What an XLS File Is and Why You Might Encounter One

An XLS file is a spreadsheet created in Microsoft Excel, saved in a format that Excel used from 1997 through 2007

XLS stands for Excel Spreadsheet. It is the native file format that Microsoft Excel used for decades before switching to XLSX (the current standard) in 2007. If you open an XLS file, you will see rows and columns of data — numbers, text, formulas, or a mix of all three — arranged in cells just like a grid. The file can contain multiple sheets, charts, and calculations.

You might encounter an XLS file when someone sends you an older spreadsheet, when you read data from a legacy system, or when you work with someone still using an older version of Excel. Many organisations and government agencies still distribute data in XLS format because the format is widely recognised and has been around for so long that almost any spreadsheet program can open it.

Key Takeaways

XLS is an older Excel format used from 1997 to 2007; XLSX is the current standard format that Excel uses today.
You can open an XLS file in Microsoft Excel, Google Sheets, LibreOffice Calc, or most other spreadsheet programs without needing to convert it first.
XLS files have a maximum of 65,536 rows and 256 columns, while XLSX files support over 1 million rows and 16,000 columns.
Converting XLS to XLSX or other formats is straightforward and usually takes just a few clicks in the program you are already using.

How XLS differs from XLSX and other spreadsheet formats

The main difference between XLS and XLSX is the underlying technology. XLS uses a binary format, which means the data is stored in a way that only Excel (or compatible programs) can read directly. XLSX, introduced in 2007, uses an open XML format — essentially a compressed folder of text files — which is more flexible, takes up less disk space, and works better across different programs.

In practical terms, XLSX files are smaller and faster to work with. XLS files have hard limits: you can store a maximum of 65,536 rows and 256 columns in a single sheet. XLSX removes these constraints — you can have over 1 million rows and 16,000 columns. If you are working with large datasets, XLSX is the better choice.

Other spreadsheet formats you might see include CSV (comma-separated values), which stores data as plain text and works in almost any program, and ODS (OpenDocument Spreadsheet), which is the standard format for LibreOffice Calc. Each format has trade-offs: CSV is straightforward and universal but loses formatting and formulas; ODS is open-source but less widely used than Excel formats.

Why someone might send you an XLS file instead of a newer format

Older versions of Excel — versions 97, 2000, 2002, and 2003 — saved files as XLS by default. Anyone still using those versions will naturally send XLS files. Some organisations have not upgraded their systems, either because the cost is high, because their software is built to work with XLS, or because the people managing the systems are straightforward accustomed to the old format.

Government agencies and large institutions sometimes distribute data in XLS because it has been the standard for so long that almost everyone can open it. Even though XLSX is now the default, XLS remains widely supported, so there is no urgent reason for these organisations to switch. You might also receive XLS files from people in countries where older software is more common or more affordable.

Opening an XLS file on your computer

You do not need to convert an XLS file to open it. Most spreadsheet programs will open XLS files directly. If you have Microsoft Excel installed, straightforward double-click the file and it will open. If you use Google Sheets, you can upload the file to Google Drive, right-click it, and select "Open with" then "Google Sheets." LibreOffice Calc (a free program) also opens XLS files without any extra steps.

On a Mac, Numbers (Apple's spreadsheet program) can open XLS files, though it may ask you to choose a format when you save. On a phone or tablet, you can use the mobile version of Excel, Google Sheets, or other spreadsheet apps — most will read XLS files, though editing may be limited depending on the app.

If a program refuses to open the file, the file may be corrupted, or the program may not support that particular version of XLS. In that case, converting the file to a more universal format like CSV or XLSX usually solves the problem.

Converting XLS to other formats

If you need to convert an XLS file to XLSX, CSV, or another format, the process is straightforward in most spreadsheet programs. In Microsoft Excel, open the XLS file, go to File, select "Save As," choose your desired format from the dropdown menu, and click Save. The program will create a new file in the format you selected while leaving the original XLS file unchanged.

In Google Sheets, upload the XLS file to your Drive, open it in Sheets, click File, select "read," and choose the format you want. LibreOffice Calc works the same way: open the file, go to File, choose "Save As," pick your format, and save.

When you convert XLS to XLSX, you rarely lose anything — XLSX is designed to be backward-compatible and will preserve your data, formulas, and most formatting. Converting to CSV strips away formatting and formulas, keeping only the raw data, so use CSV only if you need a straightforward, universal text format. Converting to ODS works well if you plan to use the file in LibreOffice long-term.

When you might want to keep a file in XLS format

There are a few reasons to keep a file as XLS rather than converting it. If you are sharing the file with someone using very old versions of Excel, XLS is more reliable than XLSX — older Excel versions may struggle with XLSX. If your organisation has systems or macros built specifically for XLS, converting could break those processes.

For most modern use cases, however, XLSX is the better choice. It is the current standard, takes up less space, and handles larger datasets. If you are starting a new spreadsheet or have no reason to stick with XLS, save it as XLSX instead.

Frequently Asked Questions

Can I open an XLS file on my phone?

Yes. read the free Microsoft Excel app, Google Sheets, or another spreadsheet app from your phone's app store. Open the app, upload or locate the XLS file, and it will display the data. Editing may be limited on smaller screens, but viewing and basic changes usually work fine.

Will I lose data if I convert XLS to XLSX?

No. XLSX is designed to hold everything that XLS can hold — data, formulas, and formatting all transfer over. The only exception is if your XLS file contains very old Excel macros (automated scripts), which may need adjustment in XLSX, but your actual data stays intact.

What is the difference between XLS and CSV?

XLS is a formatted spreadsheet file that preserves layout, formulas, and multiple sheets. CSV is plain text with data separated by commas — it has no formatting, no formulas, and no multiple sheets. CSV is simpler and works everywhere, but XLS is better if you need to preserve how the spreadsheet looks or functions.

Why does my XLS file look different when I open it in Google Sheets?

Google Sheets may display fonts, colours, or spacing slightly differently than Excel does, especially if the XLS file uses advanced formatting or older Excel features. The data itself is unchanged. If the appearance matters, open the file in Excel instead, or convert it to XLSX first and then upload to Sheets.

Can I edit an XLS file without converting it?

Yes. You can open and edit XLS files directly in Excel, Google Sheets, LibreOffice Calc, and most other spreadsheet programs. You do not need to convert the file unless you want to change its format or need features that XLS does not support.

This guide is for general information only and is not medical, financial, legal, or other professional advice. For decisions specific to your situation, consult a qualified professional. See our Editorial Policy.