regex atlas
paste a pattern. see what it matches, what every piece means, and where it'll bite you.
/ /

test string

edit freely — matches update as you type

matched against your text

matches

replace

result


        

      

    


    

      

        
flags in effect

      

      


      

        
breakdown

      

      


      

        cheatsheet
        

      

    


  


  

    field exercises
    

      Write a pattern that matches every should match line and none of the
      should not match lines below it. Checked live, safely — same catastrophic-backtracking guard
      as the matcher above.