Cookies, storage and session reuse

Read and write cookies, work with local and session storage, and save an authenticated session so most tests skip the login form.

Cookies

# you must be on the domain before touching its cookies
driver.get("https://app.example.com")

print(driver.get_cookies())
print(driver.get_cookie("session_id"))

driver.add_cookie({
    "name": "feature_flags",
    "value": "new-checkout",
    "domain": "app.example.com",
    "path": "/",
})

driver.delete_cookie("feature_flags")
driver.delete_all_cookies()

• Adding a cookie requires you to be on a page of that domain first; otherwise the browser rejects it silently.
• A cookie written with a domain you do not control will not be stored, and Selenium does not raise an error.
• delete_all_cookies() is the cheapest way to guarantee a test starts logged out.
• Cookies set with HttpOnly are still visible to WebDriver, which is a good reason to keep session material out of test logs.

Local and session storage

driver.execute_script("return localStorage.getItem('theme');")
driver.execute_script("localStorage.setItem('theme', 'dark');")
driver.execute_script("return Object.keys(localStorage);")
driver.execute_script("localStorage.clear();")

# session storage is cleared when the tab closes
driver.execute_script("return sessionStorage.getItem('draftId');")

# grab everything as a dictionary
snapshot = driver.execute_script("""
    const out = {};
    for (let i = 0; i < localStorage.length; i++) {
        const k = localStorage.key(i);
        out[k] = localStorage.getItem(k);
    }
    return out;
""")

Saving and reusing a session

import json, pathlib, time
from selenium import webdriver

STATE = pathlib.Path("state/auth.json")

def login_and_save(driver, base_url):
    driver.get(base_url + "/login")
    driver.find_element(By.ID, "email").send_keys("qa@example.com")
    driver.find_element(By.ID, "password").send_keys("secret")
    driver.find_element(By.ID, "submit").click()
    WebDriverWait(driver, 10).until(
        lambda d: "/login" not in d.current_url
    )
    # give the app a moment to persist its token
    WebDriverWait(driver, 10).until(
        lambda d: "session_id" in {c["name"] for c in d.get_cookies()}
    )
    STATE.write_text(json.dumps({
        "cookies": driver.get_cookies(),
        "origin": base_url,
        "saved_at": int(time.time()),
    }))

def restore(driver, state):
    driver.get(state["origin"])
    for cookie in state["cookies"]:
        cookie.pop("sameSite", None)     # some drivers reject this key
        cookie.pop("expiry", None)
        driver.add_cookie(cookie)
    driver.refresh()

1. Authenticate once in a session-scoped fixture and write the state to a JSON file.
2. Reuse that file in every test that is not about authentication.
3. Keep a small number of tests that do exercise the real login flow - they are your early warning when the mechanism changes.
4. Store credentials in the environment, never in the state file or the repository.
5. Treat the state file as a secret: it contains a live session token.

FAQ

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Last refreshed 2026-09-18.