Handling JavaScript Alerts, Confirms and Prompts in Selenium

Browser-native alert, confirm and prompt dialogs are not part of the DOM — they are operating-system-level popups that Selenium cannot interact with using normal find_element calls. When an alert appears, Selenium must switch to it using driver.switch_to.alert before it can read the text, accept it, dismiss it, or type into it. If your test does not handle the alert, every subsequent Selenium command will throw UnexpectedAlertPresentException because the alert blocks all interaction with the page.

JavaScript Alerts, Confirms and Prompts #

There are three types of browser-native dialogs, each requiring slightly different handling.

from selenium import webdriver
from selenium.webdriver.common.by import By
from selenium.webdriver.common.alert import Alert
from selenium.webdriver.support.ui import WebDriverWait
from selenium.webdriver.support import expected_conditions as EC

# driver = webdriver.Chrome()

# ── Three types of JavaScript dialogs ──

DIALOG_TYPES = {
    "alert()": {
        "js_code": "alert('File saved successfully!')",
        "buttons": "OK only",
        "input_field": False,
        "handling": [
            "alert = driver.switch_to.alert",
            "text = alert.text           # Read: 'File saved successfully!'",
            "alert.accept()              # Click OK",
        ],
    },
    "confirm()": {
        "js_code": "confirm('Are you sure you want to delete?')",
        "buttons": "OK and Cancel",
        "input_field": False,
        "handling": [
            "alert = driver.switch_to.alert",
            "text = alert.text           # Read: 'Are you sure you want to delete?'",
            "alert.accept()              # Click OK (confirm)",
            "# OR",
            "alert.dismiss()             # Click Cancel (reject)",
        ],
    },
    "prompt()": {
        "js_code": "prompt('Enter your name:')",
        "buttons": "OK and Cancel",
        "input_field": True,
        "handling": [
            "alert = driver.switch_to.alert",
            "text = alert.text           # Read: 'Enter your name:'",
            "alert.send_keys('Alice')    # Type into the prompt",
            "alert.accept()              # Click OK (submit)",
            "# OR",
            "alert.dismiss()             # Click Cancel (reject, input ignored)",
        ],
    },
}


# ── Complete example: handle a confirm dialog ──
def handle_delete_confirmation(driver):
    # Click the delete button that triggers a confirm dialog
    delete_btn = driver.find_element(By.CSS_SELECTOR, "[data-testid='delete-btn']")
    delete_btn.click()

    # Wait for the alert to appear
    WebDriverWait(driver, 5).until(EC.alert_is_present())

    # Switch to the alert
    alert = driver.switch_to.alert

    # Read the alert text
    alert_text = alert.text
    print(f"Alert says: {alert_text}")
    assert "are you sure" in alert_text.lower()

    # Accept the confirmation (click OK)
    alert.accept()

    # After accepting, we are back to the main page
    # Verify the item was deleted
    WebDriverWait(driver, 5).until(
        EC.invisibility_of_element_located((By.CSS_SELECTOR, "[data-testid='item-row']"))
    )


# ── Handle an unexpected alert ──
def dismiss_any_alert(driver):
    try:
        alert = driver.switch_to.alert
        print(f"Unexpected alert: {alert.text}")
        alert.dismiss()
    except Exception:
        pass  # No alert present — continue normally


for dialog, info in DIALOG_TYPES.items():
    print(f"\n{'='*55}")
    print(f"  {dialog}")
    print(f"{'='*55}")
    print(f"  JS:      {info['js_code']}")
    print(f"  Buttons: {info['buttons']}")
    print(f"  Input:   {'Yes' if info['input_field'] else 'No'}")
    print(f"  Handling:")
    for step in info['handling']:
        print(f"    {step}")

Common Mistakes #

Mistake 1 — Using switch_to.alert on HTML modals #

❌ Wrong: A Bootstrap or Material UI modal dialog appears and the test calls driver.switch_to.alert — throws NoAlertPresentException.

✅ Correct: Inspect the dialog — if it is an HTML element in the DOM, use find_element to interact with its buttons. Only use switch_to.alert for browser-native dialogs created by window.alert().

Mistake 2 — Not waiting for the alert before switching #

❌ Wrong: button.click(); alert = driver.switch_to.alert — fails if the alert has not appeared yet.

✅ Correct: button.click(); WebDriverWait(driver, 5).until(EC.alert_is_present()); alert = driver.switch_to.alert