In Week 9 of the IBM Full-Stack JavaScript Developer track, I stepped back from tutorials and asked a different question: what is the internet actually running on?The answer isn’t the framework that trended on X this morning. It’s older, quieter, and far more stubborn.COBOL: the 67-year-old that moves your money. Created in 1959, COBOL is still widely estimated to sit behind about 95% of ATM transactions and 80% of in-person banking transactions, with some 220 billion lines in production and around $3 trillion in commerce a day. One example: back in 2012, Bank of New York Mellon reported maintaining 112,500 COBOL programs, about 343 million lines of code. The catch is a talent gap. Universities largely stopped teaching it decades ago, and banks are now experimenting with AI tools to help maintain and modernize it.PHP and WordPress: the web’s workhorse. PHP is used by about 70% of websites whose server-side language is known. WordPress, built on it, runs roughly 42% of all websites.jQuery: declared dead, still everywhere. It’s on about 67% of all websites. Even jQuery 1.x, a version from the 2000s, is still found on around 13%.Linux: the invisible foundation. About 62% of websites with an identifiable OS run Linux, and the broader Unix family covers around 92%. Every system on the TOP500 supercomputer list runs Linux too.And the new stuff earns its place. React Native isn’t legacy, but it shows why tools survive: Shopify moved its flagship app to it and now shares about 86% of its code across iOS and Android, up from roughly 5%. Efficiency like that is why a tool lasts.My takeaway: the technologies that last aren’t the newest; they’re the ones that are reliable, and rewriting something that works is expensive and risky. As a developer, learning the new tools matters, but so does respecting the old systems that keep running.What’s the oldest piece of tech you’ve seen still running in production?Sources: W3Techs (2026), Reuters (2017), Computerworld (2012), Shopify’s React Native migration. Usage figures cover only sites where the technology is detectable.