Sometimes the tools called paraphrasing tool, why it is so called? As the tool use the logic of changing words according to its synonyms to make an article unique and meaningful. If we expand the main logic behind the tool use the word synonyms of targeted article that you will rewrite or spin, giving you the options to replace the word from its dictionary suggested by the boot as well as option to write your own, it’s simple but it’s superb.
Language claimed in HTML meta tag should match the language actually used on the web page. Otherwise Spinnerchief.com can be misinterpreted by Google and other search engines. Our service has detected that English is used on the page, and it matches the claimed language. Our system also found out that Spinnerchief.com main page’s claimed encoding is utf-8. Use of this encoding format is the best practice as the main page visitors from all over the world won’t have any issues with symbol transcription.
Imo it is not possible for google to detect properly spun content, it is not worth computing power it requires. They can do this using ngrams for example, but it is uses a lot of queries. And for example article spinner I coded beats this algo, so google cant detect that the content is spun. Manual spinning is also good but it takes more than 30 minutes per article.