The Web Can't Afford a JavaScript Runtime Monoculture

Deno’s planned shutdown a year after its team joined Cloudflare leaves JavaScript with fewer independent server runtimes: Node.js and Bun remain major general-purpose alternatives, while Cloudflare’s workerd mainly serves its Workers platform. The concern is not simply that Deno is disappearing, but that server-side JavaScript is following browsers toward a small set of dominant implementations. Most major runtimes use Google’s V8 engine, with Bun relying on Apple’s JavaScriptCore. The history of Internet Explorer 6 and browser-engine consolidation shows how a market with too little competition can slow progress and leave developers dependent on one implementation’s choices.

Runtime diversity matters for both standards and resilience. Shared server APIs risk reflecting the behavior of the most widely used runtime if too few independent implementations help shape them. Common engines can also spread the effects of a serious flaw across many systems, as the widespread OpenSSL vulnerability Heartbleed illustrated. Competition has already produced practical gains: Deno helped popularize permission-based security and features such as TypeScript support, while Bun has emphasized speed; pressure from alternatives also encouraged Node to adopt capabilities developers wanted. OpenJS governance can protect Node’s community oversight, but cannot replace competition. New Deno-inspired projects such as Ende and Dodo show that alternatives may emerge, though their early state underscores how difficult sustained independent development is. The broader case is that a diverse ecosystem makes the web more robust and keeps runtimes improving.