Use Selenium’s CSS locator strategy by passing a CSS selector string to the language binding’s CSS locator API. For example, in Python, driver.find_element(By.CSS_SELECTOR, "#fname") finds an element whose ID is fname. The key is to choose a selector that matches the intended element and use the matching locator strategy; broad selectors can return the wrong element, while malformed or mismatched selectors can raise InvalidSelectorException.
How to find an element by CSS selector in Selenium
Start with the rendered DOM: identify the element and choose the smallest useful selector that distinguishes it from the other elements on the page. Selenium supports CSS selectors as a built-in WebDriver locator strategy. In Python, import By and pass the selector to find_element:
from selenium.webdriver.common.by import By
first_name = driver.find_element(By.CSS_SELECTOR, "#fname")Here #fname is CSS syntax for an element with the ID fname. Selenium’s locator documentation demonstrates this pattern and attribute-based selection: Selenium locators.
Write selectors for IDs, attributes, and classes
ID
CSS uses # before an ID value, so an element with id="fname" is selected with #fname. You can also use Selenium’s dedicated ID strategy. The ID strategy takes the raw ID value, without the hash:
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by_css = driver.find_element(By.CSS_SELECTOR, "#fname")
by_id = driver.find_element(By.ID, "fname")Use an ID only when it identifies the intended element in the page you are testing.
Attributes
CSS attribute selectors use square brackets. For example, to find an input whose name is newsletter:
newsletter = driver.find_element(
By.CSS_SELECTOR,
"input[name='newsletter']"
)Check the actual markup before choosing an attribute. Prefer a clear attribute that your application keeps meaningful; whether a particular attribute remains stable depends on the application.
Classes and element types
Use a dot before a class name, optionally combined with an element type or attribute. For example, input.information targets inputs with that class, while .information can match elements of any type. If the class appears on multiple elements, add a reliable condition or search within the relevant parent.
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Choose the right locator strategy
Selenium’s guidance recommends a well-written CSS selector when a unique ID is unavailable. A practical choice depends on whether the locator is clear, unique, maintainable, and able to express the relationship your test needs—not just on its length.
| Strategy | Example | When it fits |
|---|---|---|
| ID | By.ID, "fname" |
A suitable ID identifies the target. |
| CSS | By.CSS_SELECTOR, "input[name='newsletter']" |
A clear CSS selector identifies the target, particularly when no unique ID is available. |
| XPath | By.XPATH, "//input[@value='f']" |
The needed relationship or selection is better expressed with XPath. |
Selenium describes XPath as flexible but harder to debug and says it tends to be slow, while noting that browser vendors typically do not performance-test XPath selectors. Treat that as Selenium’s locator guidance, not a universal benchmark proving CSS is faster in every browser. Use the strategy your team can read and maintain consistently.
Handle selectors that match multiple elements
find_element returns the first matching element. If a selector is broad, that may not be the element the test intended. Use find_elements when you expect multiple matches; it returns all matches, or an empty list if none are found.
matches = driver.find_elements(By.CSS_SELECTOR, ".information")
if not matches:
raise AssertionError("No elements matched .information")If the test needs a particular match, tighten the selector or search from a suitable parent rather than relying on document order.
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Search from a parent element
A WebElement can be used as the search context for its descendants. First locate the relevant parent, then search within it:
form = driver.find_element(By.CSS_SELECTOR, "form#signup")
email = form.find_element(By.CSS_SELECTOR, "input[name='email']")This limits the search to descendants of that form; it does not make an otherwise ambiguous selector unique if there are still several matching descendants.
Find elements inside a shadow root
A normal page-level CSS lookup does not automatically cross a shadow DOM boundary. Locate the host, obtain its shadow root, and search within that root. Selenium documents these shadow-root methods for Selenium 4.0 and later and discusses browser support in relation to Chromium 96; check the current support of the browser and driver used by your test.
host = driver.find_element(By.CSS_SELECTOR, "my-widget")
shadow_root = host.shadow_root
button = shadow_root.find_element(By.CSS_SELECTOR, "button.save")The selector in the final line is evaluated inside the shadow root, not against the whole document. See Selenium’s element finder documentation.
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Use the CSS locator API in other language bindings
The locator syntax remains CSS, but the binding’s method and constant vary. In Java, Selenium uses By.cssSelector:
WebElement firstName = driver.findElement(By.cssSelector("#fname"));In Selenium’s JavaScript binding, the CSS locator is written with By.css:
const firstName = await driver.findElement(By.css('#fname'));Use the API and import conventions for the Selenium binding and version in your project; do not send a selector from one strategy through another strategy’s locator method.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Fix InvalidSelectorException and selectors that find nothing
InvalidSelectorException
This exception commonly points to invalid selector syntax or a mismatch between the selector language and the locator strategy. Check the selector and the call together:
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- Check punctuation, brackets, quotes, and spelling. A missing closing bracket or malformed selector can make CSS invalid.
- Send CSS through
By.CSS_SELECTOR, XPath throughBy.XPATH, and a raw ID throughBy.ID. - Do not pass XPath such as
//input[@value='f']to a CSS locator, or CSS such as#fnameto an XPath or ID locator. - Inspect the rendered DOM to confirm the tag, ID, class, or attribute used by the selector.
Selenium’s error guidance identifies invalid syntax and using a selector with the wrong locator strategy as common causes: Selenium troubleshooting errors.
Valid selector, no matching element
No match is different from invalid syntax. If Selenium does not find an element, check whether the page has reached the expected state, whether the element exists in the current DOM, and whether the lookup is being made from the right context. A correct selector evaluated before the page renders the target can still return no match.
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Frequently Asked Questions
Can a CSS selector contain XPath syntax?
No. CSS and XPath are separate selector languages; pass each through its corresponding Selenium locator strategy.
Quick Recap
What does find_elements return when there is no match?
It returns an empty list.
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