Pass and pen. Com are well-known duplicate checking websites, but the algorithm and comparison database are different, so it is impossible to directly compare which website is stricter.

The detection algorithm of PaperPass is strict. It compares papers with Internet resources and detects repeated characters more strictly. The algorithm of penpen network is relatively loose, mainly comparing the paper with HowNet database, and detecting repeated characters is relatively loose.

So we can't simply answer which website is more strict, it depends on the specific comparison database and algorithm. If accurate duplicate checking results are needed, it is best to use the duplicate checking system designated by the school or institution for testing.