chrome_page_load_script_hotspots
Identifies and ranks JavaScript script groups on the main thread that impact page load performance, such as First Contentful Paint (FCP). Use to pinpoint scripts causing slowdowns and expand slices for deeper analysis.
Instructions
Rank renderer main-thread script groups in a Chrome page-load/raw window: URL/name/process/thread/machine_id, wall/CPU totals, style/layout ms, example_slice_id. Read-only.
Use when: slow FCP/load needs post-resource JS attribution; expand example_slice_id with slice_descendants_breakdown.
Parameters: optional process filters (process_name/pid/machine_id/upid), page-load/window filters shared with chrome_main_thread_hotspots, min_total_ms (default 20), limit, max_string_len. Empty result: no matching script groups.
Input Schema
| Name | Required | Description | Default |
|---|---|---|---|
| end_ts_ns | No | Optional raw trace timestamp upper bound in nanoseconds, exclusive. This uses the same unit as trace `slice.ts`. ANDs with any page-load window. | |
| limit | No | Optional max rows to return. Defaults to 100 and is capped at 5000. Must be > 0 when set. | |
| machine_id | No | Optional machine id filter for multi-machine traces when the trace schema has `process.machine_id`. Accepts numbers and numeric strings. | |
| max_string_len | No | Optional per-string-cell character cap applied to returned rows only. Unset preserves full strings for precision; accepts both numbers and numeric strings. Must be > 0 when set. | |
| min_total_ms | No | Optional minimum aggregated wall time per grouped script hotspot. Defaults to 20 ms. Pass 0 to see every matching group. | |
| navigation_id | No | Optional Chrome navigation id used to scope scripts to one navigation phase. Matches `chrome_page_loads.navigation_id`. Mutually exclusive with `page_load_id`. If set without `phase`, defaults to `navigation_to_fcp`. | |
| page_load_id | No | Optional page-load id used to scope scripts to one navigation phase. Matches `chrome_page_loads.id`. Mutually exclusive with `navigation_id`. If set without `phase`, defaults to `navigation_to_fcp`. | |
| phase | No | Optional page-load phase window. If set without `page_load_id` or `navigation_id`, uses the latest page load in the trace. Values: navigation_to_fcp, navigation_to_load, dcl_to_fcp, fcp_to_load. | |
| pid | No | Optional OS pid filter. Accepts both numbers and numeric strings. | |
| process_name | No | Optional process-name filter (e.g. "Renderer"). Useful to scope one process type without picking a specific instance. | |
| start_ts_ns | No | Optional raw trace timestamp lower bound in nanoseconds. This uses the same unit as trace `slice.ts`. ANDs with any page-load window. | |
| upid | No | Optional trace-internal upid filter. Prefer this when distinguishing same-named Renderer processes. Accepts numbers and numeric strings. |