What Is Vapor Mode?
Vapor Mode is Vue's experimental compilation target that updates the DOM directly — skipping the virtual DOM runtime. Here's the one-line mental model and why it exists.
What it is#
Vapor Mode is an alternative compilation target for Vue's template compiler. Normally, a Vue template compiles to a render function that produces a virtual DOM tree, which the runtime then diffs and patches. In Vapor Mode, the compiler instead emits code that creates real DOM nodes once and mutates them directly when state changes — no virtual DOM tree, no diff pass, no per-update allocations.
Think of it as the same template, a different output: less JavaScript to ship and less work to do on every update.
Why you'd care#
Two wins, both about scale:
- Smaller runtime. Vapor components don't need the vdom renderer machinery per component, so the framework footprint drops.
- Cheaper updates. No vnode objects allocated and no tree walked on update — the work is proportional only to the dynamic parts of your template.
If you've never felt the vdom "tax" (lesson 2), this is foreshadowing. If you have — huge lists, many tiny components, high-frequency updates — this is the lever.
Before#
"Vue renders by building a virtual DOM tree and diffing it against the previous one." That's the mental model most of us carry, and it's still the default.
After#
"Vue can also compile a template straight to a sequence of direct DOM operations." Vapor Mode is opt-in and experimental — the vdom path is still the default and still fully supported. You turn Vapor on for a build; nothing about how you write components changes at the syntax level.
Do it yourself#
None yet — this is the conceptual setup. Lesson 4 gets your hands on the actual setup.
Gotchas#
- Vapor Mode is not a replacement for the virtual DOM yet. It's an opt-in mode you enable deliberately.
- It does not change Vue's reactivity (Proxies). It changes what happens after reactivity fires — where the DOM writes go.
- Because it's experimental, the enablement API and supported surface shift between versions. This series pins one version (see the setup lesson).
Recap#
Vapor Mode = compile templates to direct DOM ops instead of vdom diffing. Opt-in, experimental, reactivity unchanged. The next two lessons explain the "why" and the "how."