An optimization-first Chromium browser for Windows. Fast, memory-smart, private, and honest.
⚠️ Pre-release. v0.0 (a from-source proving build) is complete; v0.1 — the first downloadable release — is in progress. Watch Releases. Nothing to download yet.
Slipstream Browser is an open-source Chromium fork built on the Thorium optimization patch set (AVX2, ThinLTO, PGO official builds), with additional debloating, privacy hardening, and memory tuning on top — and with the things that make Chromium practical left fully intact, starting with the Chrome Web Store.
Fast — compiler-level speed, not marketing:
is_official_build+ profile-guided optimization + ThinLTO + AVX2/FMA targeting- V8 pointer compression and sandbox pinned in the build config
- No telemetry subsystems competing for cycles
Memory-smart — reclaim RAM without weakening protections:
- Memory Saver on by default: background tabs discard after hours of disuse
- Windows commit-limit discarding: tabs discard before out-of-memory crashes
- Tab freezing with renderer memory purge under pressure
- Site isolation, MiraclePtr, and the spare renderer deliberately kept — memory wins come from the discard/freeze stack, never from weakened security
Private by default:
- Zero telemetry: no UMA metrics, no crash uploads, no field trials/variations, no RLZ (compiled out), no promo services — verified each release with an idle network capture
- Third-party cookies blocked by default; WebRTC never exposes local IPs
- No hyperlink auditing, no autofill crowdsourcing, no Google time queries; battery API returns constants; sensors and idle detection blocked by default
- DuckDuckGo as default search (switch to anything in two clicks)
- No Google API keys shipped — we refuse to bundle Google's shared dev key
Secure and honest about it:
- HTTPS-First mode (balanced) on by default
- Tracks Chromium stable security releases with a published patch-lag SLO (SECURITY.md)
- Windows download quarantine (Mark-of-the-Web) kept — we exclude upstream patches that disable it, along with silent-flag-injection and FTP patches
- Staged hardening lane: network-service sandbox, renderer AppContainer, extension content verification, App-Bound Encryption
Practical:
- Chrome Web Store works natively — install and auto-update extensions exactly like Chrome; uBlock Origin preinstalled on new profiles (from the store, not bundled; uninstall sticks)
- Manifest V2 runtime kept alive (sideloaded MV2 extensions keep working)
- Portable zip + installer; portable profiles supported
- No Google account Sync — Google closed Sync to all third-party Chromium builds in 2021. No fork can fix this.
- Not a vendor browser — one maintainer, measured patch delay, no fuzzing fleet. If your threat model includes targeted attackers, use Chrome or Edge. Read SECURITY.md before trusting this browser.
- Safe Browsing is inert in distributed builds (requires a non-redistributable Google key). Windows SmartScreen + uBlock Origin are the practical protection layer.
- No relation to "NAT Slipstreaming," the 2020 browser attack technique — or to slipstreaming Windows ISOs, the VPN, the racing game, or the airline logbook extension. Crowded word, empty niche.
A thin, auditable delta — no vendored Chromium, no fork of Thorium:
pinned Chromium tag -> Thorium patch series (minus our exclusions)
-> Slipstream overlay (branding, install identity)
-> Slipstream stage-90 patches (debloat/privacy/memory/security)
Every excluded upstream patch and every added patch is documented with rationale: DECISIONS.md · PILLARS.md · DEBLOAT.md. Build it yourself: BUILDING-WINDOWS.md.
| Slipstream | Chrome | Thorium | ungoogled-chromium | |
|---|---|---|---|---|
| Compiler optimizations (AVX2/PGO/LTO) | ✅ | ❌ | ✅ | ❌ |
| Zero telemetry, verified per release | ✅ | ❌ | partial | ✅ |
| Chrome Web Store + extension auto-update | ✅ | ✅ | ✅ | ❌ (workarounds) |
| Memory Saver + commit-limit discard defaults | ✅ | opt-in | ❌ | ❌ |
| Google Sync | ❌ | ✅ | ❌ | ❌ |
| Sub-24h security response | ❌ (7-day SLO) | ✅ | irregular | irregular |
| Download quarantine (MotW) kept | ✅ | ✅ | ❌ | ✅ |
| Ships Google API keys | ❌ | n/a | ❌ |
BSD-3-Clause for the Slipstream delta; Chromium and Thorium are BSD-3-Clause.
See LICENSE, TRADEMARK.md, LICENSES/.
Built on Chromium (The Chromium Authors) and the Thorium patch set
(Alexander Frick and contributors). Neither endorses this project.