# Thorium: a Chromium fork with restored codecs, JPEG XL and classic Chrome UI

> Thorium is a Linux Chromium fork built with LTO, PGO and SIMD-targeted builds, plus restored FTP, JPEG XL, Widevine and the pre-M124 Chrome interface. Here is what the repository actually documents, and where the trade-offs sit.

**Alex313031/thorium** — Chromium fork named after radioactive element No. 90. Source code and Linux releases. Windows/MacOS/ARM builds served in different repos, links are towards the top of the README.md.

- Repository: https://github.com/Alex313031/thorium
- Website: https://thorium.rocks/
- Stars: 7,528 · Forks: 285
- Language: C++
- License: BSD-3-Clause
- Published: 2026-09-22 · Updated: 2026-09-22 · Language: en
- Canonical page: https://hysenlabs.com/projects/alex313031-thorium

## What Thorium changes compared with stock Chromium

Thorium is a Chromium fork for Linux, named after the radioactive element with atomic number 90. The README states that it is always built against the latest Chromium LTS version, and that the intent is to behave like Google Chrome while adding patches and build settings that upstream does not ship.

The feature list is concrete rather than aspirational. JPEG XL support is restored and enabled by default. FTP URL support is restored and enabled by default. Widevine, all codecs, and proper HEVC/H.265 support are included on Linux and Windows. Experimental MPEG-DASH support is present. The classic Chrome UI from before M124 is restored in place of Chrome Refresh 2023, gated behind the flag chrome://flags/#thorium-2024, and the classic Download Shelf is available behind chrome://flags/#download-shelf.

Privacy defaults are also changed. Do Not Track is enabled by default, Global Privacy Control is added and enabled, FLOC and the Privacy Sandbox are disabled, and prefetch settings are adjusted. DoH patches come from Bromite. Full URLs including trailing slashes are shown in the address bar by default. The Default Browser Infobar and in-product help promos are disabled.

This is a fork for people who want a specific behaviour set, not a general-purpose browser recommendation. If none of those items matter to you, the patch surface is mostly invisible.

## How the build pipeline and SIMD variants work

The performance story rests on compiler configuration rather than runtime tricks. The README describes LTO, CFlag, LDFlag, LLVM Loop and PGO optimizations, and points to docs/PATCHES.md for the full flag list. The repository root carries args.gn and win_args.gn, plus build.sh, autobuild.sh, build_android.sh, build_mac.sh, build_win.sh, setup.sh, get_repo.sh, trunk.sh and tot.sh. A gclient file and a depot_tools directory sit alongside them, which matches the standard Chromium checkout workflow rather than a custom build system.

The interesting part is the per-CPU release matrix. Releases are named for the SIMD instruction set they target: SSE3, SSE4, AVX and AVX2. A reader who downloads the wrong one gets a binary that either refuses to start or runs without the intended vectorization. The README addresses this directly by pointing to docs/ABOUT_RELEASES.md for guidance, and the repository includes check_simd.sh, which is presumably the script that inspects the host CPU. The check_simd.sh file is present in the top-level listing; the README does not describe its output format.

One structural detail worth noting: the repository is not a single source of truth for all platforms. Windows, macOS, Android, Raspberry Pi, 32-bit and legacy Windows builds live in separate repositories, and the README links to them near the top.

## Installing Thorium on Linux and enabling the restored features

The README does not give a step-by-step install procedure in the body text. It states that the Thorium website at https://thorium.rocks/ hosts a deb repository for auto-updating on Linux, and that releases with the SIMD names are published on the GitHub releases page. The README also notes that the Chrome APT sources.list addition is removed during installation, so installing Thorium does not silently add Google's repository.

Because the repository does not document the exact apt commands, the safe path is the website's deb repository instructions rather than a guessed one-liner. What the repository does document is the post-install configuration surface, which is where the fork's value shows up. The two flags below are quoted from the README's feature list.

```bash
# Open these in the address bar after launch
chrome://flags/#thorium-2024
chrome://flags/#download-shelf
```

Enabling thorium-2024 restores the classic Chrome UI from before M124. Enabling download-shelf brings back the classic download shelf. Both are described as flags rather than defaults, which means a fresh install still shows the newer interface until you toggle them.

For anyone building from source rather than installing a release, the repository root contains the expected entry points. These file names are taken from the top-level listing, not from a README walkthrough.

```bash
./setup.sh
./build.sh
```

The README does not document what setup.sh does beyond its name, so a source build should be treated as an expert path requiring a working Chromium toolchain. Release installs avoid that entirely.

## Where Thorium is the wrong tool

The most immediate limitation is platform scope. This repository is the Linux fork. The README directs Windows users to Thorium-Win, macOS users to Thorium-Mac, Android users to Thorium-Android, Raspberry Pi users to Thorium-Raspi, 32-bit and old-CPU users to Thorium-Special, and Windows XP through 8.1 users to thorium-legacy. If you are not on Linux, this repository is not the one you want, even though the homepage is shared.

Release cadence is the second issue. The three most recent releases are tagged M152.0.7977.55, M151.0.7922.72 and M150.0.7871.47, and every one of them carries the label Beta Release in its title. The README claims builds track the latest Chromium LTS, but the published artifacts are labelled beta. Anyone who needs a stable channel with a documented support window should read that labelling literally.

Third, the feature set is a liability in some environments. Restored FTP support and restored JPEG XL are deliberate divergences from upstream Chromium. Organizations that require a browser matching upstream behaviour, or that rely on upstream security response timing, are better served by Chromium itself. The README also documents that Do Not Track and Global Privacy Control are enabled by default, which can change what analytics and consent tooling observes.

Finally, the README makes no claim about enterprise policy support, managed deployment, or an update channel beyond the deb repository. Absence in the README is not proof of absence in the code, but it does mean you cannot plan a managed rollout from the documentation alone.

## Chromium, Ungoogled Chromium and Brave as alternatives

Plain Chromium is the closest alternative and the clearest contrast. It tracks the same upstream code, but it does not ship Widevine or all codecs by default, does not restore JPEG XL or FTP, and does not offer SIMD-targeted builds. If your only requirement is a browser without Google branding, Chromium is the smaller commitment.

Ungoogled Chromium takes the opposite approach to Thorium's privacy patches. The README states that some Thorium flags are added from Ungoogled Chromium, so the two overlap, but Ungoogled Chromium's goal is removing Google integration while Thorium's is behaving like Chrome with a specific patch set. Thorium keeps Widevine and the codec stack, which Ungoogled Chromium does not prioritize. That difference decides the choice for anyone who needs DRM playback.

Brave is a different kind of fork: it is built around its own ad-blocking and rewards stack rather than around restored upstream features and compiler tuning. Thorium's README lists Brave Search as an added search engine, not as a design influence. If you want content blocking out of the box, Brave answers that directly; if you want the pre-M124 Chrome interface and JPEG XL, Thorium is the one that documents them.

The honest summary is that Thorium competes on build tuning and restored features, not on privacy architecture. Its privacy changes are a list of defaults, not a separate threat model.

## Licence, maintenance and upgrade cost

Thorium is licensed under BSD-3-Clause, and the repository carries LICENSE.md at the top level. Chromium itself is distributed under a BSD-style licence, so the fork's licence is consistent with its upstream. Redistribution of built binaries carries the usual obligation to preserve copyright notices; that is a general property of BSD-3-Clause and not legal advice.

The last push to the repository was on 2026-08-23, and the most recent release, M152.0.7977.55, was published the same day. The repository is not archived. That is a recent enough signal that work is ongoing, but the release titles all say Beta Release, so plan upgrades around that label rather than around an LTS promise.

Upgrade cost is dominated by the SIMD matrix. Because releases are published per instruction set, an upgrade is not a single download: you re-select the correct SSE3, SSE4, AVX or AVX2 artifact each time, or rely on the deb repository at thorium.rocks to handle it. Machines that get moved between hosts, or VMs that change CPU feature exposure, are where this bites. If you build from source instead, the cost is a full Chromium checkout and compile, which the presence of depot_tools and gclient in the repository makes explicit.

## Conclusion

Adopt Thorium if you run Linux on a recent x86-64 CPU, want JPEG XL and FTP back, and prefer the pre-M124 Chrome interface over Chrome Refresh 2023. Do not adopt it if you need Windows, macOS, Android or Raspberry Pi builds from this repository, since the README points those to separate repositories, or if you depend on a stable channel rather than the beta-tagged releases. Before installing, check which SIMD level your CPU supports against docs/ABOUT_RELEASES.md, and confirm the deb repository at thorium.rocks matches your distribution.

## FAQ

### How do I install the Thorium browser on Linux?

The README points to https://thorium.rocks/ for a deb repository that supports auto-updating on Linux, and to the GitHub releases page for SIMD-specific artifacts. It does not list the exact apt commands in the README body.

### How do I use Thorium?

Install a release matching your CPU's SIMD support, then launch it like any Chromium-based browser. To get the fork's distinctive interface, enable chrome://flags/#thorium-2024 for the pre-M124 UI and chrome://flags/#download-shelf for the classic download shelf, as the README describes.

### How do I install Thorium?

On Linux, the README directs you to the deb repository at thorium.rocks or to the releases page, where builds are named by SIMD level. Other platforms are served by separate repositories linked near the top of the README.

## Sources

- [Alex313031/thorium on GitHub](https://github.com/Alex313031/thorium)
- [License: BSD-3-Clause](https://github.com/Alex313031/thorium/blob/main/LICENSE)
- [Project website](https://thorium.rocks/)
- [README](https://github.com/Alex313031/thorium/blob/main/README.md)
- [Releases](https://github.com/Alex313031/thorium/releases)

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Hysen Labs editorial analysis, written from the project's own repository and release notes. Cite the canonical page: https://hysenlabs.com/projects/alex313031-thorium