Troubleshooting a slow website·续

Cache additional static content

By default, Cloudflare only caches certain file extensions. To cache additional static content:

  1. Go to Caching > Cache Rules.
  2. Create a rule to cache specific content.
  3. Set appropriate Edge TTLs.

Caution

Be careful when caching HTML or API responses. These often contain personalized or dynamic content that should not be cached. Only cache content you are certain is static.

Use Cloudflare Trace to debug cache rules

If your cache rules are not applying as expected, use Cloudflare Trace to simulate a request and see exactly which rules match. Trace shows you how your Cloudflare configurations (including cache rules, page rules, and other settings) would affect a specific URL.

This is particularly useful when:

  • A cache rule should be caching content but the response shows DYNAMIC or BYPASS
  • You are unsure which rule is taking precedence
  • You want to test a "what-if" scenario before making changes

Step 6: Diagnose network issues

If curl shows high TCP Connect or TLS Handshake times, the issue may be network-related rather than application-related.

Test your Internet connection

Visit speed.cloudflare.com ↗︎ to test:

  • Download and upload speeds
  • Latency (ping)
  • Jitter
  • Packet loss

Poor results indicate issues with your local network or ISP.

Run MTR from your location to Cloudflare

MTR combines traceroute and ping to show latency and packet loss at each network hop.

mtr -rw www.example.com

Download WinMTR ↗︎ and run it with your domain as the target.

Look for:

  • High latency at specific hops (indicates slow network segments)
  • Packet loss (indicates network congestion or issues)
  • Timeouts (may indicate firewalls or routing issues)

For more details, refer to How to read MTR ↗︎.

Run MTR from your origin to Cloudflare

If you have access to your origin server, run MTR from the origin to a Cloudflare IP address ↗︎ to test the network path between your origin and Cloudflare.

mtr -rw 104.16.132.229

High latency or packet loss on this path affects all requests that miss the cache.

Step 7: Understand network routing

How requests are routed to Cloudflare data centers can significantly impact performance.

Identify which data center serves your requests

Add /cdn-cgi/trace to your domain to see which Cloudflare data center is serving your requests:

curl https://www.example.com/cdn-cgi/trace

Invoke-RestMethod -Uri "https://www.example.com/cdn-cgi/trace"

The colo field shows the three-letter airport code of the serving data center (for example, colo=SJC for San Jose). You can find the full list of Cloudflare data centers and their codes on the Cloudflare status page ↗︎.

Why routing matters

When a request reaches Cloudflare:

  1. The request is routed to a nearby Cloudflare data center based on anycast routing ↗︎.
  2. If the content is cached, it is served immediately.
  3. If not cached, Cloudflare fetches from your origin server.

If your origin server is geographically distant from the Cloudflare data center serving your users, uncached requests will be slow.

Troubleshoot unexpected routing

If requests are being routed to a data center that seems far from the user, this may be due to Cloudflare's automated traffic engineering or a user’s ISP routing traffic.

While Cloudflare always strives to provide the best possible performance by serving traffic from the closest location, reliability is the top priority. In instances where performance and reliability are in conflict, Cloudflare's systems are designed to prioritize a stable connection over a local one.

For more details, refer to Cloudflare traffic not being sent to the geographically closest data center.

Common causes of unexpected routing:

Symptom Explanation
Requests route to a distant data center Cloudflare traffic engineering for reliability, or ISP routing decisions
Routing changes between requests Normal behavior - routing adapts to network conditions or ISP load balancing
Consistent routing to a distant region ISP peering location or Cloudflare capacity management
High latency despite nearby data center Network congestion on the path

Solutions for origin distance

Consider these solutions based on your needs:

Solution Description Best for
Improve cache hit ratio Cache more content to reduce origin fetches All sites
Tiered Cache Use upper-tier data centers to reduce origin requests Sites with global traffic
Argo Smart Routing Route traffic over faster network paths Sites with slow origin connections
Move origin closer Deploy origin servers in multiple regions Large-scale applications

Enable Argo Smart Routing

Argo Smart Routing analyzes network conditions in real-time and routes traffic over the fastest paths, reducing latency by an average of 30%.

Argo Smart Routing is part of Smart Shield, which bundles multiple Cloudflare performance and reliability features.

To enable Argo Smart Routing:

  1. Go to the Cloudflare dashboard ↗︎.
  2. Follow the Smart Shield setup guide to enable the feature.

Argo is particularly effective when:

  • Your origin is far from your users
  • Network congestion affects certain paths
  • You need consistent performance globally

For detailed information about how Argo Smart Routing works, refer to the Argo Smart Routing documentation.

Contact Support if the problem persists

If you have followed the steps above and the performance issue persists, contact Cloudflare Support for assistance.

When contacting Support, provide as much evidence as possible to help diagnose the issue:

  • HAR file - Generate a HAR file that captures the slow requests. This provides detailed timing information for every request.
  • Observatory results - Share screenshots or links to your Observatory test results.
  • RUM data - If you have Web Analytics enabled, share relevant metrics showing the performance issue.
  • curl output - Include the timing breakdown from curl --write-out for the slow assets.
  • MTR results - If you suspect network issues, include MTR output from your location to the affected domain.
  • Specific URLs - List the exact URLs that are slow, along with the expected and actual response times.

The more evidence you provide showing the slowness, the faster Support can identify and resolve the issue.

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