Why Can Several Images Compress at the Same Time?
Batch image compression starts up to 4 parallel processing units (Workers) at once rather than queuing files one at a time — the main reason batch jobs feel faster than expected.
How the parallel count is decided
The tool reads the number of logical CPU cores your device reports, and uses whichever is smaller between that number and 4 as the worker count — a device with more than 4 cores runs the full 4 parallel workers, while a dual-core device only runs 2, avoiding a pile-up of tasks competing for the same limited resources and slowing everything down.
Why video compression doesn't have this
Video transcoding is far heavier than image compression — a single video job can already occupy a substantial share of available CPU and memory. Running several transcodes in parallel would mean multiple heavy jobs competing for the same resources, usually making things slower overall rather than faster — so video compression deliberately uses a single worker with tasks strictly queued one at a time. That's a considered trade-off, not a missing feature.
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