description YSlow Overview
YSlow is an open-source tool that analyzes website performance by measuring First Contentful Paint, Largest Contentful Paint, and Cumulative Layout Shift, providing data to identify and address potential bottlenecks impacting page load speed and user experience.
help YSlow FAQ
How good is YSlow?
YSlow scores 5.43/10 (Mediocre) on Lunoo, making it rated in the WebPageTest category.
What are the best alternatives to YSlow?
See our alternatives page for YSlow for a ranked list with scores. Top alternatives include: http_load, Pylot, Site Relic.
How does YSlow compare to http_load?
See our detailed comparison of YSlow vs http_load with scores, features, and an AI-powered verdict.
Is YSlow worth it in 2026?
With a score of 5.43/10, YSlow is a solid option in WebPageTest. See all WebPageTest ranked.
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