Long task

A long task is a task that takes more than 50ms to complete.

It is an uninterrupted period where the {{Glossary("main thread", "main UI thread")}} is busy for 50 ms or longer. Common examples include long running event handlers, expensive {{Glossary("reflow", "reflows")}} and other re-renders, and work the browser does between different turns of the event loop that exceeds 50 ms.

See also

• Long Tasks API
• Long Animation Frames API