What is the best practice to create a unique url for every user profile
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In my every application i want to create a unique url for users profile as http://app.com/username .

I have the name of user is : 'Vijay Kumbhar' i can create http://app.com/vijay_kumbhar, but if there is another user registers with the same name then what will be better way of creating url for that user. 
 one way is to add vijay_kumbhar_1, but i dont think this is the proper way of creating a unique url 

Can you please suggest me the better way of doing this.