Mobile speed leaderboard

Slow Scans Leaderboard

Real Lighthouse scans, ranked by mobile performance score — worst first. These are the sites that treat every visitor like they have all the time in the world… or have no awareness of just how slow their own website really is.

Slow websites quietly sabotage search rankings, and potential customers go elsewhere after a 4-second load time. Think about it. Maybe it's not your fault, but the good news is we can help!

Scan your site Why it matters
Boardroom of executives waiting while a slow corporate website loads on a phone
Every spinning wheel is a stakeholder checking their watch, a deal cooling off, and a Google bot quietly downgrading you. Slow sites don't just lose visitors — they lose rooms full of them.

This Month's Bottom 10

Ranked by mobile Performance score (lower is worse). Most recent scan per domain. See yours here? Request removal

Updated Apr 19, 2026

  1. #1
    ibm.com

    Scanned 3 hours ago

    26
    Mobile
    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
  2. #2
    cisco.com

    Scanned 25 minutes ago

    37
    Mobile
    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

Feel it for yourself

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.

Own one of these domains?

If you’d rather not display your results on this list, feel free to submit a quick request for assistance.

If you’re the owner and need help with your scores, we can help — or we can just remove you from this list. Your choice.

Want the numbers fixed instead of hidden? Start a free scan and we’ll walk you through what to tackle first. Prefer to just disappear from the list? The form below does that.

Why mobile performance matters

More than half of web traffic comes from phones. Those phones run on cellular networks that are slower, spottier, and more expensive than the fiber connection your developer tested on. A site that loads in under a second on a MacBook can take twelve seconds on a mid-tier Android phone sitting in a parking lot in Dallas.

Google knows this. So do your visitors. A one-second delay in mobile load time cuts conversions by around 20%, and bounce rates triple when pages take longer than three seconds. Mobile performance is not a nice-to-have — it is the line between a website that earns trust and one that gets tapped away.

Lighthouse, the tool powering this leaderboard, scores pages against the same Core Web Vitals that feed into Google's ranking algorithm: Largest Contentful Paint (LCP), Total Blocking Time (TBT), and Cumulative Layout Shift (CLS). When a site scores below 50 on mobile, those three metrics are usually flashing red together.

How to fix a slow site

Compress images

Serve modern formats like WebP and AVIF, size them for the viewport, and lazy-load anything below the fold.

Trim the JavaScript

Third-party tag soup is the usual TBT culprit. Audit tracking pixels, defer non-critical scripts, and remove plugins you do not use.

Put it on a CDN

Edge caching cuts latency for every visitor. Cloudflare's free tier alone can slice LCP by 40% on a slow host.

Lock down layout

Reserve space for images, ads, and embeds before they load. A stable layout kills CLS and keeps visitors from tapping the wrong button.

Frequently asked questions

How are sites ranked on this leaderboard?

Sites are ranked by their most recent mobile Lighthouse Performance score within a rolling 30-day window. 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. 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.

Scan your site