Waits & Synchronization — Selenium WebDriver Automation | Sabaoon Academy

Modern web apps load content asynchronously. If Selenium tries to click an element before it exists, the test fails with NoSuchElementException. Waits tell Selenium to pause until a condition is met.

The Problem

driver.get("https://app.example.com/dashboard")
# ❌ fails if the table hasn't loaded yet
rows = driver.find_elements(By.CSS_SELECTOR, "table tbody tr")

Implicit Wait

driver.implicitly_wait(10)   # seconds — set once per session

Tells Selenium to poll the DOM for up to 10 seconds before raising NoSuchElementException. Simple, but applies globally to every find_element call — which can mask real bugs.

Explicit Wait (Preferred)

from selenium.webdriver.support.ui import WebDriverWait
from selenium.webdriver.support import expected_conditions as EC

wait = WebDriverWait(driver, timeout=10)

# Wait until element is visible
el = wait.until(EC.visibility_of_element_located((By.ID, "results")))

# Wait until element is clickable
btn = wait.until(EC.element_to_be_clickable((By.CSS_SELECTOR, ".submit-btn")))
btn.click()

# Wait for text to appear
wait.until(EC.text_to_be_present_in_element((By.ID, "status"), "Done"))

# Wait for URL to change
wait.until(EC.url_contains("/dashboard"))

Explicit waits target a specific element for a specific condition — much more precise.

Common Expected Conditions

Condition	Use when
`visibility_of_element_located`	Element must be visible
`element_to_be_clickable`	Element must be enabled and visible
`presence_of_element_located`	Element in DOM (may be hidden)
`text_to_be_present_in_element`	Text appears inside element
`url_contains`	URL changes after navigation
`staleness_of`	Old element is replaced by a new one

Wait Timing Visualiser

Async page load simulation

Ctrl+Enter

HTML

CSS

var rows = [
{ id: 1, name: 'Alice', status: 'Active' },
{ id: 2, name: 'Bob',   status: 'Inactive' },
{ id: 3, name: 'Carol', status: 'Active' },
];

document.getElementById('loadBtn').onclick = function() {
var log = document.getElementById('waitLog');
var loader = document.getElementById('loader');
var table  = document.getElementById('resultsTable');

table.style.display = 'none';
loader.style.display = 'block';
log.textContent = '';
this.disabled = true;

var ticks = 0;
var interval = setInterval(function() {
  ticks++;
  log.textContent = 'WebDriverWait polling… attempt ' + ticks;
  console.log('polling DOM for #resultsTable — attempt ' + ticks);
}, 400);

setTimeout(function() {
  clearInterval(interval);
  loader.style.display = 'none';

var tbody = document.getElementById('tbody');
  tbody.innerHTML = '';
  rows.forEach(function(r) {
    var tr = document.createElement('tr');
    tr.innerHTML = '<td>' + r.id + '</td><td>' + r.name + '</td><td>' + r.status + '</td>';
    tbody.appendChild(tr);
  });
  table.style.display = 'table';

log.textContent = 'visibility_of_element_located → condition met after ' + ticks + ' polls ✓';
  document.getElementById('loadBtn').disabled = false;
  console.log('element now visible — wait.until() returns element');
}, 1800);
};

Preview

Fluent Wait (Advanced)

from selenium.webdriver.support.ui import WebDriverWait

wait = WebDriverWait(
    driver,
    timeout=15,
    poll_frequency=0.5,                    # check every 500ms
    ignored_exceptions=[StaleElementReferenceException],
)
el = wait.until(EC.visibility_of_element_located((By.ID, "content")))

Use fluent wait when elements are expected to go stale (e.g., after a partial page re-render).