# Session Storage

URL: https://softwaredictionary.org/terms/session-storage
Category: Web Development
Last updated: 2026-10-06

In short: Session storage is a browser feature that saves text as key-value pairs for one tab only; the data survives reloads but is deleted when the tab is closed.

## What is session storage?

Session storage, used in JavaScript through the `sessionStorage` object, is part of the Web Storage API, alongside local storage. It stores strings under string keys with the same small set of methods: `setItem`, `getItem`, `removeItem` and `clear`. Objects are saved with `JSON.stringify` and read back with `JSON.parse`, and browsers typically allow about 5 MB per origin.

What sets it apart is its lifetime. The data belongs to one origin in one browser tab: it survives reloads and moving back and forth, but every new tab starts with its own empty storage, even for the same site, and closing the tab deletes it. A page opened from the tab with `window.open` starts with a copy, but after that the two are separate. This makes it a good fit for state that matters only during the current visit, such as a half-filled multi-step form, a scroll position or a message shown once per tab.

Think of session storage as a sticky note on one browser tab: handy while you work there and thrown away when you close it. Like local storage, it can be read by any script on the page, so a cross-site scripting (XSS) attack can steal what it holds, and it is no place for passwords or tokens.

The word session causes confusion. Session storage has nothing to do with a login session on the server or with session cookies: a session cookie is shared by every tab of the site, is sent to the server with each request and lasts until the browser closes, while `sessionStorage` stays in the browser, belongs to one tab and is never sent anywhere. Compared with local storage, the API is identical; only the lifetime and scope differ.

## Key takeaways

- Session storage saves string key-value pairs in the browser for a single tab.
- The data survives reloads but is deleted when the tab is closed.
- It has the same API as `localStorage`: `setItem`, `getItem`, `removeItem` and `clear`.
- Each new tab gets its own storage, even for the same site.
- It is unrelated to server sessions and is never sent with requests.

## Example: Keeping a form draft for the current tab only

```javascript
const form = document.querySelector("#signup");

// Save the fields on every change, for this tab only
form.addEventListener("input", () => {
  const data = Object.fromEntries(new FormData(form));
  sessionStorage.setItem("signup-draft", JSON.stringify(data));
});

// After a reload the draft comes back; a new tab starts empty
const draft = JSON.parse(sessionStorage.getItem("signup-draft") ?? "{}");
for (const [name, value] of Object.entries(draft)) {
  if (form.elements[name]) form.elements[name].value = value;
}
```

## Frequently asked questions

**What is the difference between sessionStorage and localStorage?**

They share the same API. `localStorage` data is shared by all tabs of a site and stays until it is deleted; `sessionStorage` data belongs to one tab and is deleted when that tab is closed.

**Does sessionStorage survive a page refresh?**

Yes. Reloading the page, or leaving and coming back in the same tab, keeps the data. Closing the tab, or the browser, clears it.

**Is sessionStorage shared between tabs?**

No. Each tab has its own storage, even for the same site. To share data between tabs, use `localStorage`, IndexedDB or a `BroadcastChannel`.

## Sources

- [HTML Living Standard: Web storage](https://html.spec.whatwg.org/multipage/webstorage.html)
- [MDN: Window: sessionStorage property](https://developer.mozilla.org/en-US/docs/Web/API/Window/sessionStorage)

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