Also known as a layout without columns. There might be no problems for the most modern systems using the latest OCR techniques to determine separate columns of information. However, an ATS that uses older approaches will probably mesh all the text together and turn your well-prepared CV into gibberish. For example, if one side of the CV lists your experience and the other one skills – an ATS will be reading from left to right, line by line, and joining any text that comes in between, completely messing up the information flow. The one-column layout ensures that there won't be any such issues for any parsing techniques.