Similarity checking.
WHAT THEY DO
Compare submitted work against sources and other submissions, reporting matching text.
WHAT A MATCH INDICATES
Similarity, not necessarily plagiarism.
WHAT MATCHES LEGITIMATELY
Properly quoted material References Common phrases Technical terminology
WHAT A REPORT REQUIRES
Human judgement, not a threshold.
WHAT TO DO IF YOU HAVE ACCESS BEFORE SUBMISSION
Check your own work Examine every match Correct anything inadequately attributed
WHAT NOT TO DO
Attempt to evade detection by altering wording Use tools that rewrite text to avoid matching
WHY
That is an attempt to conceal plagiarism, and is treated more seriously than plagiarism itself.
WHAT TO UNDERSTAND
The tool identifies matches. The judgement of misconduct is made by people.
WHAT REDUCES LEGITIMATE MATCHES
Paraphrasing properly Quoting sparingly Writing in your own voice
WHAT TO DO ABOUT A HIGH SIMILARITY SCORE WITH PROPER ATTRIBUTION
Nothing. It may simply reflect extensive quotation, which is a writing issue rather than an integrity one.