ChatGPT vs Claude vs Copilot in Excel: where your file goes, and how you undo a change

Where does my workbook go when I ask each AI a question?

A bit of background helps clear this up. None of these tools does the thinking inside your PC. When you type a prompt, the part of your workbook the tool reads goes to a model running in a data centre, and the answer comes back to your screen. The important part is knowing which company runs that data centre and which agreement covers your file.

Copilot is built by Microsoft, so your data goes to Microsoft. On a work or school account, Microsoft’s enterprise data protection page says Copilot falls under the Data Protection Addendum (DPA), which means Microsoft acts as a data processor, handling your file only on your instructions. That same page says your prompts, responses and the data Copilot reads aren’t used to train foundation models, which are the big general models behind it.

The terms are worded differently on home plans, but the training answer stays the same. Microsoft’s page on Copilot in Microsoft 365 apps for home covers Personal, Family, Premium and Pro plans, and it says your prompts, responses and file contents aren’t used to train foundation models. It also says Copilot looks at the file you are working in, plus any other file you ask it to look at.

The other two tools work as add-ins. ChatGPT for Excel and Claude for Excel are apps from outside Microsoft that run in a side panel inside Excel, and you sign in to them with your ChatGPT or Claude account. Whatever they read goes to OpenAI or Anthropic under the rules of that account, and your Microsoft contract does not cover it.

I went through every setting on the ChatGPT side in is ChatGPT for Excel safe for client files, including the 30 day logs OpenAI says it may keep. I read OpenAI’s help page for the add-in again on 19 October, and it still says your data is stored locally in the product and that you can delete it in the add-in’s Settings.

Is Claude inside Copilot the same as the Claude for Excel add-in?

This is where most comparisons get confused, because they talk about Claude as if it were one thing. You can now reach Claude models inside Excel in two completely different ways, and your data takes a different route depending on which one you choose.

The first way is through Copilot itself. On a commercial Copilot plan or Microsoft 365 Premium, Copilot in Excel has a model picker where Claude can be one of the choices. Microsoft’s page on Anthropic models in Microsoft Online Services explains that Anthropic works there as a Microsoft subprocessor, meaning a company Microsoft hires to handle your data under Microsoft’s own contract. The Microsoft Product Terms and the DPA still apply, and so does enterprise data protection.

That same page lists an exception that matters if you work with European clients. Anthropic models are currently excluded from the EU Data Boundary, which is Microsoft’s promise to keep EU customers’ data processed inside the EU. That is why Microsoft switches them off by default for organisations in the EU, EFTA and the UK. Some newer models are labelled “Anthropic models with Data Retention”, and for those Anthropic stores most inputs and outputs for up to 30 days under its own terms, so an admin has to opt in to them separately.

The second way is Anthropic’s own add-in. You sign in to this panel with your Claude account, and Anthropic’s Claude for Excel page says inputs and outputs are deleted on its backend within 30 days, except in the cases it lists. Your chat history stays in your browser rather than on Anthropic’s servers. The same page also says the add-in does not inherit custom retention settings your organisation may have set, and its activity is not in Enterprise audit logs.

I wrote down why Claude might not show up in your model picker, along with the exact admin setting to ask for, in why Claude is missing from the Copilot model picker in Excel. What the add-in itself can and cannot do inside a workbook is in Claude in Excel is good with formulas and blind to your macros.

Which one changes my cells, and does it ask first?

All three can now edit a workbook instead of only answering about it. They can build new sheets, change values, sort and filter. The real difference is the default, meaning what happens when you send a prompt without thinking about the setting.

Copilot starts in Allow editing. Microsoft’s Agent Mode in Excel page describes three modes, and because Copilot opens in edit mode by default, it acts on your request straight away. If you only want an answer, you have to switch to Chat only before you type, or to Plan if you want to see the steps first and confirm them.

The two add-ins lean the other way. OpenAI’s launch post for ChatGPT for Excel says it asks for permission before it changes your workbook, and it points its answers back to the cells it used. Anthropic says Claude for Excel warns you before it overwrites existing data, and asks you to confirm before a risky operation.

A confirmation box only helps if you read what it says. Anthropic is very direct about this, because its own testing found that a spreadsheet from outside, with hidden text inside it, could push the add-in into changing or extracting data if it acted without verification. When you work on a file someone else sent you, take a second to read every box instead of clicking through quickly.

I use the same routine with all three tools. I ask my question first, read the answer, and only then let the tool make one change I can name. I wrote out that order for Copilot in stop Copilot changing your Excel file. I follow the same order with the add-ins, and the confirmation box is my last check, not my first.

How do I undo a change each AI made in Excel?

Undoing a change is where these three tools differ the most. It comes down to who made the edit and what record Excel keeps of it.

Edits made by Copilot are Excel’s own, so Excel keeps a record of them. Microsoft’s change history page says you can ask Copilot “What changes has Copilot made to this workbook?”, and Excel keeps supported changes for up to 365 days. Neither add-in has a question like that you can ask about past edits.

People often check Show Changes on the Review tab next, but Microsoft’s own help page admits a gap in it. When a cell is edited through code, and Microsoft gives an add-in as an example, the record can keep the new value but lose the old one. That means you can see that a cell changed, but not what was in it before. I explain how that happens in what Copilot change history in Excel can and cannot see, and Show Changes also never records formatting, charts or PivotTables, whoever made the change.

Version History brings back the whole earlier file for any of the three, but only when the workbook is saved on OneDrive or SharePoint. A workbook on your desktop or a USB stick has no Version History. That is why OpenAI tells you to duplicate the file first for important work, and why Anthropic’s best practice list says to start with a trusted copy before asking Claude to edit widely.

1. 01
   Make the copy before the first prompt

   Save As with a new name, or check the file is on OneDrive or SharePoint so Version History exists.
2. 02
   Undo small changes straight away

   Ctrl+Z is fine for one change you notice right away. For a job that touched several sheets, do not try to count your way back.
3. 03
   With Copilot, ask what changed

   Type "What changes has Copilot made to this workbook?" and compare it with what you expected.
4. 04
   With an add-in, compare against your copy

   Check one total in the copy and in the edited file. If they differ and you did not ask for that, go back to the copy.

That last check is where you catch the real mistakes, because a total can look completely right and still be wrong. The five minute check I use is in how to check if ChatGPT or Copilot got your Excel numbers right, and I use it no matter which AI edited the sheet.

Which plan do I need for ChatGPT, Claude and Copilot in Excel?

Your plan matters for two reasons. It decides whether you can use the tool at all, and on the add-ins it also decides the training default. So the same side panel can follow different rules depending on the account you signed in with.

A quick example shows why this matters. If your office runs Excel 2019 on a volume licence, Claude for Excel will not install at all, and buying a Claude plan changes nothing. And if you share workbooks with people on older Excel, the formulas these tools write can break on their end too, which I covered in Office 2021 support ended: your Excel still works, but newer formulas show #NAME?.

So which AI should I use on a client's Excel file?

There is no single tool that fits every situation, but the client’s contract usually decides it before the features do. Here is how I would choose in three common situations.

If you are working inside a client’s own Microsoft 365, on their account, use Copilot. That keeps the file under the agreement your client already signed with Microsoft. If the client is in the EU or the UK and you want Claude in the model picker, talk to their admin first, because of the EU Data Boundary point in section 02.

If you are a freelancer, the client emailed you the file, and you have a personal ChatGPT or Claude plan, either add-in can do the job. Turn the training setting off first (Improve the model for everyone in ChatGPT, Model Improvement in Claude’s privacy settings), and work on a copy. Anthropic’s Excel page does not say whether that setting covers the add-in, so I turn it off anyway. And if the contract says the data stays with the client, ask the client before you open their file with any add-in at all.

If the workbook does its real work in macros, none of the three is a good fit. Anthropic lists macros and VBA as unsupported, OpenAI says they may not be fully supported, and Copilot does not offer macro editing. There, I would use the AI to explain the formulas around the macro and leave the VBA to a person.