and more independent than any mobile Firefox browser before it. It will combine the speed, privacy, control, and easy-to-use features you have come to expect from Firefox. Like all Firefox products, it will never sell your data for profit.
If you’re curious about new features and like to tinker with technology, your feedback will be invaluable. All you have to do is install the Firefox Preview mobile app and start using it.
Fly faster with GeckoView
The new Firefox Preview is up to 2x faster than previous versions of Firefox for Android. It’s powered by GeckoView, which gives us the freedom to build a browser that’s faster-than-ever, with the ultimate privacy of Firefox.
And, because GeckoView allows us to make quick updates, you get cool new features even sooner. Firefox Preview is fast by design, featuring a minimalist start screen, and bottom URL bar to take away any distractions that can slow you down.
The GeckoView browser engine uses the same technology that powers the ultra-private Firefox desktop browser. That means Preview is built in-house, so your data is never sold for profit on your mobile phone.
Protect your privacy
At Firefox, privacy and user control are our top priority. Online privacy isn’t just a policy: it’s a right. Firefox Preview lets you explore the latest privacy features for mobile. One of these is Tracking Protection, which is on by default and totally customizable in Firefox Preview.
Get more done
Stay organized with Collections, a new Firefox feature that helps you return to everyday tasks, share tasks across devices, and knock out your to-do list. And, when you join Firefox, you can sync your bookmarks, saved logins, browsing history, and more across all your devices.
Help build a better Firefox
Once you’re up and running, take the app for a test drive. Tell us about your mobile experience–what worked and what didn’t. We’re looking forward to gathering your feedback and learning from it. Please email firefox-preview-feedback@mozilla.com with your comments, or file a bug on Github.
Install Firefox Preview and make an impact on your mobile experience and the future of mobile browsing.
Firefox Nightly for Developers 4.0.0 variants
This release comes in several variants (we currently have 8). Consult our handy FAQ to see which download is right for you.
Version:121.0a1(2015982688) for Android 5.0+ (Lollipop, API 21)
Uploaded:October 29, 2023 at 6:44AM UTC
File size:89.26 MB
Downloads:1,299
Version:121.0a1(2015982592) for Android 5.0+ (Lollipop, API 21)
Uploaded:October 28, 2023 at 6:22PM UTC
File size:89.25 MB
Downloads:35
Version:121.0a1(2015982400) for Android 5.0+ (Lollipop, API 21)
Uploaded:October 27, 2023 at 11:53PM UTC
File size:89.10 MB
Downloads:18
Version:121.0a1(2015982304) for Android 5.0+ (Lollipop, API 21)
Uploaded:October 27, 2023 at 6:33AM UTC
File size:89.13 MB
Downloads:18
Version:121.0a1(2015982208) for Android 5.0+ (Lollipop, API 21)
Uploaded:October 27, 2023 at 2:24AM UTC
File size:89.08 MB
Downloads:15
Version:121.0a1(2015981920) for Android 5.0+ (Lollipop, API 21)
Uploaded:October 25, 2023 at 7:07AM UTC
File size:89.15 MB
Downloads:23
Version:121.0a1(2015981824) for Android 5.0+ (Lollipop, API 21)
Uploaded:October 24, 2023 at 7:50PM UTC
File size:89.24 MB
Downloads:21
Version:121.0a1(2015981728) for Android 5.0+ (Lollipop, API 21)
Uploaded:October 24, 2023 at 6:22AM UTC
File size:89.12 MB
Downloads:20
Version:121.0a1(2015981680) for Android 5.0+ (Lollipop, API 21)
Uploaded:October 24, 2023 at 12:07AM UTC
File size:89.22 MB
Downloads:722
Version:120.0a1(2015981536) for Android 5.0+ (Lollipop, API 21)
Uploaded:October 23, 2023 at 5:37AM UTC
File size:89.37 MB
Downloads:32
Version:158.0a1
Uploaded:September 24, 2026 at 1:57AM UTC
File size:67.07 MB
Downloads:451
Version:157.0a1
Uploaded:September 10, 2026 at 4:40AM UTC
File size:48.14 MB
Downloads:450
Version:156.0a1
Uploaded:August 28, 2026 at 7:42PM UTC
File size:47.84 MB
Downloads:392
Version:155.0a1
Uploaded:August 13, 2026 at 1:25PM UTC
File size:48.15 MB
Downloads:886
Version:154.0a1
Uploaded:July 20, 2026 at 5:02PM UTC
File size:66.41 MB
Downloads:1,552
Version:153.0a1
Uploaded:June 15, 2026 at 2:12PM UTC
File size:65.26 MB
Downloads:1,478
Version:152.0a1
Uploaded:May 18, 2026 at 2:18PM UTC
File size:62.75 MB
Downloads:1,372
Version:151.0a1
Uploaded:April 20, 2026 at 1:22PM UTC
File size:59.06 MB
Downloads:1,602
Version:150.0a1
Uploaded:March 23, 2026 at 11:36AM UTC
File size:58.14 MB
Downloads:1,415
Version:149.0a1
Uploaded:February 23, 2026 at 1:04PM UTC
File size:57.05 MB
Downloads:2,564
