A teenage developer's Firefox fork with the browser's best custom UI. It is one of the most popular Firefox derivatives on GitHub, and its creator nearly killed it in 2024 when he briefly took it closed-source out of frustration that companies were forking his fork.
A Firefox fork with a custom CSS-based UI layer, vertical tabs, workspaces, and sidebar extensions, built on the Firefox rapid-release codebase. License is MPL 2.0. The closed-source episode involved a proprietary source-available license that was legally incompatible with the MPL code it had to build on, which is one reason the reversal was practically forced.
Floorp began in 2021 as the project of Ryosuke Asano, then a Japanese high school student, who wanted a Firefox with a serious custom UI. The first public build was Chromium-based (a teenage misstep in its own right), but from version 7.0.0, released in September 2021, Floorp was a real Firefox fork: vertical tabs, workspaces, sidebar extensions, and extensive theming - features Mozilla was years away from shipping natively. It grew into one of the most visible Firefox derivatives, with a passionate community and a dedicated company (Ablaze) behind it.
The drama arrived in March 2024. Asano announced that Floorp would become closed-source because 'companies and organizations would fork a fork that I had created when I was still a teenager' and take the work without contributing back, while he earned nothing for it. The announcement triggered a community crisis, coverage by OSNews, and complaints from contributors who objected to a non-commercial source-available license for a Firefox derivative. Two weeks later the project reversed course, citing community pressure, and re-opened the code. In June 2024 Floorp adopted the Mozilla Public License 2.0 to lock in the open-source status permanently. Asano left Ablaze in May 2025 and continues to maintain Floorp, which in 2026 is on version 12.10.x, built on Firefox's rapid-release base.
First public build, still Chromium-based, is released.
Floorp 7.0.0, the first Firefox-based release, ships.
Asano announces Floorp will go closed-source, citing companies forking his fork.
The project reverses course and re-opens its code.
Floorp adopts the Mozilla Public License 2.0.
Floorp 12.10.x is released; Floorp 13 is in active development.
“There are only a handful of people in the world who know anything about Firefox... my own salary is, of course, zero. It's just not going to last.”
“We have decided to keep Floorp open source.”
Floorp is a standing argument that Firefox's engine is fine and its UX is the problem: a teenager with no resources shipped the browser UI Mozilla kept promising. The 2024 closed-source episode also made Floorp the cautionary tale about the fragility of one-person open-source projects and the perverse incentives of getting forked.