Window.sessionStorage
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 DOMString
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
-
The request violates a policy decision, or the origin is not a valid scheme/host/port tuple (this can happen if the origin uses the
file:
ordata:
scheme, for example). For example, the user may have their browser configured to deny permission to persist data for the specified origin.
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", function() {
// 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