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Claude For Comparing Documents

By Nigel Guy · 2 min read

Two versions of a contract, three vendor quotes, a revised draft against the original — the default move is to paste both in and ask "what changed?" or "which is better?" and take whatever comes back at face value, because reading two long documents side by side yourself is exactly the tedious work you were hoping to skip. The trouble is that a vague comparison request gets a vague comparison answer, and the differences that actually matter can be a single clause buried in ten pages of boilerplate that read identically.

The mechanism

1. Name the dimensions that matter before you ask. For contracts: price, term length, termination rights, liability caps. For quotes: unit cost, delivery time, what's excluded. A generic "compare these" produces a generic summary; a scoped one produces something you can act on.
2. Ask for changes as a list, tied to location. "What changed, by section" is more checkable than a prose summary — you want to be able to go back to the actual document and verify each claim, and a flat paragraph doesn't tell you where to look.
3. Ask explicitly what's the same. People ask what changed and skip what didn't — but confirming that the liability clause is genuinely unchanged is often as important as flagging what moved, especially in a contract you're about to sign.
4. Ask what's missing from one side, not just what differs. A clause present in version one and simply absent from version two is a different kind of change from a reworded one, and it's the one a straightforward diff-style question is most likely to undersell.
5. Verify anything load-bearing against the source documents yourself. Treat the comparison as a map to where to look, not as the final word on what the documents say.

What to skip

Skip asking for a single "which one is better" verdict on anything with real stakes — a contract or a quote has several axes that trade off against each other, and collapsing them into one recommendation hides the trade-off you actually needed to see. Skip pasting in scanned or badly formatted text and trusting the comparison at face value; garbled input produces a comparison that's confidently wrong in ways that are hard to spot.

Guardrails

• For anything legally or financially binding, a document comparison from Claude is a first pass that narrows what a person — often a professional — needs to check, not a substitute for that check.
• Long documents can exceed what fits usefully in a single pass; if a comparison feels thin on a long document, verify it isn't quietly working from a partial read.
• Numbers pulled from a comparison (totals, percentages, calculated differences) deserve the same verification as any other number Claude gives you — read them against the source before you act on them.

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