Element Locators in Selenium

Element locators tell selenium which HTML element a command refers to.
Format of element locator is:
locatortype = argument

1. Locating by identifier
identifier = id
Selects an element with specified @id attribute.If no match is found, it will take the element with @name = id.

2. Locating by Name
name = name
Selects the first element with specified @name attribute. If multiple elements have the same value for a name attribute, then you can use filters to further refine your location strategy (matching the value attribute).

3. Locating by id
id = id
Selects the element with @id attribute.

4. Locating by DOM
The Document Object Model represents an HTML document and can be accessed using JavaScript.
dom = javascriptExpression
Example:
dom=document.forms['myForm'].myDropdown

5. Locating by XPath
xpath = xpathExpression
Locates an element with XPath expression.

XPath is the language used for locating nodes in an XML document. As HTML can be an implementation of XML (XHTML), Selenium users can leverage this powerful language to target elements in their web applications.
One of teh main reasons for using XPath is when you don't have a suitable id or name attribute for the element you wish to locate. You can use XPath to either locate the element in absolute terms, or relative to an element that does have an id or name attribute.
Absolute XPaths contain the location of all elements from the root and as a result are likely to fail with only the slightest adjustment to the application.
In Relatiion XPath, we can find a nearby element with an id or name attribute (ideally a parent element), you can locate you target element based on the relationship. This is less likely to change and can make your tests more robust.

Since only xpath locators start with "//", it is not necessary to include the xpath=label when specifying an XPath locator.

Example:
xpath=//img[@alt='The image alt text']
xpath=//table[@id='table1']//tr[4]/td[2]
xpath=//a[contains(@href,'#id1')]

6. Locating Hyperlinks by link Text
link = textPattern
Selects a link with specified text. If two links with the same text are present, then the first match will be used.

7. Locating by CSS
CSS (Cascading Style Sheets) is a language for describing the rendering of HTML and XML documents. CSS uses Selectors for binding style properties to elements in the document. These selectors can be used by Selenium as another locating strategy.
css = cssSelectorSyntax

8. ui = uiSpecifierString

Without an explicit locator prefix, selenium uses the following default strategies:
1. dom, for locators starting with document.
2. xpath, for locators starting with //