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Let’s DO this: detecting Workers Builds errors across 1 million Durable Objects

Cloudflare Workers Builds is our CI/CD product that makes it easy to build and deploy Workers applications every time code is pushed to GitHub or GitLab. What makes Workers Builds special is that projects can be built and deployed with minimal configuration. Just hook up your project and let us take care of the rest!

But what happens when things go wrong, such as failing to install tools or dependencies? What usually happens is that we don’t fix the problem until a customer contacts us about it, at which point many other customers have likely faced the same issue. This can be a frustrating experience for both us and our customers because of the lag time between issues occurring and us fixing them.

We want Workers Builds to be reliable, fast, and easy to use so that developers can focus on building, not dealing with our bugs. That’s why we recently started building an error detection system that can detect, categorize, and surface all build issues occurring on Workers Builds, enabling us to proactively fix issues and add missing features.

It’s also no secret that we’re big fans of being “Customer Zero” at Cloudflare, and Workers Builds is itself a Continue reading

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Cloudflare named in 2025 Gartner® Magic Quadrant™ for Security Service Edge

For the third consecutive year, Gartner has named Cloudflare in the Gartner® Magic Quadrant™ for Security Service Edge (SSE) report. This analyst evaluation helps security and network leaders make informed choices about their long-term partners in digital transformation. We are excited to share that Cloudflare is one of only nine vendors recognized in this year’s report. You can read more about our position in the report here.

What’s more exciting is that we’re just getting started. Since 2018, starting with our Zero Trust Network Access (ZTNA) service Cloudflare Access, we’ve continued to push the boundaries of how quickly we can build and deliver a mature SSE platform. In that time, we’ve released multiple products each year, delivering hundreds of features across our platform. That’s not possible without our customers. Today, tens of thousands of customers have chosen to connect and protect their people, devices, applications, networks, and data with Cloudflare. They tell us our platform is faster and easier to deploy and provides a more consistent and reliable user experience, all on a more agile architecture for longer term modernization. We’ve made a commitment to those customers to continue to deliver innovative solutions with the velocity and resilience Continue reading

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Resolving a request smuggling vulnerability in Pingora

On April 11, 2025 09:20 UTC, Cloudflare was notified via its Bug Bounty Program of a request smuggling vulnerability in the Pingora OSS framework discovered by a security researcher experimenting to find exploits using Cloudflare’s Content Delivery Network (CDN) free tier which serves some cached assets via Pingora.

Customers using the free tier of Cloudflare’s CDN or users of the caching functionality provided in the open source pingora-proxy and pingora-cache crates could have been exposed.  Cloudflare’s investigation revealed no evidence that the vulnerability was being exploited, and was able to mitigate the vulnerability by April 12, 2025 06:44 UTC within 22 hours after being notified.

The bug bounty report detailed that an attacker could potentially exploit an HTTP/1.1 request smuggling vulnerability on Cloudflare’s CDN service. The reporter noted that via this exploit, they were able to cause visitors to Cloudflare sites to make subsequent requests to their own server and observe which URLs the visitor was originally attempting to access.

We treat any potential request smuggling or caching issue with extreme urgency.  After our security team escalated the vulnerability, we began investigating immediately, took steps to disable traffic to vulnerable components, and deployed Continue reading

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Bringing connections into view: real-time BGP route visibility on Cloudflare Radar

The Internet relies on the Border Gateway Protocol (BGP) to exchange IP address reachability information. This information outlines the path a sender or router can use to reach a specific destination. These paths, conveyed in BGP messages, are sequences of Autonomous System Numbers (ASNs), with each ASN representing an organization that operates its own segment of Internet infrastructure.

Throughout this blog post, we'll use the terms "BGP routes" or simply "routes" to refer to these paths. In essence, BGP functions by enabling autonomous systems to exchange routes to IP address blocks (“IP prefixes”), allowing different entities across the Internet to construct their routing tables.

When network operators debug reachability issues or assess a resource's global reach, BGP routes are often the first thing they examine. Therefore, it’s critical to have an up-to-date view of the routes toward the IP prefixes of interest. Some networks provide tools called "looking glasses" — public routing information services offering data directly from their own BGP routers. These allow external operators to examine routes from that specific network's perspective. Furthermore, services like bgp.tools, bgp.he.net, RouteViews, or the NLNOG RING looking glass offer aggregated, looking glass-like lookup capabilities, drawing Continue reading

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Performance measurements… and the people who love them

⚠️ WARNING ⚠️ This blog post contains graphic depictions of probability. Reader discretion is advised.

Measuring performance is tricky. You have to think about accuracy and precision. Are your sampling rates high enough? Could they be too high?? How much metadata does each recording need??? Even after all that, all you have is raw data. Eventually for all this raw performance information to be useful, it has to be aggregated and communicated. Whether it's in the form of a dashboard, customer report, or a paged alert, performance measurements are only useful if someone can see and understand them.

This post is a collection of things I've learned working on customer performance escalations within Cloudflare and analyzing existing tools (both internal and commercial) that we use when evaluating our own performance.  A lot of this information also comes from Gil Tene's talk, How NOT to Measure Latency. You should definitely watch that too (but maybe after reading this, so you don't spoil the ending). I was surprised by my own blind spots and which assumptions turned out to be wrong, even though they seemed "obviously true" at the start. I expect I am not alone in these regards. For that Continue reading

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Your IPs, your rules: enabling more efficient address space usage

IPv4 addresses have become a costly commodity, driven by their growing scarcity. With the original pool of 4.3 billion addresses long exhausted, organizations must now rely on the secondary market to acquire them. Over the years, prices have surged, often exceeding $30–$50 USD per address, with costs varying based on block size and demand. Given the scarcity, these prices are only going to rise, particularly for businesses that haven’t transitioned to IPv6. This rising cost and limited availability have made efficient IP address management more critical than ever. In response, we’ve evolved how we handle BYOIP (Bring Your Own IP) prefixes to give customers greater flexibility.

Historically, when customers onboarded a BYOIP prefix, they were required to assign it to a single service, binding all IP addresses within that prefix to one service before it was advertised. Once set, the prefix's destination was fixed — to direct traffic exclusively to that service. If a customer wanted to use a different service, they had to onboard a new prefix or go through the cumbersome process of offboarding and re-onboarding the existing one.

As a step towards addressing this limitation, we’ve introduced a new level of flexibility: customers can Continue reading

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Vulnerability transparency: strengthening security through responsible disclosure

In an era where digital threats evolve faster than ever, cybersecurity isn't just a back-office concern — it's a critical business priority. At Cloudflare, we understand the responsibility that comes with operating in a connected world. As part of our ongoing commitment to security and transparency, Cloudflare is proud to have joined the United States Cybersecurity and Infrastructure Security Agency’s (CISA) “Secure by Design” pledge in May 2024. 

By signing this pledge, Cloudflare joins a growing coalition of companies committed to strengthening the resilience of the digital ecosystem. This isn’t just symbolic — it's a concrete step in aligning with cybersecurity best practices and our commitment to protect our customers, partners, and data. 

A central goal in CISA’s Secure by Design pledge is promoting transparency in vulnerability reporting. This initiative underscores the importance of proactive security practices and emphasizes transparency in vulnerability management — values that are deeply embedded in Cloudflare’s Product Security program. ​We believe that openness around vulnerabilities is foundational to earning and maintaining the trust of our customers, partners, and the broader security community.

Transparency in vulnerability reporting is essential for building trust between companies and customers. In 2008, Continue reading

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Forget IPs: using cryptography to verify bot and agent traffic

With the rise of traffic from AI agents, what’s considered a bot is no longer clear-cut. There are some clearly malicious bots, like ones that DoS your site or do credential stuffing, and ones that most site owners do want to interact with their site, like the bot that indexes your site for a search engine, or ones that fetch RSS feeds.      

Historically, Cloudflare has relied on two main signals to verify legitimate web crawlers from other types of automated traffic: user agent headers and IP addresses. The User-Agent header allows bot developers to identify themselves, i.e. MyBotCrawler/1.1. However, user agent headers alone are easily spoofed and are therefore insufficient for reliable identification. To address this, user agent checks are often supplemented with IP address validation, the inspection of published IP address ranges to confirm a crawler's authenticity. However, the logic around IP address ranges representing a product or group of users is brittle – connections from the crawling service might be shared by multiple users, such as in the case of privacy proxies and VPNs, and these ranges, often maintained by cloud providers, change over time.

Cloudflare will always try to block malicious bots, but Continue reading

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First-party tags in seconds: Cloudflare integrates Google tag gateway for advertisers

If you’re a marketer, advertiser, or a business owner that runs your own website, there’s a good chance you’ve used Google tags in order to collect analytics or measure conversions. A Google tag is a single piece of code you can use across your entire website to send events to multiple destinations like Google Analytics and Google Ads. 

Historically, the common way to deploy a Google tag meant serving the JavaScript payload directly from Google’s domain. This can work quite well, but can sometimes impact performance and accurate data measurement. That’s why Google developed a way to deploy a Google tag using your own first-party infrastructure using server-side tagging. However, this server-side tagging required deploying and maintaining a separate server, which comes with a cost and requires maintenance.

That’s why we’re excited to be Google’s launch partner and announce our direct integration of Google tag gateway for advertisers, providing many of the same performance and accuracy benefits of server-side tagging without the overhead of maintaining a separate server.  

Any domain proxied through Cloudflare can now serve your Google tags directly from that domain. This allows you to get better measurement signals for your website and can enhance your Continue reading

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QUIC restarts, slow problems: udpgrm to the rescue

At Cloudflare, we do everything we can to avoid interruption to our services. We frequently deploy new versions of the code that delivers the services, so we need to be able to restart the server processes to upgrade them without missing a beat. In particular, performing graceful restarts (also known as "zero downtime") for UDP servers has proven to be surprisingly difficult.

We've previously written about graceful restarts in the context of TCP, which is much easier to handle. We didn't have a strong reason to deal with UDP until recently — when protocols like HTTP3/QUIC became critical. This blog post introduces udpgrm, a lightweight daemon that helps us to upgrade UDP servers without dropping a single packet.

Here's the udpgrm GitHub repo.

In the early days of the Internet, UDP was used for stateless request/response communication with protocols like DNS or NTP. Restarts of a server process are not a problem in that context, because it does not have to retain state across multiple requests. However, modern protocols like QUIC, WireGuard, and SIP, as well as online games, use stateful flows. So what happens to the state associated with a flow when a server process is Continue reading

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Scaling with safety: Cloudflare’s approach to global service health metrics and software releases

Has your browsing experience ever been disrupted by this error page? Sometimes Cloudflare returns "Error 500" when our servers cannot respond to your web request. This inability to respond could have several potential causes, including problems caused by a bug in one of the services that make up Cloudflare's software stack.

We know that our testing platform will inevitably miss some software bugs, so we built guardrails to gradually and safely release new code before a feature reaches all users. Health Mediated Deployments (HMD) is Cloudflare’s data-driven solution to automating software updates across our global network. HMD works by querying Thanos, a system for storing and scaling Prometheus metrics. Prometheus collects detailed data about the performance of our services, and Thanos makes that data accessible across our distributed network. HMD uses these metrics to determine whether new code should continue to roll out, pause for further evaluation, or be automatically reverted to prevent widespread issues.

Cloudflare engineers configure signals from their service, such as alerting rules or Service Level Objectives (SLOs). For example, the following Service Level Indicator (SLI) checks the rate of HTTP 500 errors over 10 minutes returned from a service in our software stack.

sum(rate(http_request_count{code="500"}[10m]))  Continue reading

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Thirteen new MCP servers from Cloudflare you can use today

You can now connect to Cloudflare's first publicly available remote Model Context Protocol (MCP) servers from Claude.ai (now supporting remote MCP connections!) and other MCP clients like Cursor, Windsurf, or our own AI Playground. Unlock Cloudflare tools, resources, and real time information through our new suite of MCP servers including: 

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MCP Demo Day: How 10 leading AI companies built MCP servers on Cloudflare

Today, we're excited to collaborate with Anthropic, Asana, Atlassian, Block, Intercom, Linear, PayPal, Sentry, Stripe, and Webflow to bring a whole new set of remote MCP servers, all built on Cloudflare, to enable Claude users to manage projects, generate invoices, query databases, and even deploy full stack applications — without ever leaving the chat interface. 

Since Anthropic’s introduction of the Model Context Protocol (MCP) in November, there’s been more and more excitement about it, and it seems like a new MCP server is being released nearly every day. And for good reason!  MCP has been the missing piece to make AI agents a reality, and helped define how AI agents interact with tools to take actions and get additional context.

But to date, end-users have had to install MCP servers on their local machine to use them. Today, with Anthropic’s announcement of Integrations, you can access an MCP server the same way you would a website: type a URL and go.

At Cloudflare, we’ve been focused on building out the tooling that simplifies the development of remote MCP servers, so that our customers’ engineering teams can focus their time on building out the MCP tools for their Continue reading

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Bringing streamable HTTP transport and Python language support to MCP servers

We’re continuing to make it easier for developers to bring their services into the AI ecosystem with the Model Context Protocol (MCP). Today, we’re announcing two new capabilities:

• Streamable HTTP Transport: The Agents SDK now supports the new Streamable HTTP transport, allowing you to future-proof your MCP server. Our implementation allows your MCP server to simultaneously handle both the new Streamable HTTP transport and the existing SSE transport, maintaining backward compatibility with all remote MCP clients.

• Deploy MCP servers written in Python: In 2024, we introduced first-class Python language support in Cloudflare Workers, and now you can build MCP servers on Cloudflare that are entirely written in Python.

Click “Deploy to Cloudflare” to get started with a remote MCP server that supports the new Streamable HTTP transport method, with backwards compatibility with the SSE transport. 

The MCP spec was updated on March 26 to introduce a new transport mechanism for remote MCP, called Streamable HTTP. The new transport simplifies how AI agents can interact with services by using a single HTTP endpoint for sending and receiving responses between the client and the Continue reading

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How the April 28, 2025, power outage in Portugal and Spain impacted Internet traffic and connectivity

A massive power outage struck significant portions of Portugal and Spain at 10:34 UTC on April 28, grinding transportation to a halt, shutting retail businesses, and otherwise disrupting everyday activities and services. Parts of France were also reportedly impacted by the power outage. Portugal’s electrical grid operator blamed the outage on a "fault in the Spanish electricity grid”, and later stated that "due to extreme temperature variations in the interior of Spain, there were anomalous oscillations in the very high voltage lines (400 kilovolts), a phenomenon known as 'induced atmospheric vibration'" and that "These oscillations caused synchronisation failures between the electrical systems, leading to successive disturbances across the interconnected European network." However, the operator later denied these claims. 

The breadth of Cloudflare’s network and our customer base provides us with a unique perspective on Internet resilience, enabling us to observe the Internet impact of this power outage at both a local and national level, as well as at a network level, across traffic, network quality, and routing metrics.

In Portugal, Internet traffic dropped as the power grid failed, with traffic immediately dropping by half as compared to the Continue reading

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Targeted by 20.5 million DDoS attacks, up 358% year-over-year: Cloudflare’s 2025 Q1 DDoS Threat Report

Welcome to the 21st edition of the Cloudflare DDoS Threat Report. Published quarterly, this report offers a comprehensive analysis of the evolving threat landscape of Distributed Denial of Service (DDoS) attacks based on data from the Cloudflare network. In this edition, we focus on the first quarter of 2025. To view previous reports, visit www.ddosreport.com.

While this report primarily focuses on 2025 Q1, it also includes late-breaking data from a hyper-volumetric DDoS campaign observed in April 2025, featuring some of the largest attacks ever publicly disclosed. In a historic surge of activity, we blocked the most intense packet rate attack on record, peaking at 4.8 billion packets per second (Bpps), 52% higher than the previous benchmark, and separately defended against a massive 6.5 terabits-per-second (Tbps) flood, matching the highest bandwidth attacks ever reported.

• In the first quarter of 2025, Cloudflare blocked 20.5 million DDoS attacks. That represents a 358% year-over-year (YoY) increase and a 198% quarter-over-quarter (QoQ) increase. 

• Around one third of those, 6.6 million, targeted the Cloudflare network infrastructure directly, as part of an 18-day multi-vector attack campaign.

• Furthermore, in the first quarter of 2025, Cloudflare blocked approximately Continue reading

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New year, no shutdowns: the Q1 2025 Internet disruption summary

Cloudflare’s network spans more than 330 cities in over 125 countries, where we interconnect with over 13,000 network providers in order to provide a broad range of services to millions of customers. The breadth of both our network and our customer base provides us with a unique perspective on Internet resilience, enabling us to observe the impact of Internet disruptions at both a local and national level, as well as at a network level.

As we have noted in the past, this post is intended as a summary overview of observed and confirmed disruptions, and is not an exhaustive or complete list of issues that have occurred during the quarter. A larger list of detected traffic anomalies is available in the Cloudflare Radar Outage Center. Note that both bytes-based and request-based traffic graphs are used within the post to illustrate the impact of the observed disruptions — the choice of metric was generally made based on which better illustrated the impact of the disruption.

In the first quarter of 2025, we observed a significant number of Internet disruptions due to cable damage and power outages. Severe storms caused outages in Ireland and Réunion, and an earthquake caused ongoing connectivity issues Continue reading

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Why I joined Cloudflare: to build world-class partnerships in EMEA

Cloudflare is not just another technology company. It’s a mission-driven force, committed to helping build a better Internet; one that is faster, safer, and more resilient. That mission is more critical than ever as organizations worldwide navigate an increasingly complex digital landscape, rife with cyber threats, regulatory challenges, and the need for scalable, cost-effective solutions.

In EMEA, that mission has special significance. The region is a patchwork of diverse markets, industries, and regulatory environments. It demands a partner-centric approach, one that empowers businesses of all sizes to harness Cloudflare’s comprehensive connectivity cloud platform to protect, connect, and accelerate their operations. That’s why I joined Cloudflare as VP of EMEA Partnerships.

Every great company has an inflection point, a moment when the market, the strategy, and the execution align to create unstoppable momentum. Cloudflare is at that moment now.

With record revenue growth, increasing traction among large customers, and an expanding suite of Zero Trust, AI, and network security solutions, Cloudflare is emerging as the partner of choice for enterprises and service providers across EMEA .

But what excites me most is the people, the opportunity to build a team in EMEA that is world-class in its expertise, Continue reading

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Why I joined Cloudflare as Chief People Officer — Kelly Russell

After years navigating the exhilarating world of high-growth tech, from Amazon to Twilio’s scaling journey and most recently Wiz’s rapid ascent, I’ve learned to recognize a truly special opportunity when I see one. That’s exactly what I have found at Cloudflare and why I’m thrilled to join. 

What drew me to Cloudflare was the unique combination of a powerful mission, a transparent and results-oriented culture, and the sheer scale of impact. Cloudflare isn’t just a technology company —  it’s a force for good, building a better Internet for everyone. This really resonates with my own values.  

My career has been defined by building, scaling, and developing teams in dynamic environments.  I’ve witnessed the transformative power of a strong culture in driving hypergrowth. I’ve experienced the intensity and agility required to disrupt a market. These experiences have reinforced my belief that people are the heart of any successful company, and that a people-first strategy is critical for long-term impact. During my interview process at Cloudflare, this belief was clearly evident in every conversation. Cloudflare is a place where people can do their best work and be proud of the impact they are making. Powered Continue reading

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Developer Week 2025 wrap-up

As we conclude Developer Week 2025, we’re proud to reflect upon the capabilities we’ve added to our developer platform. It’s so rewarding to deliver products, features and tools that help developers build smarter and ship faster, and even more so hearing your responses throughout the week!

Our VP of Product, Rita Kozlov, kicked off Developer Week 2025 discussing the ever-evolving landscape of development, particularly in the age of AI. AI is no longer just a buzzword or a trope for a science-fiction future — in the realm of modern development, it’s a core tenet (and utility) of how we build, innovate, and solve problems. It’s influencing how and how frequently we ship code, as well as enabling anyone to write it.

It’s exciting to not only witness this technical revolution, but also to be building a platform that enables developers to be part of it. We want to hear your feedback and see what you build with the new capabilities — reach out to us on Discord or X.

Here’s a recap of our Developer Week 2025 announcements:

Announcement	Summary
Piecing together the Agent puzzle: MCP, authentication & authorization, and Durable Objects free tier	Toolkit for AI Continue reading