Costco's website isn't structurally broken or offline for extended periods, but it does go down temporarily—usually during flash sales, holiday shopping peaks, or when they're pushing infrastructure updates. The most common culprits are traffic spikes that overwhelm their CDN or database capacity, and occasionally scheduled maintenance windows. If you're getting errors or can't load pages, first verify it's not just you. Tools like DownDetector aggregate user reports in real time and show whether others in your region are experiencing the same issue. You can also try switching networks (mobile data vs. WiFi) or clearing your browser cache, since Costco's site uses heavy client-side caching that sometimes conflicts with stale session data. Costco runs separate domains for different markets—costco.ca for Canada, costco.com for the US. If one appears down, the other might still be accessible, though product availability and pricing differ. Their infrastructure is enterprise-grade but not immune to the same load-balancing challenges we see with any high-volume ecommerce platform handling millions of SKUs and real-time inventory. From a web design perspective, Costco's site isn't optimized for resilience the way you'd expect from a tech-first company. They prioritize transaction security and inventory accuracy over uptime redundancy, which means when something breaks, it breaks visibly. At Ottawa SEO, when we build ecommerce platforms, we architect for degraded performance rather than total failure—static product pages stay up even if the cart system lags. If you're consistently unable to access Costco's site over several hours, contact their customer service directly at 1-800-463-3783 in Canada. Persistent regional outages sometimes indicate DNS propagation issues or ISP-level routing problems rather than site-wide downtime. For business users relying on Costco's B2B portal, keep a secondary procurement channel active since their uptime SLA isn't publicly guaranteed like AWS or Shopify.