The read-only detail property returns arbitrary metadata that was included in the mark upon construction (when using performance.measure().

Returns the value it was set to (from markOptions of performance.measure()).

The following example demonstrates the detail property.

performance.measure("dog", { detail: "labrador", start: 0, end: 12345 });

const dogEntries = performance.getEntriesByName("dog");

dogEntries[0].detail; // labrador