BirdOne

One-line layout: tabs and unified toolbar share a single row, global search hidden (use CTRL+K).

Tested on Thunderbird 152 (Supernova UI, 115+ required) on Windows.

BirdOne is configurable through CSS variables. See all options → docs/customisation.md

The repository also contains userContent.css for the mail body, compose editor and settings page.

It is work in progress and currently not recommended: it still applies the colour layer that userChrome.css no longer does. BirdOne works without it.

What about Firefox?

You are looking for FoxOne!

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Installation and Customisation | Concept inspired by @NeroWolfe75's one-line experiment from 2023 | License: MIT