Instantly Check The Difference Between Two Files
diffChecker is a free online tool that you can either upload your text to or cut and paste your text to check.
WinMerge is a free and simple tool you can download if you prefer to not use a online tool. WinMerge will compare both files and folders for differences.
ExamDiff is another freeware tool you can download and use to compare files, folders and other formats using various plug-in’s making it very configurable.