Brave Adblock Engine Rewrite Delivers 75 Percent Lower Memory Use

Brave Browser, which recently reached more than 100 million users worldwide, has rolled out a major overhaul of its built-in adblocking engine, cutting memory consumption by 75 percent and delivering a measurable performance boost across desktop and mobile platforms. The changes are live starting with Brave v1.85, with further optimizations scheduled for v1.86.

According to the Brave privacy and security team, the reworked adblock engine now saves roughly 45 MB of memory by default on all supported platforms, including Android, iOS, and desktop systems. The savings increase further for users who enable additional filter lists.

As you can expect, reduced memory usage translates directly into smoother multitasking, improved responsiveness, and better battery life, particularly on mobile devices and older hardware.

This was achieved through a series of iterative refactors to Brave’s Rust-based adblock engine. According to the devs, the most significant architectural change was migrating around 100,000 default ad-blocking filters from standard heap-allocated Rust data structures to FlatBuffers, a compact, zero-copy binary storage format.

Beyond the FlatBuffers transition, Brave implemented several targeted optimizations. Memory allocations during engine construction were reduced by 19 percent through the use of stack-allocated vectors, while build times improved by approximately 15 percent. Filter matching performance increased by 13 percent after tokenizing commonly used regular expression patterns.

On desktop systems, shared resources between adblock engine instances now save an additional 2 MB of memory, and internal resource storage was optimized to reduce memory use by 30 percent.

Brave emphasized that these deep optimizations are possible because its adblocking is native to the browser and maintained in-house by its privacy team. Unlike extension-based blockers, which are constrained by browser extension APIs and sandboxing, Brave’s integrated approach allows low-level architectural changes.

For more information, see Brave’s post.

Image credits: Brave