Plagiarism checker tools are online software or applications designed to detect and identify instances of plagiarism in written work. These tools typically compare the text of a document against a vast database of existing sources, including online articles, books, and academic papers, to identify any similarities or matching phrases.

Plagiarism checkers typically operate in two ways: first, by comparing the submitted text against the database of existing sources, and second, by using advanced algorithms to identify instances of paraphrasing, where the author has used different words to express the same ideas as another source. Some plagiarism checkers also offer additional features, such as the ability to check for grammar and spelling errors or to provide suggestions for improving the writing style.

Plagiarism checker tools are widely used by students, academics, journalists, and other professionals to ensure that their work is original and free from any instances of plagiarism. They can also be used by publishers and editors to verify the authenticity of submitted manuscripts before publication.

While plagiarism checker tools can be highly effective in detecting instances of plagiarism, they are not foolproof and may occasionally produce false positives or fail to detect certain types of plagiarism. As such, it is still important for writers and authors to carefully review and edit their work to ensure its originality and authenticity.