Folders you find at once.
Clear symbols, quiet counters and a selection that feels like the Finder.
For Thunderbird. Free.
Thunderbird with the look of macOS.
Glassbird gives Thunderbird the glass surfaces, the controls and the order of the Mac. Your mail, accounts and settings stay just as they are.
For Thunderbird 153 to 161. No account, no tracking.
- Free and open sourceMIT licensed, the code is out in the open.
- No account, no trackingNo usage data, no ads.
- Light, dark, your colourFollows your system's appearance and accent colour.
- Leaves no traceIt only changes the look. Without Glassbird, Thunderbird is as it was.
Design
At home down to the last detail.
Sidebar, message list, reading pane and toolbar follow the design of macOS. Light and dark, in your accent colour.
Messages as cards.
Sender, subject and time at a glance, set in type that leaves room to breathe.
Tools in capsules.
The buttons float in glass above the content and group what belongs together.
Your day in view.
The agenda shows what is coming up next, laid out like the calendar on the Mac.
Reading without distraction.
Header, actions and text in a clear order. Quotes with coloured lines instead of brackets.
Light and dark.
Glassbird follows your system's appearance, with its own shades for both.
Glass
A selection that flies along.
When you switch spaces, the selection glides as a glass capsule to the next symbol and magnifies what it passes over. If you like it calmer, choose frosted glass.
Setup
Set up in two minutes.
Install
Glassbird comes into Thunderbird as an add-on, with no terminal and no restart.
Set it up
An assistant asks about symbols, accent colour, glass and reading view. Skip what you don't want.
Carry on
When an update brings something new, the assistant shows only that and ticks off what you have done.
Glassbird Pro
Turn mail into work that moves forward.
Board, search, notes, reminders and writing with AI: Glassbird Pro is an add-on of its own for Thunderbird on Windows, Linux and Mac. It matches the look and runs without it too.
Pricing
Pay once. Keep it.
Glassbird itself is free. You pay for Glassbird Pro once, with twelve months of updates included. After that, your version keeps working with the Thunderbird versions it supports; renewing for another twelve months costs €15, no subscription. A renewal unlocks new features in versions released after that.
Free
€0
The Glassbird look and the basics of Pro.
Get it or download it right herePro Beta
€29.99
Once, with twelve months of updates. After that, twelve more months for €15 at a time, if you like.
Try for 30 daysBusiness Beta, in progress
€49
Per seat, once, with twelve months of updates.
All prices are final prices in euros. As a small business under § 19 of the German VAT Act (UStG), we charge no VAT. You pay through Stripe by credit or debit card, PayPal or SEPA Direct Debit. A renewal is paid once too and never renews by itself. We sell to buyers with a billing address in the European Economic Area, that is the EU, Iceland, Liechtenstein and Norway.
System requirements: Thunderbird for desktop computers from version 153 and an internet connection to activate the licence key and have it checked at least every 90 days. Some features need the free companion add-on Glassbird Pro Experiments, currently for Thunderbird 153 to 161. Mozilla plans to restrict such interfaces in the regularly updated Thunderbird release, currently not before summer 2027. Thunderbird ESR and Betterbird are not affected as things stand. In the view of the add-on Conversations, Translate, Notes and Unsubscribe appear only with the companion add-on. Thunderbird for smartphones and tablets is not supported.
What each plan includes
| Feature | Free | Pro | Business |
|---|---|---|---|
| Glassbird look (separate, free add-on) | |||
| Board with mail cards | |||
| Search with quick actions | |||
| Notes in Thunderbird | |||
| “Aa” format bar while composing | |||
| Tasks with Nextcloud or Thunderbird | |||
| Writing with AI, with your model | |||
| My style and writing skills | |||
| Assistant and follow-ups | |||
| Note sync with Nextcloud, Obsidian, Joplin | |||
| Send later | |||
| Unsubscribe in one click | |||
| Dashboard, news and read later | |||
| Paperless and Nextcloud files | |||
| Snippets and command palette | |||
| Automations through MCP | |||
| DKIM check in the mail header | |||
| Browser extension | |||
| Account colours and online meetings | |||
| Phone in Thunderbird | |||
| CRM with deals and reports |
Privacy
Honest about what's inside.
No tracking.
Neither Glassbird nor Glassbird Pro sends usage data. No analytics, no ads, no account. Your mail, notes and boards stay on your computer.
Your AI, your choice.
The AI features are off until you set them up. A local model is recommended; then nothing leaves your computer. Glassbird Pro always shows where a text is going and asks first before documents or your style profile go to a cloud provider.
Full access, said openly.
Some things Thunderbird allows extensions only through so-called experiments: the look of the interface in Glassbird, the format bar, calendar data or the phone in Glassbird Pro. That is why Thunderbird mentions full access when you install. Glassbird Pro puts these parts into a separate, optional companion add-on, Glassbird Pro Experiments. Without it, Pro runs with a little less.
Frequently asked questions
Does Glassbird change my mail or accounts?
No. Glassbird only changes the look. Where you have not chosen anything yourself, it sets up to four values (two lines per card, tintable symbols and, on the Mac, the system font and scroll bars that fade out) and reverts them when you remove it.
Which version of Thunderbird do I need?
Thunderbird 153 to 161, that is the current ESR and the release versions. When a newer Thunderbird comes out, Glassbird follows with an update. Betterbird works too. Glassbird uses interfaces that Mozilla plans to restrict in the regularly updated release, currently not before summer 2027. Thunderbird ESR and Betterbird are not affected as things stand.
Does Glassbird run on Windows and Linux?
Glassbird is designed for the Mac and tested there. It runs on Windows and Linux, with symbols from free icon sets; it has not been tested thoroughly there yet.
Do I need Glassbird Pro?
No. Glassbird is a complete, free add-on. Pro is a separate add-on for everyone who wants to organise more with Thunderbird, and it comes with free basics: board, search and notes.
What happens after the twelve months?
Your version keeps working with the Thunderbird versions it supports. We then owe you no more updates, not even security or bug fixes or adjustments to new Thunderbird versions; newer versions that Thunderbird installs anyway come without any entitlement to them. A renewal unlocks new features in versions released after that. If you want an entitlement to all updates again, you renew for twelve months for €15: paid once, no subscription. Before the end, the renewal follows on seamlessly; after it, the twelve months count from the renewal. The settings show until when your updates are included. Defects that were there when you bought it, or in an update from those twelve months, we still fix as the law requires, afterwards too.
How do I remove Glassbird?
Like any extension, under Add-ons and Themes. Thunderbird then looks the way it did before.
Glassbird is free. And it stays that way.
If you like it, support its development. A donation unlocks nothing; it keeps the work going.
Support GlassbirdThrough GitHub Sponsors, once or monthly.
Everything to read up on.
Installation, first steps, every setting and what to do when something goes wrong.
To the documentation