Quanta presents several performance metrics, this page presents them very briefly. Clicking on each will take you to a page with more details on the metric.
Hero Time is a measure unique to Quanta. It does not exist anywhere else. It is the time that the Quanta probe will take between the start of the interaction and the moment when the success check occurs (e.g. the page is loaded, the pop-up for cookies is displayed, etc.)
The improvement in this metric means that interactivity is better: clicks produce results on the page faster.
When the user requests the page from the website, he has to wait a certain amount of time before receiving the answer: his request crosses the internet, the server receives it, checks it, creates the page, and then the page crosses the internet again in the other direction. The TTFB measures the time it takes to receive the very first byte of the response.
Meanwhile, the page is blank. Improving TTFB means that the page will display faster and will improve all other performance metrics.
The Speed Index is a score that evaluates the speed at which the web page is filled. A web page that displays in 5s while remaining completely blank for 4s will have a worse Speed Index than a web page that also displays in 5s but starts displaying elements from the first second.
The Speed Index is a complex indicator. It is expressed in seconds but it is more of a score than a measure of time. Improving it means that the impression of display speed is better for the user.
Onload is when the page has finished loading.
A long Onload means that the page is potentially too heavy or complex.
The LCP measures when the most visually impactful element is displayed. This can be an image or text. On the homepage of an ecommerce site, this is usually the main banner. On the product page of an ecommerce site, this is usually the product image.
The LCP is a "Core Web Vitals", i.e. one of the performance indicators monitored by Google to evaluate performance. By improving it, the impression of display speed improves as well as the SEO.
Total Blocking Time quantifies how unusable a page is before it is stable and fluid.
When a web page loads, many files are read and interpreted by the browser. These loads can be blocking (i.e. the user cannot interact with the page during this time AND can perceive it). The TBT measures the accumulation of all these blockages between the moment when the first visual element is displayed, and the moment when the page becomes fully interactive.
Improving it ensures that the page is usable, even before it is fully loaded.