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Long Main Thread Tasks

Priority: Critical

Impact: Negative

What issues it may causeโ€‹

  • Delayed Interactivity: Long tasks can delay the responsiveness of a webpage, making interactions feel sluggish and unresponsive to users.

  • Poor User Experience: Lengthy processing times can frustrate users, leading to higher bounce rates and lower engagement.

  • Reduced Performance: Long tasks can significantly impact overall page performance, affecting metrics such as time to interactive and first input delay.

How do you fix itโ€‹

  • Optimize JavaScript: Long scripts are often a cause of long tasks. Identify and refactor complex or inefficient JavaScript code to reduce execution times.

  • Minimize Render-Blocking Operations: Optimize rendering processes to prevent long tasks from blocking critical rendering tasks.

  • Use Web Workers: Offload heavy computation to web workers to run scripts concurrently, reducing the impact on the main thread.

Learn more about optimizing long tasks.

What is the positive impactโ€‹

  • Improved Responsiveness: Mitigating long tasks enhances the responsiveness of the webpage, providing users with a smoother browsing experience.

  • Enhanced User Satisfaction: Faster page responsiveness contributes to higher user satisfaction and engagement metrics.

  • Better Performance Metrics: Addressing long tasks positively impacts performance metrics such as time to interactive, ultimately leading to better overall website performance.

How to fetch the data for this report templateโ€‹

You will need to run a crawl for report template to generate report. When report has been generated and you have crawl id you can fetch data for the report using the following query:

query GetReportForCrawl($crawlId: ObjectID!, $reportTemplateCode: String!) {
getCrawl(id: $crawlId) {
input: {
reportTypeCodes: Basic
reportTemplateCodes: [$reportTemplateCode]
) {
rows {
nodes {
... on CrawlSiteSpeedAuditOpportunities {

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