Finding where time goes.
WHAT THE PERFORMANCE PANEL RECORDS
Everything happening over a period: scripting, rendering, layout, painting and network.
WHAT TO RECORD
The specific interaction that is slow, not the whole session.
WHY
A long recording is difficult to interpret.
WHAT TO LOOK FOR
Long tasks blocking the main thread Layout recalculated repeatedly Scripting dominating Large gaps waiting
WHAT A LONG TASK IS
Work occupying the main thread long enough to prevent response.
WHY THAT MATTERS
It is what makes an interface feel unresponsive.
WHAT TO DO ABOUT IT
Break the work up, or move it to a worker.
WHAT CAUSES REPEATED LAYOUT
Reading a layout property immediately after changing one, repeatedly.
WHAT TO DO
Read all values, then write all values.
WHAT TO ALWAYS ENABLE WHEN MEASURING
Processor throttling, simulating a slower device.
WHY
Development hardware is far faster than what most visitors use.
WHAT THE AUDITING TOOL PROVIDES
Automated assessment of performance, accessibility, best practice and search readiness.
WHAT TO TREAT IT AS
A starting list, not a target to optimise for.
