How to get the Salesforce Instance Server URL from APEX Trigger?

Using trigger we can get the Salesforce Server URL, below is the example:

for example, used below codes in before insert or before update triggers from account object,

 trigger accountBeforeInsert on Account (before insert, before update) { if(trigger.isBefore == true && (trigger.isInsert == true || trigger.isUpdate == true)) { URL currentURL = URL.getCurrentRequestUrl(); URL comparisonURL = new URL(URL.getSalesforceBaseUrl().toExternalForm() + Page.YOUR_VF_PAGE_URL.getUrl()); system.debug('currentURL:::'+ currentURL); system.debug('comparisonURL:::'+ comparisonURL); boolean knownPath = currentURL.getPath() == comparisonURL.getPath(); if(knownPath == true) { // Currently You comming from Custom VF Page ("YOUR_VF_PAGE_URL") } else { // Currently You Comming from Standard Account Page Creation. } } } 

Note: if you view and submitting the page from “YOUR_VF_PAGE_URL” then you can get the values true in the “knownPath” variables.
Ex:
https://c.cs8.visual.force.com/apex/YOUR_VF_PAGE_URL?Id=00UL0000001Yyvh
knownPath = TRUE;

if you trying to create a new account from standard page
https://cs8.salesforce.com/001/e?retURL=%2F001%2Fo&nooverride=1
knownPath = FALSE;