If a Salesforce VF page using standard controller and extension both then which will fire first?

Hi,
Based on your formula field {! } it will execute the corresponding extension. If both the extension having same method name then it will execute the first extension. Below is the example

If both extensions having the same method, whichever methods are defined in the “leftmost” extension, or, the extension that is first in the comma-separated list will execute first.