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Playwright does not restore sessionStorage through its normal storageState file. Read the JSON in your test process, then register a BrowserContext.addInitScript callback that writes the entries into window.sessionStorage before application scripts run. Scope the callback to the intended origin and convert every value to a string.
The documented approach
Playwright’s authentication guide documents an init-script workaround because its reusable storage state covers cookies, local storage, IndexedDB and WebAuthn passkeys, but not session storage. The sequence is:
- Save or receive a JSON object containing the session-storage entries.
- Parse that object in Node.js, outside the browser.
- Create a browser context.
- Call
context.addInitScript()before opening or navigating pages that need the data. - Write each entry with
sessionStorage.setItem()when the page belongs to the target origin.
See the official guidance in Playwright Authentication and the execution details in the BrowserContext API.
Complete TypeScript example
Assume playwright/.auth/session.json contains a JSON object such as {"cartId":"abc123","onboarding":"complete"}. The following script loads it and seeds pages on example.com:
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import fs from 'node:fs';
import { chromium } from 'playwright';
const sessionStorage = JSON.parse(
fs.readFileSync('playwright/.auth/session.json', 'utf-8'),
);
const browser = await chromium.launch();
const context = await browser.newContext();
await context.addInitScript((storage) => {
if (window.location.hostname !== 'example.com') return;
for (const [key, value] of Object.entries(storage)) {
window.sessionStorage.setItem(key, String(value));
}
}, sessionStorage);
const page = await context.newPage();
await page.goto('https://example.com/');
console.log(await page.evaluate(() => ({
cartId: sessionStorage.getItem('cartId'),
onboarding: sessionStorage.getItem('onboarding'),
})));
await browser.close();Replace the hostname and file path with your application’s values. The callback runs after a document is created but before that document’s own scripts execute, so a single-page application can read the seeded values during startup. Register it before newPage() and before any navigation that depends on the data.
Origin, scheme, port and frame scope
Web Storage is origin-scoped. The origin includes the scheme, hostname and port: https://app.example.com, http://app.example.com and https://app.example.com:8443 are different origins. A hostname-only check is suitable for the simple official example, but use a stricter guard when your test visits multiple environments:
await context.addInitScript((storage) => {
const allowed = new Set([
'https://app.example.com',
'https://app.example.com:8443',
]);
if (!allowed.has(window.location.origin)) return;
for (const [key, value] of Object.entries(storage)) {
window.sessionStorage.setItem(key, String(value));
}
}, sessionStorage);addInitScript applies to pages in the context, including later navigations. It can also execute in child frames. That is useful when the target application stores data in a same-origin iframe, but it means the guard is important: without one, unrelated pages or frames in the context could receive the same values.
JSON types and storage semantics
The Web Storage API stores strings. Calling String(value) makes numbers and booleans usable, but it turns an object into [object Object] and an array into a comma-separated string. Serialize structured values deliberately:
await context.addInitScript((storage) => {
if (window.location.origin !== 'https://example.com') return;
for (const [key, value] of Object.entries(storage)) {
const encoded = typeof value === 'string'
? value
: JSON.stringify(value);
window.sessionStorage.setItem(key, encoded);
}
}, sessionStorage);On the application side, parse values that were encoded as JSON:
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const preferences = JSON.parse(
sessionStorage.getItem('preferences') ?? '{}',
);If the file is meant to be a direct snapshot, save strings in it and avoid ambiguity. Validate the parsed result before passing it to the page:
if (!sessionStorage || typeof sessionStorage !== 'object' || Array.isArray(sessionStorage)) {
throw new Error('Session storage JSON must be an object');
}Creating a session-storage JSON file
The authentication guide shows how to extract the current page’s values by serializing the browser’s storage, then parse that file when creating a new context:
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fs.writeFileSync('playwright/.auth/session.json', json, 'utf8');Run the extraction on the same origin as the values you need. Session storage belongs to that origin and browser context; a file collected from one host does not automatically apply to another host.
Using Playwright Test fixtures
With Playwright Test, install the init script on the supplied context fixture before the test navigates. The runner’s storageState option can continue to provide cookies and other supported state independently.
import { test as base, expect } from '@playwright/test';
import fs from 'node:fs';
const sessionStorage = JSON.parse(
fs.readFileSync('playwright/.auth/session.json', 'utf8'),
);
export const test = base.extend({
context: async ({ context }, use) => {
await context.addInitScript((storage) => {
if (window.location.origin !== 'https://example.com') return;
for (const [key, value] of Object.entries(storage)) {
window.sessionStorage.setItem(key, String(value));
}
}, sessionStorage);
await use(context);
},
});
export { expect };Use the extended fixture in a test:
import { test, expect } from './fixtures';
test('opens the prepared account page', async ({ page }) => {
await page.goto('https://example.com/account');
await expect(page).toHaveURL(/account/);
});If you configure storageState in playwright.config.ts, remember that it does not replace this script for session storage. The supported test-runner option is described in the TestOptions API.
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Authentication and security
Session storage can contain bearer tokens, temporary credentials or identifiers that impersonate a user. Playwright warns that saved authentication state may contain sensitive cookies and headers; protect a session JSON file with the same care.
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- Keep it outside source control and add the directory to
.gitignore. - Use filesystem permissions and CI secret storage appropriate for the account.
- Prefer a test account with limited privileges.
- Delete generated files when a run or debugging session ends.
- Never print token values in test logs or failure diagnostics.
Do not assume session storage is the actual login mechanism. Inspect the application: authentication may instead use cookies, local storage, IndexedDB or a server-side session. Use Playwright’s normal storageState flow for the supported stores and add this workaround only for the session-storage portion.
Common failures and fixes
The application still behaves as logged out
Check that the script was registered before newPage() or navigation, and that the URL’s exact origin passes your guard. Also verify that the application reads session storage rather than a cookie or another store.
Values appear as the wrong type
Storage always returns strings. If the application expects an object, write it with JSON.stringify and read it with JSON.parse. Do not rely on JavaScript’s default conversion for arrays or objects.
The script seeds an unintended site
Replace a broad hostname check with an explicit set of origins. Include the correct HTTPS scheme, subdomain and non-default port, and retain the guard for child frames.
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A page opened before the callback was installed
Init scripts affect future document creation and navigations. Install the callback immediately after creating the context. For an already loaded page, set the values with page.evaluate and reload if the application only reads them during startup.
The JSON file cannot be parsed
Ensure it is UTF-8 JSON containing one object, not a JavaScript module, comments or a copied browser-export wrapper. Log only the keys while debugging, never secrets.
State leaks between tests
Use a fresh context per test or clear the relevant keys. A context shares its storage among pages of the same origin, so reusing one context can intentionally or accidentally carry values forward.
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The documented workaround remains relevant even as Playwright adds storage APIs. The current references list BrowserContext.setStorageState in v1.59, Web Storage APIs in v1.61, IndexedDB capture in v1.51, WebAuthn credential capture in v1.61 and OPFS capture in v1.63. Check the version installed in your project before using those adjacent features; none makes the init-script method unnecessary for a JSON session-storage seed.
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Performance and reliability considerations
- Parsing a small JSON object in the test process is inexpensive; avoid putting large application caches into every context.
- Seed only the keys required for the scenario, which reduces accidental coupling to expired data.
- Use deterministic fixture files for repeatable tests, and regenerate them when the application changes its storage schema.
- When tests run in parallel, give workers independent files or accounts if values represent mutable user state.
- Keep the init callback synchronous and simple. Network calls or asynchronous setup belong in the test fixture, not in the storage-writing loop.
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FAQ
Can I put session storage directly in storageState?
No. Use an init script to write the values before page scripts execute; storageState does not persist sessionStorage.
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The init script can run in child frames, but your origin guard must permit the frame’s actual origin.
Should I store tokens in a repository for CI?
No. Treat the JSON as authentication material, keep it out of source control and provide it through protected CI storage.
Frequently Asked Questions
Can I put session storage directly in storageState?
No. Use an init script to write the values before page scripts execute; storageState does not persist sessionStorage.
Does this work for every frame?
The init script can run in child frames, but your origin guard must permit the frame’s actual origin.
Should I store tokens in a repository for CI?
No. Treat the JSON as authentication material, keep it out of source control and provide it through protected CI storage.
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