Mobile speed leaderboard
Slow Scans Leaderboard — 2 Sites Scoring 65 or Lower
Only domains scoring 65 or lower will make the cut. A website that treats every visitor like they have all the time in the world or perhaps lack the awareness of how slow their own website really is for mobile users. These are Google Lighthouse scans, ranked by the slowest mobile performance score.
Slow websites quietly sabotage search rankings while potential customers go elsewhere after a four second load time. Think about it. Maybe it is not your fault. The good news is we can help.
This Month’s Lowest Performers
Ranked by mobile Performance score (lower is worse), 65 or under only. Most recent scan per domain. See yours here? Request removal
Updated Apr 27, 2026
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26—
- LCP Largest Contentful Paint. Time until the biggest visible element (hero image, headline) finishes loading. Under 2.5s is good; over 4s is poor.
- 28.2s
- TBT Total Blocking Time. How long the browser was frozen by heavy JavaScript while loading. Under 0.2s is good; over 0.6s is poor.
- 2.5s
- CLS Cumulative Layout Shift. How much the page jumps around while loading. Under 0.1 is good; over 0.25 is poor.
- 0.060
1 week ago -
37—
- LCP Largest Contentful Paint. Time until the biggest visible element (hero image, headline) finishes loading. Under 2.5s is good; over 4s is poor.
- 5.2s
- TBT Total Blocking Time. How long the browser was frozen by heavy JavaScript while loading. Under 0.2s is good; over 0.6s is poor.
- 2.6s
- CLS Cumulative Layout Shift. How much the page jumps around while loading. Under 0.1 is good; over 0.25 is poor.
- 0.028
1 week ago
Feel the delay of ibm.com
Pick a site from the list and watch how the same page loads across three connection speeds. The bar that finishes first is what your desktop sees; the bar that crawls is what a real mobile visitor feels.
Durations are illustrative, derived from the scan’s Largest Contentful Paint value scaled by each profile’s network characteristics. Actual page loads vary.
Why mobile performance matters
More than half of all web traffic now comes from mobile devices. Yet most websites are still tested on high-speed fiber connections in controlled environments. The reality for your visitors is very different: they’re often on slower, less reliable cellular networks, using mid-range phones in less-than-ideal conditions, whether sitting in traffic, walking through a parking lot in Dallas heat, or simply dealing with everyday signal fluctuations.
A page that loads in under a second on a desktop can easily take 10 to 12 seconds on a typical mobile device under real-world conditions. That difference matters. Google’s own research shows that even a one-second delay in mobile load time can reduce conversions by approximately 20%. When pages take longer than three seconds to load, bounce rates often triple.
Mobile performance is not a technical luxury. It’s a fundamental driver of user trust, engagement, and revenue. Visitors who experience frustration are quick to leave, and search engines notice too.
This is precisely why Lighthouse, the tool behind this performance leaderboard, evaluates sites using Google’s Core Web Vitals, the same metrics that influence search rankings:
- Largest Contentful Paint (LCP) measures how quickly the main content becomes visible.
- Total Blocking Time (TBT) captures how long the page is unresponsive to user input.
- Cumulative Layout Shift (CLS) tracks unexpected layout movements that disrupt the experience.
When a site scores below 50 on mobile, these three metrics are typically all in the red. The result? A poor user experience that hurts both conversions and visibility in search results.
The good news? These issues are fixable. With targeted optimizations, most websites can deliver a fast, smooth experience on mobile, building trust with visitors and improving performance where it counts most.
How to fix a slow site
Compress Images
Serve modern formats like WebP and AVIF, size images precisely for the viewport, and lazy-load everything below the fold. Smaller files translate to faster delivery, even on slower cellular networks, without compromising visual quality.
Trim the JavaScript
Third-party scripts and tracking tags are frequent contributors to excessive Total Blocking Time. Conduct a thorough audit, defer non-critical scripts, and remove unused plugins. This allows your page to respond quickly, so visitors can interact without frustrating delays.
Put it on a CDN
Edge caching delivers your content from servers closer to every visitor, significantly reducing latency. Even Cloudflare’s free tier can reduce Largest Contentful Paint by up to 40% on a slow host, transforming sluggish load times into smooth, responsive experiences.
Lock Down Layout
Reserve space for images, ads, and embeds before they load. A stable layout eliminates Cumulative Layout Shift, preventing unexpected jumps that frustrate users and cause accidental clicks. Your visitors remain in control and engaged with your site.
Frequently asked questions
How are sites ranked on this leaderboard?
Only domains whose most recent mobile Lighthouse Performance score lands at 65 or lower appear here. Lower scores rank worse. We break ties using Largest Contentful Paint — if two sites share the same score, the slower LCP takes the worse rank.
What counts as a "qualifying" scan?
A mobile-strategy Lighthouse scan that completed without error and produced a Performance score at or below 65. Timeouts, abandoned scans, and desktop-only runs are excluded. We also drop any scan flagged for removal by the domain owner.
What network speed is Lighthouse simulating?
Lighthouse's mobile preset throttles the connection to a simulated Slow 4G profile: roughly 1.6 Mbps down, 750 Kbps up, and 150ms round-trip latency. It also throttles CPU to approximate a mid-tier Android phone, which is why sites feel dramatically slower than they do on your laptop.
Can my site be removed from the leaderboard?
Yes. Use the Request removal form near the bottom of this page — include the domain, your email, and a brief reason. Approved requests take effect immediately and the domain is also blocked from future listings.
Does a low score mean my site is broken?
Not necessarily. A low Performance score means the site is slow on mobile connections, which hurts conversions and search rankings but does not mean it is offline. It usually points at big unoptimized images, bloated JavaScript, or a host that is far from your visitors.
How often does the leaderboard update?
Every time a new qualifying scan is logged. The leaderboard is cached at the edge for fast page loads and is invalidated automatically whenever the underlying data changes.
