Window: sessionStorage property
The read-only sessionStorage
property accesses a session Storage
object for the current
origin. sessionStorage
is similar to
localStorage
; the difference is that while data
in localStorage
doesn't expire, data in sessionStorage
is
cleared when the page session ends.
- Whenever a document is loaded in a particular tab in the browser, a unique page session gets created and assigned to that particular tab. That page session is valid only for that particular tab.
- A page session lasts as long as the tab or the browser is open, and survives over page reloads and restores.
- Opening a page in a new tab or window creates a new session with the value of the top-level browsing context, which differs from how session cookies work.
-
Opening multiple tabs/windows with the same URL creates
sessionStorage
for each tab/window. -
Duplicating a tab copies the tab's
sessionStorage
into the new tab. -
Closing a tab/window ends the session and clears objects in
sessionStorage
.
Data stored in sessionStorage
is specific to the protocol of the
page. In particular, data stored by a script on a site accessed with HTTP
(e.g., http://example.com) is
put in a different sessionStorage
object from the same site accessed with
HTTPS (e.g., https://example.com).
The keys and the values are always in the UTF-16 string format, which uses two bytes per character. As with objects, integer keys are automatically converted to strings.
Value
A Storage
object which can be used to access the current origin's
session storage space.
Exceptions
SecurityError
-
Thrown in one of the following cases:
- The origin is not a valid scheme/host/port tuple. This can happen if the origin uses the
file:
ordata:
schemes, for example. - The request violates a policy decision. For example, the user has configured the browsers to prevent the page from persisting data.
Note that if the user blocks cookies, browsers will probably interpret this as an instruction to prevent the page from persisting data.
- The origin is not a valid scheme/host/port tuple. This can happen if the origin uses the
Examples
Basic usage
// Save data to sessionStorage
sessionStorage.setItem("key", "value");
// Get saved data from sessionStorage
let data = sessionStorage.getItem("key");
// Remove saved data from sessionStorage
sessionStorage.removeItem("key");
// Remove all saved data from sessionStorage
sessionStorage.clear();
Saving text between refreshes
The following example autosaves the contents of a text field, and if the browser is refreshed, restores the text field content so that no writing is lost.
// Get the text field that we're going to track
let field = document.getElementById("field");
// See if we have an autosave value
// (this will only happen if the page is accidentally refreshed)
if (sessionStorage.getItem("autosave")) {
// Restore the contents of the text field
field.value = sessionStorage.getItem("autosave");
}
// Listen for changes in the text field
field.addEventListener("change", () => {
// And save the results into the session storage object
sessionStorage.setItem("autosave", field.value);
});
Note: Please refer to the Using the Web Storage API article for a full example.
Specifications
Specification |
---|
HTML Standard # dom-sessionstorage-dev |
Browser compatibility
BCD tables only load in the browser