The majority of plagiarism detectors can check for plagiarism in languages other than English; however, their performance varies. This is because plagiarism detectors compare your text against databases of existing works, so results are generally better when there is strong representation of content in that language, such as Spanish, French, or German. For languages with fewer resources, however, coverage is likely to be poorer.
A common case to consider is translation plagiarism, which occurs when text is copied from a source in a foreign language and then translated. Most detectors fail to identify similarities across languages. If you write in a language other than English, make sure you run the check in the language of the original source. Learn how the technology works in our post on what is a plagiarism test, and run your text through the Plagiarism Checker.