Compare two documents with AI

Who is this for?

You have two versions of the same thing and you need to know what changed. A contract and the copy someone sent back. A lease and the renewal. Two PDFs of a policy. Two Word drafts. Two Excel sheets that should have matched.

You do not need the chat to decide which version is better. You need a list of differences you can find with your own eyes.

What do you need before you start?

Gather the items below before you open the chat. You already have most of them.

• Both files, or the pages you care about
• A clear label for each one, such as "March draft" and "Friday draft"
• Permission to put that text in the chat you are about to use
• Ten quiet minutes to open the file and find two quotes yourself

What should you keep private?

Do not paste a confidential file into a personal ChatGPT, Claude, Gemini, Copilot, or Perplexity account because it is faster. If this is work, check your workplace policy first. Use the tool your company already approved. If the policy is "do not paste contracts into a personal chat," that is the end of this guide for that file.

Privacy: what not to paste

Before any paste, take out what the comparison does not need:

• Account numbers, routing numbers, and card numbers
• Government ID numbers and a full home address, if the question is about a clause and not about the address
• Passwords, signatures, and a medical detail
• A customer's or a coworker's private rows in a spreadsheet

A lease you signed is your document, and it is still private. Compare the clauses you are worried about. You do not need to paste the whole packet if one section is the fight. The wider do-not-paste list is Keep your data private with AI.

This page is not legal advice. AI cannot tell you whether a clause is fair or enforceable. It can show you words that differ. You decide what to do, and a lawyer is the right next person when the words move your money, your home, or your job.

When should you not use AI for this?

Some jobs should stay with you. If one of these is true, close the chat.

• The file is marked confidential and your work rule says it stays in a work system. Stop.
• The sheet is a full export of employees, students, patients, or customers. Compare a redacted sample, or do it inside the approved tool.
• You need a legal opinion. A difference list is not an opinion.
• You only have one document and you want a summary. Use Summarize a long report instead. Comparing needs two sides.

How do you say which file is which?

Give each version a name you will recognize later. "A" and "B" are fine if you also say what they are. Tell the chat the only source is the text you provide. It must not fill a gap from a "standard contract" it thinks it knows. Answer only from your sources is the rule.

If your account can take a file upload, and you are allowed to upload, you can attach the two PDFs or the two Word files instead of pasting. Free Gemini can read a file you upload. A chat with no upload button needs the paste. Either way, you still find the quotes yourself.

Compare two documents. Use only the text I give you. Do not use a "typical" contract, a law, or a guess to fill a hole.

Document A ([what it is, and the date if you know it]):
[paste A, or "I uploaded A"]

Document B ([what it is]):
[paste B, or "I uploaded B"]

Do not tell me which one I should sign.
List only real differences.
For each difference:
- Topic, in a few words
- Quote from A, copied from A. If A is silent, write A DOES NOT SAY.
- Quote from B, copied from B. If B is silent, write B DOES NOT SAY.
- Where I should look (page, heading, or the first words of the paragraph)

If you cannot copy the quote from my text, do not include that row.
Then stop.

For a lease or a renewal, add: "Pay extra attention to rent, the dates, who pays for repairs, the notice I must give before I leave, and any new fee. If one of those is not in the paste, write NOT IN THE PASTE. Do not guess the number."

How do you ask again in the shape of the file?

A PDF and a Word draft want quotes. A spreadsheet wants cells. Do not use the contract prompt on a sheet of numbers. The chat will invent a narrative around columns.

Two Word documents are the quote prompt above. If Word on your computer shows Compare on the Review tab, run it on the same two files. You are looking for a disagreement between Word and the chat. If they disagree, believe the file you have open, then sort it out. If the Review tab has no Compare command, skip that step. This site does not list a Microsoft price, and a missing button is not a prompt problem.

Two PDFs are the same quote prompt. Ask for a page number only if the PDF you uploaded has page numbers you can see. If the chat invents "page 14" and your file has 6 pages, that row is wrong.

Two Excel sheets, or two tabs, start smaller:

Compare these two sheets. Use only the cells I pasted. Do not invent rows.

Sheet A headers: [headers]
Sheet A rows:
[a few redacted rows, including one row whose total I already know]

Sheet B headers: [headers]
Sheet B rows:
[the matching rows]

Tell me which cells differ. Quote the cell as the header name and the value, from my paste.
If a header exists on only one sheet, say so.
Do not write a formula yet.
On this known row, the total should be [the total you calculated]. If your reading of the row disagrees, stop and say so.
Then stop.

If you need a formula after you understand the difference, go to Get an Excel or Sheets formula and test it on a row you already understand. If the Copilot button is inside your Excel, the in-app guide is Use Copilot in Excel. If the button is missing, stay in the free chat with a small paste. Do not upload the workbook to a personal account to get around a missing button.

How do you find the quotes in the file?

This is the step people skip, and it is the whole point. Open document A and search for the first quote. Open document B and search for its pair.

• If both quotes are there, keep the row.
• If one quote is not in the file, delete the row. Tell the chat which quote failed.
• If the quote is there but the meaning is the opposite of what the chat said, keep the quote and throw away the chat's summary of it.
• If the chat said A DOES NOT SAY, search A for the topic anyway. Silence is a claim too. Catch facts the AI made up covers a missing line the same way it covers a fake number.

Check at least two rows even when the first one is perfect. A clean first row does not make the rest true. On a long file, check the rows that move money, a date, or a duty. You can skim a comma. You cannot skim the rent.

I checked your list against the files.
These quotes are really there: [rows].
These quotes are NOT in the file: [rows]. Delete them.
Do not add new differences.
Give me the list again, using only the rows I said are real.
Then stop.

Check each phase before the next one is this pause. You do not negotiate, sign, or reply to the other side on a list you have not searched.

How do you check it before you use it?

Before you reply to a landlord, a vendor, or your boss, answer these out loud.

• Can I point to both versions and show another person the exact words?
• Did any number in my note come from the chat instead of the page? If yes, it is out.
• Am I about to forward the chat's summary, which might still contain a secret I meant to remove?
• Is this a decision a lawyer or a manager should see? The difference list can go with you. It is not a substitute for them.

A worked pass looks like this. You paste two short clauses, not a whole lease. A says "Tenant may end this lease with 30 days' written notice." B says "Tenant may end this lease with 60 days' written notice." A good row quotes both sentences and names notice period as the topic. A bad row says "B is stricter" and quotes nothing. You search the PDF for "30 days" and "60 days" before you email anyone. If "60 days" is not in B, the row is fiction.

What mistakes should you avoid?

These are the misses that waste the result. Skip them before you send anything.

Common mistakes

• Asking "which contract is better?" The chat will pick a side and sound like a lawyer. You asked for a comparison, not a verdict.
• Pasting the confidential original into a personal chat because the work account felt slow.
• Keeping a quote you did not search for, because the list was long and the meeting was soon.
• Comparing two Excel files by uploading every tab, including names and pay. Redact first. Test one known row.
• Letting the second draft put a deleted quote back in. Say "do not add that row again."

What should you check before you use it?

Answer each line below. If one is still a no, do not use the result yet.

Director check: look before you use it

• Is every difference a quote you found, or a silence you searched for? If not, it is not ready to forward.
• Did you follow the workplace rule before the paste? Speed is not permission.
• Did the known spreadsheet row match? If the total is wrong, do not trust the other cells.
• Are you treating this as legal, medical, or HR advice? Stop. Use the qualified person. Use the documents as the source they should read too.

What is one extra tip?

When the differences are real, write your reply from the quotes, in your own words. Write a letter is the path if you need to ask for one change. Summarize a long report is the path when you have one file, not two. A health-plan packet is that kind of one-file job, on Compare health plans with AI. You still do not paste a member ID.

One extra tip

More work guides are on Work. Research habits are on Research. Spreadsheet habits are on Spreadsheets.