🧠 Why Do You See Client Component HTML in View Page Source in Next.js?

Many developers assume that if a component uses 'use client' in Next.js, it will render entirely on the client-side, and nothing will show up in the View Page Source.
But surprisingly, sometimes you can see HTML output from a Client Component in the page source!
Is that a bug?
Not at all. It’s actually part of Next.js’s smart optimization strategies.


✅ So, Why Does This Happen?

Here are a few common reasons why client components still show HTML in the source:
🔹 Static Content Injection:
If your client component contains static or predictable JSX (like <h1>Hello World</h1>), Next.js can pre-render that HTML during the build, even though it's a client component.
🔹 Hydration Skeletons:
Next.js may render initial HTML as a skeleton for hydration purposes. This improves performance and perceived loading speed.
🔹 Partial Rendering (App Router):
With the App Router in Next.js 13/14, components can be partially rendered — some parts are server-rendered, and others are client-rendered, seamlessly integrated.
🔹 No Dynamic Data:
If your client component doesn’t fetch any dynamic data and only returns static content, Next.js can safely pre-render it.