New Alpha Release: Tor Browser 15.0a4

by morgan | October 16, 2025

Tor Browser 15.0a4 is now available from the Tor Browser download page and also from our distribution directory.

This version includes important security updates to Firefox.

Release Candidate

If all goes as planned, this will be our last alpha release in the 15.0 series before it is promoted to stable in the last week of October. Next week we will be focusing primarily on QA and ensuring all the various features and scenarios supported in Tor Browser still work as expected. This QA work will be tracked in the following gitlab issues:

As we reach the home stretch, now would be a great time to download and try out Tor Browser Alpha! We would appreciate it if the community would evaluate and exercise these following changes:

🤖 Removal of Various AI Features

Over the past year Mozilla has been working on integrating various AI features and integrations into Firefox (e.g. the AI chatbot sidebar). Such machine learning systems and platforms are inherently un-auditable from a security and privacy perspective. We also do not want to imply recommendation or promotion of such systems by including them in Tor Browser. Therefore, we have done what we can to remove such features from the browser.

☁️ Rename meek-azure pluggable-transport to just meek

In the past, we have used various cloud platform to host meek pluggable-transport backends including Google, Amazon, and Azure. However, as time passed these backends have moved and migrated and thus the cloud provider-specific name has become an historical artifact. Therefore, we have dropped the Azure part of the name and now just call it meek. Let this be a lesson to you about naming things!

🟪 Improved Dark Theme Support in Browser Chrome

We have improved the styling for our various Tor Browser-specific UI components for dark browser themes. All of our various purple elements should now look like they belong.

🦊 Removal/Replacement of New Firefox/Mozilla-specific Branding and Features

As part of ordinary incremental UI updates over the past year and the implementation of new features, Mozilla has added various new brand assets and service integrations. This includes things like those cute little fox graphics, Firefox Home, and the new History Sidebar. As of this release, there should not be any more Firefox or Mozilla specific branding, features, or service integrations accessible in Tor Browser. The new history sidebar in particular has been replaced with the legacy history panel from previous Tor Browser versions.

🐧 Updated Emoji Font for Linux

We have included the Noto Color Emoji font with our Linux builds. Linux users should now have all the latest and greatest emoji provided by Noto Emoji.

🈴️ Improved CJK Glyph Rendering

At the suggestion of a cypherpunk, we have swapped out the Noto font family for Jigmo. This should allow more Chinese, Japanese, and Korean graphemes to render accurately in web content.

✉️ Letterboxing Styling Improvements

We have tweaked our custom styling of the web-content letterboxing feature to confirm with and adapt to Firefox's own styling changes in Firefox 140. These tweaks should also play nicely with upstream's vertical tabs feature.

🚫 WebAssembly Restrictions Now Managed by NoScript

Historically, we have disabled WebAssembly globally when the browser is in the Safer and Safest security levels. However, with the latest Firefox version this has proven to be too aggressive, as doing so broke functionality in the built-in PDF reader. We therefore now rely on the NoScript extension built into the browser to handle disabling WebAssembly functionality in web content while the browser is in the Safer and Safest security levels, while also allowing WebAssembly to run unhindered in safe+privileged contexts like the PDF reader.

🔍 Stopped Hiding Protocol in URL on Desktop

Mozilla has reversed course on when the protocol portion (e.g. http or https) of the URL in the URL bar is hidden since Firefox 128. We used to have logic in one of our patches around Onion Services (which are always end-to-end encrypted regardless of the application-level protocol used) to follow whatever Firefox does for https. However, with the latest changes in Firefox, this patch became a bit gnarly to apply correctly so we took a step back and thought to ourselves, why are we even conditionally hiding this from the user?

So for now, we have decided not to hide the protocol from the user on Desktop platforms using a supported Firefox pref. We continue to follow upstream and always hide the protocol in the URL bar on Android (where horizontal space is at a premium). Users of Tor Browser Android can simply click the icon in the URL bar to get all the info about a websites HTTPS usage.

Send us your feedback

If you find a bug or have a suggestion for how we could improve this release, please let us know.

⚠️ Reminder: Tor Browser Alpha release channel is for testing only. If you are at risk or need strong anonymity, stick with the stable release channel.

Full changelog

The full changelog since Tor Browser 15.0a3 is:

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