You&#x27;re right. There&#x27;s enough diversity in SIMD instruction sets that no single rule seems sufficient for deciding what to include. Operations which are &quot;fast&quot; on all popular hardware are obviously great, but SIMD.js also includes some operations needed by popular use cases, such as allTrue() and anyTrue(). Also, while these operations are &quot;fast&quot; on x86 as you say, on NEON they&#x27;re at least no worse than what applications would do otherwise.