Cloudflare, one of the world’s biggest internet infrastructure companies, faced a massive global outage on November 18, 2025, bringing significant parts of the internet to a halt for several hours. The disruption affected major platforms, public services, AI tools, and millions of websites that rely on Cloudflare’s Content Delivery Network (CDN), DNS, and security systems.

This report breaks down the incident from the basics—what Cloudflare does, what caused the failure, how it impacted global services, and how the company resolved it.

What Is Cloudflare and Why It Matters

Cloudflare operates a global network of servers that sit between users and websites. Acting as a “reverse proxy,” it handles traffic, speeds up loading, blocks cyberattacks, and manages DNS services for millions of domains worldwide.

Core Functions of Cloudflare

• CDN (Content Delivery Network): Caches website content on global edge servers, reducing load time.
• DNS Hosting: Provides fast, secure DNS lookups.
• DDoS Protection: Detects and absorbs traffic floods.
• WAF (Web Application Firewall): Blocks malicious requests.
• SSL/TLS Encryption: Enables secure HTTPS connections.

Because so many organizations depend on Cloudflare for performance and security, any major failure impacts the internet at scale.

Overview of the Outage

At around 11:20 AM UTC, Cloudflare’s network began returning widespread HTTP 5xx errors, causing countless websites to become unreachable. In effect, a large part of the internet went dark.

Users encountered:

• “Internal Server Error”
• “Cloudflare’s network is down”
• Incomplete website loads
• Failed login challenges via Cloudflare Turnstile

The outage wasn’t limited to small websites. Even giants like X (formerly Twitter), ChatGPT, Shopify, Coinbase, Dropbox, NJ Transit, MTA, and many others went offline or partially degraded.

Even outage-tracking services like Downdetector faced issues because they themselves run on Cloudflare.

Cloudflare later confirmed no cyberattack was involved. The culprit was an internal system failure.

Technical Cause of the Outage

Cloudflare revealed that the outage was triggered by a software bug related to its Bot Management system. The issue began when:

1. A change in permissions on a Cloudflare database caused it to produce duplicate entries in an automatically generated configuration file.
2. This “feature file,” used for bot detection and traffic filtering, suddenly doubled in size.
3. Cloudflare’s global proxy software had a built-in file size limit.
4. When the oversized file was propagated across the network, Cloudflare’s core traffic-routing processes crashed instantly.

The failure became confusing because the faulty file regenerated every 5 minutes:

• If it was generated from an unmodified database node → normal (network came back)
• If from an updated node → bloated file (network crashed again)

This led to cycles of outages and brief recoveries, initially resembling a hyper-scale DDoS attack. Only after all database nodes began generating the bad file consistently did the error become clear.

Impact: What Went Down Globally

The outage was global, affecting both Cloudflare customers and Cloudflare’s own internal tools.

Major Websites & Platforms Impacted

• X (Twitter)
• OpenAI / ChatGPT
• Shopify
• Coinbase
• Dropbox
• League of Legends
• Letterboxd
• Various news outlets
• Government and public transit portals (NY MTA, NJ Transit)

Cloudflare Services Affected

1. CDN and Proxy Traffic
   • Returned HTTP 500 errors globally
   • Many websites failed to serve content entirely
2. Cloudflare Turnstile
   • CAPTCHA alternative failed to load
   • Logins and verifications blocked
3. Workers KV
   • Elevated error rates due to proxy outages
4. Zero Trust Access
   • New logins failed
   • Already logged-in users remained unaffected
5. Email Security
   • Temporary reduction in spam-filter accuracy

This episode sharply highlighted how deeply Cloudflare is embedded in the global internet—so much so that when it fails, the world feels it.

Timeline of Cloudflare’s Response

All times below are in UTC.

11:20 AM — Outage Begins

Cloudflare’s core proxy software crashes while loading the oversized config file. Websites worldwide begin showing error pages.

~12:00 PM — Issue Acknowledged

Cloudflare posts an alert saying it is investigating a multi-service impact. Engineers initially suspect a large-scale DDoS due to unusual traffic patterns.

12:45–14:00 PM — Investigation Intensifies

Error cycles continue. Logs eventually point toward the malformed Bot Management feature file. Engineers prepare to isolate and remove it.

14:30 PM — Fix Deployed

Cloudflare:

• Stops the generation of the faulty file
• Pushes a known-good configuration
• Restarts core proxy processes across its global network

Traffic begins to flow normally again.

14:45–14:50 PM — Incident Resolved

Cloudflare announces the fix has worked. CTO Dane Knecht publicly apologizes, confirming “This was not an attack.”

15:00–17:06 PM — Stabilization

Cloudflare engineers continue monitoring residual issues and restart any services stuck in a “bad state.”
At 17:06 UTC, Cloudflare confirms full restoration.

Economic Losses and Global Business Impact

Beyond technical disruption, the Cloudflare outage caused measurable economic damage across industries. With millions of sites unreachable, businesses experienced revenue loss, operational delays, and customer dissatisfaction.

1. E-Commerce Losses

Online retailers saw:

• Failed checkout pages
• Dropped carts
• Interrupted payment processes
• Traffic crashes during peak shopping hours

Large e-commerce enterprises reportedly lost millions in revenue during the downtime window.

2. Payment & Financial Service Disruptions

Because Cloudflare sits in front of many banking and fintech systems:

• Payment gateways stopped responding
• Bank and wallet login pages timed out
• Open-banking APIs failed
• Support centres were flooded
• Some institutions flagged compliance exceptions due to processing delays

3. SaaS Platforms and Communication Tools

ChatGPT, social networks, workplace apps, and productivity tools experienced:

• Reduced uptime
• Delayed customer workflows
• Sharp drops in user activity
• Temporary hit to trust and reliability perception

4. On-Demand, Real-Time, and Mobility Services

Apps that depend on real-time matching—like food delivery and ride-hailing—saw:

• Driver matching failures
• Cancelled orders
• Interrupted routing and tracking
• Loss of thousands of time-sensitive transactions

5. Global Reach of Financial Damage

The outage affected multiple regions simultaneously:

• North America
• Europe
• Asia-Pacific
• Middle East

This amplified losses in industries that operate globally.

6. Industry-Wide Estimates

• Studies show 92% of enterprise e-commerce merchants have faced similar disruptions in the past.
• Some global retailers have reported losses exceeding £10 million during major CDN outages.
• The event highlighted how dependent the digital economy is on centralized infrastructure.

Key Insight

The Cloudflare outage demonstrated that:

• Even a few hours of disruption in a core internet provider can cause massive global financial losses, operational slowdowns, and erosion of customer trust.
• Companies now face rising pressure to adopt multi-CDN, multi-DNS, and redundancy strategies to avoid single points of failure.

This incident made it clear that the modern digital economy is only as strong as the infrastructure layer supporting it.

Lessons and Future Directions

The November 2025 outage underscored the necessity for:

• Redundancy: Businesses must design multi-provider architectures to reduce single points of failure.
• Disaster Recovery: Reliable recovery protocols and continuous infrastructure monitoring are essential.
• Transparency: Timely, clear communications during outages build customer trust.

Cloudflare has pledged to improve backend safeguards, automate fault detection, and strengthen configuration controls to prevent recurrence.

The November 18 outage was one of Cloudflare’s most disruptive incidents in years. While no malicious activity was involved, the failure revealed how a single configuration error inside a global network can ripple across the entire internet.

Cloudflare has since stated it will:

• Audit configuration systems
• Strengthen file-size checks
• Improve fail-safes to prevent similar propagation bugs
• Enhance alerting systems for abnormal config growth

The incident highlights a simple truth:
When Cloudflare goes down, the internet feels it.

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