Evaluate and validate XPath/CSS selectors in Chrome Developer Tools

Published: by Creative Commons Licence

Google Chrome provides a built-in debugging tool called "Chrome DevTools" out of the box, which includes a handy feature that can evaluate or validate XPath/CSS selectors without any third party extensions.

This can be done by two approaches:

  • Use the search function inside Elements panel to evaluate XPath/CSS selectors and highlight matching nodes in the DOM.
  • Execute tokens $x("some_xpath") or $$("css-selectors") in Console panel, which will both evaluate and validate.

From Elements panel

  1. Press F12 to open up Chrome DevTools.
  2. Elements panel should be opened by default.
  3. Press Ctrl + F to enable DOM searching in the panel.
  4. Type in XPath or CSS selectors to evaluate.
  5. If there are matched elements, they will be highlighted in DOM.
    However, if there are matching strings inside DOM, they will be considered as valid results as well. For example, CSS selector header should match everything (inline CSS, scripts etc.) that contains the word header, instead of match only elements.

Evaluate XPath/CSS selectors using 'Elements' panel's seach function

From Console panel

  1. Press F12 to open up Chrome DevTools.
  2. Switch to Console panel.
  3. Type in XPath like $x(".//header") to evaluate and validate.
  4. Type in CSS selectors like $$("header") to evaluate and validate.
  5. Check results returned from console execution.
    • If elements are matched, they will be returned in a list. Otherwise an empty list [ ] is shown.

    $x(".//article")
    [<article class="unit-article layout-post">…</article>]

    $x(".//not-a-tag")
    [ ]

    • If the XPath or CSS selector is invalid, an exception will be shown in red text. For example:

    $x(".//header/")
    SyntaxError: Failed to execute 'evaluate' on 'Document': The string './/header/' is not a valid XPath expression.

    $$("header[id=]")
    SyntaxError: Failed to execute 'querySelectorAll' on 'Document': 'header[id=]' is not a valid selector.

Evaluate XPath/CSS selectors using 'Console' panel

Pros and cons

Advantages of one approach are pretty much considered as the cons of another method, and vice versa.

From 'Elements' panel From 'Console' panel
Pros Cons
Quick and easy accessibility Need to switch panel and extra typing
Results are directly highlighted in DOM Results are shown in a list
Need to right click and go back to 'Element' panel
Result count is displayed Only a list of matching nodes are displayed
Cons Pros
All matched strings are also counted in Will only match elements
Only evaluates, doesn't validate
Invalid locators will just return nothing
Throw exceptions if locator is invalid
- Can be used in console immediately for other purposes