Performance Budgets & Alerts
A performance budget is a threshold a metric should stay under. In LoadFocus your budgets are the threshold alerts on a monitor: every result is checked against them, the history charts draw them, and a CI pipeline can fail a build on them. LoadFocus comes with recommended budgets to start from.
Recommended budgets
These are the budgets LoadFocus uses out of the box. They are the same for mobile and desktop monitors:
| Metric | Recommended budget |
|---|---|
| Largest Contentful Paint (LCP) | 2.5 s |
| Total Blocking Time (TBT) | 200 ms |
| Cumulative Layout Shift (CLS) | 0.1 |
| First Contentful Paint (FCP) | 1.8 s |
| Speed Index | 3.4 s |
| Server Response Time (TTFB) | 0.8 s |
| Time to Interactive | 3.8 s |
| Performance score | 90 |
See your budget on the result
Every lab metric gauge (First Contentful Paint, Speed Index, Server Response Time (TTFB), Largest Contentful Paint, Total Blocking Time and Cumulative Layout Shift) shows a target such as "Budget: 2.5 sec" under the value, so you see the target right next to the measurement.
The Budgets section of a result
Every enabled alert on the monitor with above or below and a value is a budget. The Budgets section of each result checks that run against all of them:
- Each budget shows the measured value, the limit and Within budget, Over budget or Not measured.
- The line above the list says how many budgets the run met or exceeded.
- Manage alerts opens the monitor's alerts, where you add, change or remove budgets.
The history charts for First Contentful Paint, Largest Contentful Paint, Speed Index, Total Blocking Time and Cumulative Layout Shift draw each budget as a dashed line and name it in the chart title (for example "Budget 2.5 s"), so you can see when a metric crossed it. Alerts that use "regresses by (%)" and alerts on real-user field metrics have no fixed lab limit, so they are not shown as budgets.
Besides the scores and lab metrics, you can set a budget on Page Weight (KB) and Requests. When you pick one of them in the alert form, it starts at 2000 KB and 80 requests, and you can change the value.
To fail a build when a budget breaks, see CI build gating.
One-click Core Web Vitals budget alerts
On the New Alert page, pick a monitor and click "Add Core Web Vitals budget alerts". It creates LCP, TBT and CLS alerts at the recommended budgets in one click, skipping any metric that already has an alert. These alerts notify you when the budget is missed and again when the metric recovers, not on every run.
How budget alerts fire
When you pick a lab metric in the alert form, the recommended threshold pre-fills if the value box is empty, and you can change it. For a manual alert you choose how often it notifies you.