What is Firefox?
Firefox is Mozilla's web browser and the only mainstream one that does not use Chromium: it runs on Gecko, Mozilla's own engine, which is why it is the alternative when a site or a standard behaves badly in Chromium browsers. It is free and open source under the Mozilla Public License. On macOS, Mozilla no longer supports version 10.14 or below and directs those users to Firefox ESR, the extended-support release that keeps receiving security fixes. It suits anyone who wants browser diversity rather than a second Chromium.
Verified product facts
- Type
- web browserEditorially reviewed
- Platform
- macOS
- Pricing
- Open sourceDeveloper-stated
- Open source
- Yes
- Developer
- MozillaDeveloper-stated
- Relationship to Nuanyue
- Third-party product — not published by NuanyueEditorially reviewed
- Licence
- MPL-2.0
- Current version
- 157.0Developer-stated
- Official website
- www.firefox.com/
Last updated . Facts marked developer-stated come from the developer and are not independently confirmed; editorially reviewed marks a Nuanyue judgement.
Key features
What Firefox does at a glance.
Gecko rendering engine, independent of Chromium
Extension ecosystem
Private browsing mode
Cross-device sync of bookmarks, history and tabs
Built-in PDF viewer
Tracking protection
What you can use Firefox for
- Browsing the web in a browser that does not use Chromium
- Testing a site against a non-Chromium engine
- Browsing privately with private browsing and tracking protection
- Syncing bookmarks, history and tabs across devices
- Reading PDFs in the browser's built-in viewer
Who is Firefox for?
- Anyone who wants browser diversity rather than a second Chromium
- Web developers who need to test against a non-Chromium engine
- Users on macOS 10.14 or below — Mozilla maintains Firefox ESR for them
Who is Firefox not for?
- Anyone who needs a Chromium-only extension — a small number of extensions exist only for Chromium
- Users who need a browser that renders identically to Chrome — sites tested only against Chrome occasionally behave differently
Limitations
- The current release requires macOS 10.15; macOS 10.14 and below must use Firefox ESR
- A small number of extensions are Chromium-only, and sites tested exclusively against Chrome occasionally render differently
- Apple Silicon support is not stated in the sources Nuanyue tracks
Strengths and trade-offs
What Firefox does well, and what to weigh before choosing it. Points marked developer-stated come from the developer’s own material and have not been independently confirmed.
Strengths
- Runs on Gecko rather than Chromium, so it is the mainstream browser that does not share Chrome's rendering engine.
- Free and open source under the Mozilla Public License 2.0.
- Mozilla maintains an Extended Support Release for users on older macOS versions that no longer receive the current build.Developer-stated
Trade-offs
- Mozilla no longer supports the current release on macOS 10.14 and below, so those users must switch to Firefox ESR.
- Because it is not Chromium-based, sites tested only against Chrome occasionally behave differently, and a small number of extensions exist only for Chromium.Editorially reviewed
First-use experience
What the app asks of you when you set it up. Only established facts appear here; anything we could not confirm is left out rather than guessed at.
- Installation
- Download a .dmg from firefox.com and drag the app to Applications; on macOS 10.14 or below, Mozilla directs users to Firefox ESR instead.
- First launch Developer-stated
- Offers to import bookmarks and history from another browser and to set Firefox as the default.
- System integration Developer-stated
- Can be set as the default browser and optionally prompts to become the default when it is not.
What it does
Firefox is a web browser that does not use Chromium. It runs on Gecko, Mozilla’s own rendering engine, which makes it the mainstream alternative when a site behaves differently in Chromium browsers or when browser-engine diversity matters. It is free and open source under the Mozilla Public License 2.0.
Older macOS versions
Mozilla’s own wording is direct: “Firefox is no longer supported on macOS 10.14 and below.” Those users are directed to Firefox ESR — the Extended Support Release — instead of the current build.
ESR is not a different product so much as a different schedule. It stays on an older codebase and receives security fixes rather than new features, which is what makes it usable both on older operating systems and in managed deployments where rapid change is unwelcome.
Current versions
| Channel | Version |
|---|---|
| Stable | 157.0 (29 September 2026) |
| ESR (current) | 140.17.0esr |
| ESR (legacy) | 115.42.0esr |
Why the engine matters
Every other mainstream browser on macOS is a Chromium build. Firefox being Gecko-based is not a footnote — it is the reason the project exists as a distinct choice. The trade-off is symmetrical: a small number of extensions are Chromium-only, and sites tested exclusively against Chrome occasionally render differently.
Apple Silicon
Recorded as unknown. Neither Mozilla’s download page nor its release notes state the build’s architecture, and Nuanyue leaves that field unestablished rather than inferring it.
Release history
Dated releases recorded for Firefox, newest first, each with the source it was read from.
157.0
Current stable release for macOS.
Source: Official website
Questions about Firefox
Is Firefox free?
Yes. Firefox is free and open source under the Mozilla Public License 2.0, with no paid tier.
Does Firefox still work on older macOS versions?
Mozilla states Firefox is no longer supported on macOS 10.14 and below and directs those users to Firefox ESR, the Extended Support Release, which continues to receive security updates.
What is the difference between Firefox and Firefox ESR?
The regular release ships new features on a rapid schedule. Firefox ESR is held on an older codebase and receives security fixes rather than new features, which is what makes it usable on older operating systems and in managed deployments.Developer-stated
What is the latest Firefox version?
157.0, released on 29 September 2026. The current ESR line is 140.17.0esr, with 115.42.0esr still published for older systems.
Is Firefox based on Chrome?
No. Firefox uses Gecko, Mozilla's own rendering engine. That is the main reason to choose it — it keeps a second engine in the web ecosystem rather than adding another Chromium build.
Alternatives to Firefox
Apps that could replace this one — the same job, a different trade-off.
Brave
Privacy-first Chromium browser with ad and tracker blocking built in.
Both position themselves against Chrome on privacy, but Brave is Chromium-based while Firefox uses Gecko.
Safari
Apple's WebKit-based browser, included with macOS.
Both are non-Chromium browsers on macOS, but Safari uses WebKit and is bundled with the operating system.
Competitors
Direct competitors: overlapping features aimed at the same users.
Chrome
Google's proprietary Chromium-based browser.
The two are direct competitors with different engines; Chrome is Chromium-based and developed by Google.
Compared with
Head-to-head comparisons Nuanyue has published.
Arc
Workspace-style browser, now in maintenance mode.
Both are alternative browsers, but Firefox is actively developed on its own engine while Arc is Chromium-based and in maintenance mode.
Links
Sources
Facts on this page are checked against the sources below. Last updated .
- Firefox — official websiteGrade B
- Mozilla — developer websiteGrade B
- Firefox — documentationGrade C
