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We answer: Why is a zipped Excel file not smaller?

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Updated onOctober 4, 2023

updated onOctober 4, 2023

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Some Excel users might need to reduce their spreadsheet file sizes so they can attach them to emails. Compressing an Excel file into a ZIP with the likes of WinZip might seem the most obvious way to do that. However, users who try zipping their Excel XLSX files are surprised to find that has little to no impact on the files’ sizes. In an MS supportforum post, one user stated:

I am trying to send some data to a colleague, whose email server has a 10 MB limit on attachments. The Excel file is 18 MB and was downloaded from an external source. I have tried removing any extraneous data, and zipping the file, but the size does not reduce.

File compression software, such as WinZip, has little impact on Excel XLSX files as they’re already compressed files. Thus, the XLSX format already utilizes ZIP compression. The format consists of zipped XML files that you can explore by changing the Excel file’s format to ZIP in File Explorer. Therefore, compression utilities can’t significantly compress the XLSX file much more.

So, users need to find alternative methods for either reducing Excel file sizes or sharing spreadsheets. One of the best ways to reduce an XLSX file is to save it as an XLSB instead. XLSB is the binary file format for Excel spreadsheets, which takes up less hard drive storage space.

How to save an Excel spreadsheet as an XLSB

How to share an Excel file via Google Drive

So, don’t waste your time trying to zip XLSX files. Instead, save them as XSLB files to reduce their size. If the file is far too big for email attachments, you’ll need to share the spreadsheet via cloud storage, such as Google Drive or OneDrive.

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Matthew Adams

Windows Hardware Expert

Matthew is a freelancer who has produced a variety of articles on various topics related to technology. His main focus is the Windows OS and all the things surrounding it.

He is passionate about the tech world, always staying up-to-date with the latest and greatest. With an analytical view, he likes problem-solving, focusing on errors and their causes.

In his free time, he likes to read and write about history and tries to always develop new skills.

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Matthew Adams

Windows Hardware Expert

He is passionate about everything surrounding Microsoft’s OS, focusing on troubleshooting guides & tips for everyday problems.