main thread
—
v153 · loaf in workers
What each thread can observe
A real worker is started, asked what its PerformanceObserver supports, and its answer is put next to the main thread's. Neither list is written into this page — both are read at load, from the browser you are using.
Supported entry types
worker
—
The lists are not sorted the same way on purpose — they are printed in the order each thread reports them, because the order is the browser's and reordering it would be editing the evidence.
The difference, type by type
| entry type | main thread | worker | what it reports |
|---|
A real long animation frame, on the main thread
If the main thread supports the type, blocking it produces a genuine entry — the thing a worker cannot produce.
| field | value |
|---|---|
| Not run yet. | |
Blocking the main thread freezes this page for a quarter of a second, on purpose. That is the point: the freeze is measurable here, and the identical freeze inside a worker is not.