What is measured
JPEG, PNG, WebP and AVIF cases record output bytes, wall-clock duration, successful re-decode and final dimensions. Each case gets one unmeasured warm-up followed by three measured sequential trials.
What timing includes
Duration starts before the job enters the worker and ends when the encoded result returns. It includes worker messaging, source decode, canvas transforms and encoding. Re-decode verification happens afterward and is recorded separately.
Fair comparisons
Use a fixed, redistributable corpus covering photos, UI screenshots, line art, gradients and transparent images. Keep source hashes unchanged between devices. Equal nominal quality settings are not equivalent perceptual quality, so quality-target comparisons must be reported separately.
Every result carries context
Raw runs include source hashes, dimensions, browser identity, platform, hardware hints, exact settings, trial counts, failures and known limitations. The runner validates its output against the versioned contract before download.
What we will not claim
A result from one corpus, browser or device is not a universal truth. Unsupported combinations are marked with a reason instead of being hidden or treated as zero.