--- title: "What is Long Tasks? Definition & Meaning" description: "A long task is any task that occupies the browser main thread for more than 50 milliseconds, blocking it from responding to user input or rendering updates..." lang: en json-ld: | [ { "@context": "https://schema.org", "@type": "DefinedTerm", "name": "Long Tasks", "description": "A long task is any task that occupies the browser main thread for more than 50 milliseconds, blocking it from responding to user input or rendering updates during that period.", "url": "https://www.pagespeedmatters.com/resources/glossary/long-tasks", "inDefinedTermSet": { "@type": "DefinedTermSet", "name": "Web Performance Glossary", "url": "https://www.pagespeedmatters.com/resources/glossary" } }, { "@context": "https://schema.org", "@type": "BreadcrumbList", "itemListElement": [ { "@type": "ListItem", "position": 1, "name": "Home", "item": "https://www.pagespeedmatters.com" }, { "@type": "ListItem", "position": 2, "name": "Resources", "item": 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Squarespace Speed Optimization ](/services/squarespace-speed-optimization) [Book a Call](/contact) [Home](/) [Resources](/resources) [Glossary](/resources/glossary) Long Tasks Interactivity & Rendering · Glossary # Long Tasks ![Matt Suffoletto](/assets/matt-CEkmAuBN.jpg)Written by [Matt Suffoletto](/resources/author/matt-suffoletto) Published June 26, 2026 ![Long Tasks](/__l5e/assets-v1/d7fefe04-c9c5-40d8-a41c-0070aa05c7a1/gloss-hero-long-tasks.png) Share [](https://twitter.com/intent/tweet?url=https%3A%2F%2Fwww.pagespeedmatters.com%2Fresources%2Fglossary%2Flong-tasks&text=Long%20Tasks)[](https://www.facebook.com/sharer/sharer.php?u=https%3A%2F%2Fwww.pagespeedmatters.com%2Fresources%2Fglossary%2Flong-tasks)[](https://www.linkedin.com/sharing/share-offsite/?url=https%3A%2F%2Fwww.pagespeedmatters.com%2Fresources%2Fglossary%2Flong-tasks)[](https://www.reddit.com/submit?url=https%3A%2F%2Fwww.pagespeedmatters.com%2Fresources%2Fglossary%2Flong-tasks&title=Long%20Tasks) On This Page - [TL;DR](#tldr "TL;DR") - [What is Long Tasks](#definition "What is Long Tasks") - [How It's Measured](#how-measured "How It's Measured") Share this guide [](https://twitter.com/intent/tweet?url=https%3A%2F%2Fwww.pagespeedmatters.com%2Fresources%2Fglossary%2Flong-tasks&text=Long%20Tasks)[](https://www.facebook.com/sharer/sharer.php?u=https%3A%2F%2Fwww.pagespeedmatters.com%2Fresources%2Fglossary%2Flong-tasks)[](https://www.linkedin.com/sharing/share-offsite/?url=https%3A%2F%2Fwww.pagespeedmatters.com%2Fresources%2Fglossary%2Flong-tasks)[](https://www.reddit.com/submit?url=https%3A%2F%2Fwww.pagespeedmatters.com%2Fresources%2Fglossary%2Flong-tasks&title=Long%20Tasks) Speed Audit ### Find out what's slowing your website down Enter your URL and our team will send back a free, no-strings performance analysis within 24 hours. Get my audit 100% free Results in 24h ## TL;DR A long task is any task that occupies the browser main thread for more than 50 milliseconds, blocking it from responding to user input or rendering updates during that period. ## What is Long Tasks? A long task is any task that occupies the browser main thread for more than 50 milliseconds, blocking it from responding to user input or rendering updates during that period. Learn more in our [how to improve long tasks](/resources/guides/web-performance-optimization-complete-guide) guide, or work with us through our [done-for-you speed optimization service](/services/core-web-vitals-optimization). ## How Long Tasks is Measured Long tasks are reported by the Long Tasks API and visible in the Performance panel of Chrome DevTools and in Lighthouse. ## Related Terms [Glossary ### Main Thread Work ](/resources/glossary/main-thread-work)[Glossary ### Total Blocking Time (TBT) ](/resources/glossary/total-blocking-time)[Glossary ### Interaction to Next Paint (INP) ](/resources/glossary/interaction-to-next-paint) Sources - [web.dev: Long tasks](https://web.dev/articles/long-tasks-devtools) [![PageSpeed Matters](/assets/logo-DtyG_mQE.png)](/) We optimize website load times to rank higher, decrease advertising costs, and convert more often. 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