What is Custom XML Data in Excel?

Ever opened an Excel file and been greeted by a cryptic message about "Custom XML Data"? It’s one of those little quirks in Excel that can make you pause, wondering if your file is broken or contains something it shouldn’t. In most cases, it’s nothing to worry about, but understanding what it means can save you future headaches. This guide will walk you through exactly what Custom XML Data is, why it's in your spreadsheet, and how you can manage it.

First, A Super-Quick Primer on XML

Before we can talk about "Custom XML Data," we need to understand the XML part. Don't worry, this won't get too technical. XML stands for eXtensible Markup Language. The easiest way to think about it is as a universal language for structuring data that both humans and computers can easily understand.

Think about how a web page uses HTML tags to give content meaning. The <h1> tag tells the browser "this is a major heading," and the <p> tag says "this is a paragraph." HTML has a predefined set of tags you can use.

XML works in a similar way, using opening and closing tags to wrap around data elements. The key difference is that with XML, you get to create your own tags to describe your data. For example, if you wanted to store information about a customer, your XML might look something like this:

<customer id="123">
  <firstName>Jane</firstName>
  <lastName>Doe</lastName>
  <orders>
    <order>
      <orderId>A456</orderId>
      <total>99.99</total>
    </order>
  </orders>
</customer>

See how readable that is? You immediately know what each piece of information represents. This flexibility makes XML extremely useful for different applications to exchange information without misunderstandings. One app can package up its data in an XML file, and another app can receive it and know exactly how to interpret the contents.

So, What Does This Have to Do with Excel?

Now, let's connect this back to your spreadsheet. A modern Excel file (a .xlsx file) isn’t just a single document, it’s actually a zip archive containing a bunch of folders and XML files that define everything inside - the cell values, formatting, charts, and more.

Custom XML Data is extra information, structured using XML, that gets embedded within your Excel file by another application or process. It's "custom" because its structure isn't part of the standard Excel format, it’s defined by an external source to meet a specific goal. This data is typically invisible - you won’t see it in a cell or on a chart. It lives in the background, a passenger within your workbook.

Where Does Custom XML Data Come From?

• SharePoint Integration: If your Excel spreadsheet is linked to a SharePoint list, custom XML data is used to store information about that connection, like the location of the list and how the columns are mapped.
• Third-Party Add-ins: Many Excel add-ins (especially for business intelligence, data analysis, or reporting) need a place to save their settings or configuration data. Embedding it as custom XML in the workbook means the settings travel with the file.
• Custom Business Applications: Companies often have internal systems (like ERPs or CRMs) that generate or interact with Excel reports. These systems might embed custom XML to store metadata about the report, such as the report ID, the date it was generated, or the parameters used.
• Power Query (Less Common Now): In some older or specific scenarios, Power Query used to store certain connection information as custom XML, though this is less prevalent in modern versions of Excel.

The "Privacy Warning" Message: Why Excel Cares

You most often become aware of Custom XML Data when you try to save a workbook and Excel presents this message:

“Privacy warning: This document contains macros, ActiveX controls, XML expansion pack information, or web components. These may include personal information that cannot be removed by the Document Inspector.”

This sounds a bit alarming, but what it really boils down to is a "better safe than sorry" notification. Excel knows that another application has tucked some extra information into the file. However, it doesn't know what that information is.

From Excel’s point of view, that custom XML could include:

• Your username
• Server names or paths
• Database connection strings
• Other potentially sensitive metadata

Since Excel can't vet the contents for personal information, it warns you before you save or share the file. In 99% of cases, the data is benign and necessary for a feature to work properly. For example, it might just be <settings><color>blue</color></settings>. But because the possibility of it containing sensitive data exists, you get a heads-up.

How to Find and Remove Custom XML Data

After seeing the privacy warning, your first question is probably, "Should I remove it?" And the answer is a classic: it depends.

• Keep it if: The file is part of a managed process. If the spreadsheet gets its data from SharePoint or is used by a specific add-in, removing the XML could break that link or reset the add-in's configuration. The functionality might fail the next time you try to refresh the data or use the tool.
• Remove it if: You're about to share the workbook with someone outside your organization and you want to ensure the file is as clean as possible. Or, if the feature that originally created the XML is no longer needed (e.g., you've decommissioned an old add-in).

If you've decided to remove it, you can use Excel's built-in Document Inspector. This is a handy tool for scrubbing a file of hidden data and personal information before sharing.

Before you begin: Save a copy of your file! Removing custom XML could permanently break functionality, and there's no "undo" button. It’s always safer to work on a duplicate.

Step-by-Step Guide to Using the Document Inspector

1. With your workbook open (remember, a copy is best!), navigate to the File tab.
2. Select Info from the left-hand menu.
3. Click the Check for Issues button, and then choose Inspect Document from the dropdown menu.
4. The Document Inspector window will appear. It can check for many different types of hidden data. Ensure that the checkbox for Custom XML Data is checked. You can uncheck the others if you only want to focus on XML.
5. Click the Inspect button at the bottom.
6. After a few seconds, the Inspector will show its results. If it finds anything, you'll see a '!' icon and a Remove All button next to "Custom XML Data."
7. Click Remove All. This will strip all the custom XML parts from the workbook. Close the Document Inspector window.
8. Save your file to finalize the changes.

The warning message should now be gone because the data that was triggering it has been removed.

Practical Example: SharePoint List

To help make this less abstract, let’s imagine a real-world scenario. Your team uses a SharePoint site to track customer support tickets. You’ve used the “Export to Excel” feature in SharePoint to create a live, refreshable link to that list in a spreadsheet. Your team uses this spreadsheet to build pivot tables and charts for a weekly report.

In this case, SharePoint embeds custom XML data into the .xlsx file. This XML contains key information like:

• The URL of the SharePoint site.
• The unique ID of the list you’re connected to.
• Details about how the list columns map to the spreadsheet columns.

When you open your Excel file and click “Refresh All,” Excel looks at this embedded custom XML data to know where to find the newest data from SharePoint.

Now, if a team member unfamiliar with the process sees the privacy warning, opens the Document Inspector, and clicks "Remove All" next to Custom XML Data, they have unknowingly severed the connection. The next time someone tries to refresh the ticket data, it will fail with an error because Excel no longer knows where to look. They'll have to set up the connection all over again.

Final Thoughts

Seeing that foggy "Custom XML Data" warning is usually more confusing than it is concerning. This data is simply behind-the-scenes information that allows Excel to play nicely with other systems. Understanding what it does lets you make an informed decision about whether to keep it - to maintain important functionality - or remove it before sharing a file publicly.

Spending a few hours every Monday downloading CSVs, fixing weird data formatting issues, and just generally struggling to get different platforms to cooperate is a familiar pain. At the end of the day, your goal is to see your sales or marketing data, not become an expert on XML structures. This is exactly why we built Graphed. We connect directly to your data sources like Google Analytics, Shopify, and Salesforce, so you never have to deal with file exports and manual wrangling. You can just ask for the report you need in plain English and instantly get a live, automated dashboard, freeing you up to focus on insights, not file maintenance.