How One Config File Took Down Cloudflare (The 2025 Outage Explained)

On November 18, 2025, websites around the world showed the same error page: your browser was working, the website's server was working, and the problem was in the middle, inside Cloudflare's network. It wasn't an attack. It came down to a file. We follow that file step by step, using Cloudflare's own post-mortems: what Cloudflare does: a reverse proxy in front of millions of websites Bot Management and the "feature file" rebuilt every five minutes a correct database permissions change, and a query that never named its database a limit of 200, a file with more than 200 features, and a Rust .unwrap() that crashed why the network kept flipping between working and broken, and why it looked like an attack code ships slowly, behind gates. Config shipped instantly, everywhere December 5, 2025: a kill switch, an old Lua bug, and 28% of HTTP traffic Code Orange: Fail Small: config rollouts in steps, fail stale, fail open, break glass the same lesson from CrowdStrike 2024, and Google SRE Code, queries and error messages on screen are quoted from Cloudflare's published post-mortems. Diagrams are sketches. Chapters 0:00 The same error page everywhere 0:54 What Cloudflare actually does 1:49 Bot Management and the feature file 2:36 11:05: a permissions change 3:31 A limit of 200 and an unwrap 4:24 Working, broken, working: was it an attack? 5:23 Code ships slowly. Config shipped instantly 6:29 December 5: it happened again 7:40 Code Orange: Fail Small 8:48 Not just Cloudflare 9:39 How one file took down a big piece of the web References Cloudflare outage on November 18, 2025: https://blog.cloudflare.com/18-novemb... Cloudflare outage on December 5, 2025: https://blog.cloudflare.com/5-decembe... Code Orange: Fail Small (Dec 19, 2025): https://blog.cloudflare.com/fail-smal... Code Orange: Fail Small is complete (May 1, 2026): https://blog.cloudflare.com/code-oran... Cloudflare bot score: https://developers.cloudflare.com/bot... How Cloudflare works: https://developers.cloudflare.com/fun... Cloudflare network and scale: https://www.cloudflare.com/about-over... W3Techs, Cloudflare usage statistics: https://w3techs.com/technologies/deta... CrowdStrike preliminary post-incident review: https://www.crowdstrike.com/en-us/blo... CrowdStrike Channel File 291 root cause analysis: https://www.crowdstrike.com/wp-conten... Microsoft, Helping our customers through the CrowdStrike outage: https://blogs.microsoft.com/blog/2024... Google SRE book, Introduction: https://sre.google/sre-book/introduct... Google SRE workbook, Postmortem analysis: https://sre.google/workbook/postmorte... Narration: synthetic voice (Kokoro). Music: "Vastness" by Andrew Ev (Mixkit), intro and outro only. #cloudflare #outage #softwareengineering