Why Chrome 91’s WebAssembly SIMD Is a Game-Changer for Web Performance

Background

For over a decade, web technology has advanced rapidly, with Chrome playing a pivotal role; understanding Chrome helps grasp industry trends.

TL;DR

What is Chrome 91’s biggest highlight? WebAssembly SIMD

Release date: 2021-05-25

Number of new features: 18 (see Chrome Platform Status)

V8 engine version: v9.1

Other interesting features listed below

Detailed Analysis

WebAssembly SIMD

Chrome 91 enables WebAssembly SIMD by default.

SIMD (Single Instruction Multiple Data) allows a single instruction to process multiple data elements simultaneously.

It provides data‑level parallelism; for example, adding two length‑4 arrays can be done with one vector addition instead of four scalar adds.

SIMD is widely used in video, audio, image processing, encryption, animation, games, and AI, boosting performance of vector data. Major CPUs support SIMD (e.g., x86 SSE, ARM Neon).

WebAssembly SIMD adds a new v128 type and related operators, representing 128‑bit vectors.

WebAssembly SIMD implements a subset of the most common SIMD instructions across CPUs, abstracting them so developers only need to learn WebAssembly SIMD.

Current toolchains (e.g., Emscripten) compile WebAssembly SIMD to x86 SSE/AVX and ARM Neon.

WebAssembly SIMD is in Phase 4 of the WebAssembly proposal process and is already implemented in V8 (Chrome, Node.js), Firefox, and Emscripten.

In gesture‑recognition demos, SIMD significantly improves frame rates and smoothness.

TensorFlow.js 2.1.0 supports WebAssembly SIMD; face‑detection (BlazeFace) runs 1.7‑2.1× faster.

For heavier AI workloads like ImageNet, MobileNet V2 gains 2.2‑4.5× speedup.

WebSockets over HTTP/2

Chrome 91 adds support for WebSockets over HTTP/2.

Traditional WebSockets use a separate TCP connection (HTTP/1.1), which wastes resources. Over HTTP/2 they can share the same multiplexed connection, reducing overhead.

Block HTTP port 10080

To mitigate the NAT Slipstream 2.0 attack, Chrome 91 blocks port 10080, adding to previously blocked ports.

Accessing blocked ports yields ERR_UNSAFE_PORT.

GravitySensor API

Chrome 91 introduces the GravitySensor API to obtain device acceleration caused by Earth’s gravity, useful for games such as tilt‑controlled racing, a feature requested by Unity developers.

Conclusion

The biggest highlight of Chrome 91 is WebAssembly SIMD, which expands the performance envelope of web applications across video, audio, image, encryption, animation, gaming, and AI. Continued innovations like SIMD will keep the web evolving and enable richer, faster experiences in the coming decade.