They sent it back saying they “cleaned up a few typos.” Put both versions in and see precisely what moved: every changed amount, every shifted deadline, every clause that quietly appeared. Both documents are read by this tab and never leave your device.
Add both versions of the agreement.
Your contract stays on your machine. Free online diff checkers upload the document to a server. For an agreement under NDA that is the whole problem, not a footnote. Here the file is read by JavaScript in your tab: the comparison runs on your device and nothing is transmitted.
The flags are patterns, not judgement. REDLINE looks for the shapes of change that repeatedly matter: an amount or percentage that moved, a date or period that shifted, and inserted language like indemnity, hold harmless, sole discretion, unlimited liability, non-compete, arbitration, auto-renewal and jurisdiction. It cannot tell whether a change is good or bad for you, and it will both miss things and flag harmless edits. It decides what you read first. It is not legal advice, and it is not a substitute for a lawyer on anything that matters.
Every change is shown. The flag list is a reading order, not a filter: the full comparison underneath contains everything, so a change that tripped no rule is still there in front of you.
What it can read. Word .docx, PDF, plain text and Markdown, or text pasted directly. Old .doc files cannot be opened in a browser: re-save as .docx or PDF. A scanned PDF is a photograph of a page: it contains no text, so there is nothing to compare without OCR, and REDLINE will say so rather than show you an empty result.
PDF text is approximate. Text extracted from a PDF depends on how the file was produced. Column layouts, headers and footnotes can come out in an order that differs from what you see on the page. Where you have the .docx, use it.