When you first visit a modern site, the server sends a fast-loading snapshot of the page that looks complete but cannot be clicked yet.

Websites as Static Pictures

Hydration is the process where a browser takes that static snapshot and attaches the programming needed to make it interactive.

Waking Up with Hydration

Traditional hydration is often slow because the browser has to re-run all the work the server already did just to figure out what the page does.

Starting from Scratch Again

Resumability is a newer technique where a website 'pauses' on the server and 'resumes' in your browser exactly where it left off without re-doing any work.

The Magic of Resumability

Unlike hydration, which restarts the engine, resumability acts like a video game save file that lets you start playing immediately from the last checkpoint.

Continuing from a Pause

Instead of downloading all the code at once, resumable sites only fetch the specific instructions for a button at the exact moment you actually click it.

Loading Code on Demand

Some frameworks only wake up the small interactive parts of a page, like a search bar, while keeping the rest of the page simple and fast.

Small Islands of Activity

Because resumability skips the 're-starting' phase, websites feel much faster and more responsive, especially on slower phones or internet connections.

Instant Speed for Users

Different web tools use these methods differently; for example, React uses hydration, while a tool called Qwik focuses on resumability.

The Mystery of Slow Sites