How to See What Changed Between Two Versions

Someone sends back "the contract with a few small changes." Finding those changes is now your problem, and the usual method, two windows, scrolling in parallel, is exactly how a changed number gets missed.

Pixels lie about change

The intuitive way to compare two documents is to overlay them and highlight the differences. It works on a poster. On a contract it fails immediately: insert one word in the second paragraph and every line after it shifts. A pixel comparison dutifully reports that ninety percent of the page changed, which is true and useless.

Comparing words asks the question a reader is asking. One word inserted is one word added, and the reflowed lines below it are not changes at all.

What that looks like in practice

A lease where the rent moved from 1,200 to 1,350 and the due date from the first to the fifth reports exactly that: two removals, two additions, one page affected. Not "page 1 differs."

The honest limits

Word comparison cannot see everything, and a tool that implied otherwise would be dangerous:

• Formatting is invisible. A clause moved to a smaller font, or greyed out, reads as unchanged. The words are the same.
• Images are not compared. A swapped signature block or altered exhibit will not be flagged.
• Scans cannot be compared at all. No text layer, nothing to diff. Both files must be text-based.
• Inserted pages shift everything. A page added near the front makes all later pages appear changed. The page-count difference is reported so you can see why.

For contracts and policies the words carry the obligations, so this covers the risk that matters. For design proofs it is the wrong tool entirely.

A workflow that catches things

1. Compare, and read the summary before the detail. "Three pages changed, 40 words added" sets your expectation.
2. If the page count changed, resolve that first. It explains most apparent differences.
3. Read the additions before the removals. New obligations are usually what was added.
4. Check numbers and dates by eye regardless. They are short, easy to miss in a wall of text, and the most expensive to get wrong.