| Core Rendering Engine | Gecko is a standalone engine with its own DOM, CSS, layout, and painting pipeline, independent of WebKit. It emphasizes long-term standards compliance and modularity, with many subsystems rewritten or modernized under the Quantum initiative. | Blink is a WebKit fork tightly coupled with Chromium’s compositor, GPU process, and multi-process architecture. It prioritizes throughput, site isolation, and rapid feature rollout driven by Chrome’s release cadence. |
| CSS Style Engine | Stylo, derived from the Servo project and written largely in Rust, performs parallel CSS style computation across multiple CPU cores, using safe concurrency guarantees to avoid data races and memory corruption. | Blink CSS engine is written in C++ and uses task-based parallelism but remains more tightly bound to the main rendering and compositor threads, with fewer safety guarantees but highly optimized hot paths. |
| JavaScript Engine | SpiderMonkey focuses on predictable performance, incremental and compacting garbage collection, and detailed memory accounting, which is particularly beneficial on memory-constrained Linux and embedded systems. | V8 emphasizes aggressive JIT compilation, speculative optimization, and peak JavaScript execution speed, often outperforming SpiderMonkey in compute-heavy JS workloads at the cost of higher memory usage. |
| Process Model | Uses a configurable multi-process model (Electrolysis) where content processes can be tuned to balance memory usage and responsiveness. Historically more flexible and less aggressive than Chromium’s model. | Uses a strict multi-process, site-isolation-first model where each site instance typically runs in its own renderer process, improving security but significantly increasing baseline memory consumption. |
| GPU Architecture | WebRender is a retained-mode GPU compositor that builds a scene graph and submits GPU-friendly batches, minimizing CPU involvement during scrolling, animations, and transforms. | Uses a tile-based rendering model where content is rasterized into tiles and composited by the Viz display compositor, with heavy reliance on GPU process scheduling and buffer management. |
| Graphics API Usage | Primarily uses OpenGL via EGL on Linux, with growing Vulkan support for WebRender, especially important for modern Wayland compositors and future GPU backends. | Uses ANGLE as an abstraction layer, translating OpenGL ES calls to Vulkan, OpenGL, or other backends, improving portability but adding an extra translation layer. |
| Vulkan Support | Native Vulkan backend in WebRender is actively developed and increasingly used on Linux, especially for Wayland and next-generation GPU drivers. | Vulkan support is indirect via ANGLE, meaning Vulkan is often used as a translation target rather than a first-class rendering API. |
| Wayland Support | Mature, native Wayland backend with direct integration into GNOME and KDE compositors, enabling better frame timing, lower latency, and reduced reliance on XWayland. | Wayland support is functional but historically experimental, enabled via Ozone and feature flags, and still less stable on some distributions and GPU drivers. |
| X11 Support | Fully supported, though considered legacy compared to Wayland; still stable and widely used on older Linux desktops and remote environments. | Fully supported and historically more stable than its Wayland backend, often preferred in enterprise and legacy setups. |
| GPU Process Isolation | GPU work is tightly integrated with the main browser architecture but still sandboxed, with fewer processes involved compared to Chromium. | Dedicated GPU process is strictly sandboxed and isolated, improving fault tolerance but increasing IPC overhead and complexity. |
| Hardware Video Decode Framework | Relies on GStreamer, integrating deeply with the Linux multimedia stack and allowing use of system-provided codecs and hardware acceleration APIs. | Uses a custom media pipeline with limited system integration; hardware decoding is often restricted by build flags, codec licensing, and distribution policies. |
| VA-API Video Decode | Supported on Linux for H.264, VP8, VP9, and AV1 depending on driver and codec availability, with relatively straightforward enablement. | VA-API support is inconsistent across distributions and often disabled by default; may require patched builds or runtime flags to function reliably. |
| VDPAU Support | Indirectly supported via GStreamer plugins, depending on GPU driver capabilities. | Limited and inconsistent; often relies on VA-API translation layers rather than native VDPAU paths. |
| Hardware Video Encode | Supported through GStreamer when underlying drivers provide encode capabilities, though less commonly used by web applications. | Encode support exists but is more tightly controlled and less exposed to the web platform. |
| WebGL Implementation | Uses native OpenGL ES or desktop OpenGL directly through the graphics stack, with fewer abstraction layers between WebGL and the driver. | WebGL calls typically pass through ANGLE, which translates them to the underlying graphics API, improving consistency but potentially affecting performance or debuggability. |
| WebGPU Status | Actively developing native WebGPU support with Vulkan as a primary backend on Linux. | WebGPU support is more mature in terms of feature exposure but often relies on abstraction layers and experimental flags. |
| Compositor Thread Model | WebRender runs largely independently of the main thread once a scene is built, reducing jank during scrolling and animations. | Viz compositor operates with tight coordination between renderer, GPU, and browser processes, which can introduce overhead but improves isolation. |
| Memory Footprint | Lower baseline memory usage due to fewer processes and more shared infrastructure, particularly noticeable on low-RAM systems. | Higher baseline memory usage due to per-site renderer processes and duplicated JIT and heap structures. |
| Memory Debugging | Exposes detailed, fine-grained memory reporting via built-in tools, making it easier to diagnose leaks and fragmentation on Linux. | Provides powerful tracing tools but they are less accessible and more complex for routine debugging. |
| Sandbox Implementation | Uses Linux namespaces and seccomp-bpf with configurable strictness to balance security and compatibility across diverse Linux environments. | Uses one of the most restrictive sandboxes on Linux, heavily relying on namespaces, seccomp-bpf, and broker processes. |
| Embedded Linux Suitability | Often preferred for embedded and non-mainstream architectures due to reliance on system libraries and openness to customization. | More challenging to port and maintain on embedded platforms due to size, dependency complexity, and build-time assumptions. |
| RISC-V Enablement | Community-driven support with increasing upstream work, benefiting from simpler graphics and media integration paths. | Experimental and less mature, with many acceleration features unavailable or disabled on RISC-V. |
| Debugging GPU Issues | Easier to trace GPU and EGL issues due to fewer abstraction layers and clearer logging paths. | GPU debugging can be complex due to ANGLE, GPU process isolation, and multiple IPC layers. |
| Update and Patch Model | Slower but more controlled, with emphasis on stability and long-term maintainability. | Faster and more aggressive, with frequent changes that can impact downstream Linux distributions. |
