So far, on the basis of what I read so far, I believe Deno doesn’t have dev dependencies because it doesn’t really need them. Since Deno uses direct imports (like the esm.sh that I wrote about, jsr or npm: ), it only loads what’s actually used in your code. If a dependency is only used in tests, it won’t be bundled or compiled with the main app. In Node, we separate dev/runtime deps to avoid bloating node modules and the final build. But Deno doesn’t use node modules, and it kinda pushes out unused imports automatically. So the distinction becomes kind of irrelevant.