Compare XLSX vs. ODS vs. FODS: The Ultimate Open Format Showdown

Last Updated: 01 Dec, 2025

In the world of spreadsheets, most of us just click “Save” without a second thought. But behind that simple action lies a critical choice: which file format should you use? While the default might be Microsoft Excel’s XLSX, a new era of open-source software has brought powerful alternatives like ODS and FODS into the spotlight.

Choosing the right format isn’t just about compatibility; it’s about data integrity, future-proofing, and accessing advanced features. So, let’s dive deep into the ultimate open format showdown: XLSX vs. ODS vs. FODS.

First, What Makes a Format “Open”?

Before we compare, let’s define our terms. An open file format is one that is:

• Publicly Available: Its specifications are documented and accessible to anyone.
• Royalty-Free: Developers can implement it in their software without paying licensing fees.
• Standardized: Often maintained by a neutral standards organization (like OASIS or ISO).

Why does this matter? Open formats prevent “vendor lock-in,” ensuring your data remains accessible for decades, regardless of which software company rises or falls. They are the cornerstone of digital preservation and software interoperability.

Understanding the Contenders

Before we pit these formats against each other, let’s get acquainted with each one.

XLSX is Microsoft’s Excel format that debuted with Office 2007. It replaced the older XLS format and quickly became the de facto standard for spreadsheets worldwide. Built on Office Open XML, XLSX files are essentially compressed packages containing XML files that define your spreadsheet’s structure, data, and formatting.

ODS stands for OpenDocument Spreadsheet, part of the OpenDocument Format (ODF) family. Developed as an open standard by OASIS, ODS was designed to be vendor-neutral and fully transparent. It’s the native format for LibreOffice Calc and Apache OpenOffice, and it’s gained traction among organizations that prioritize open standards.

FODS is the flat XML version of ODS. While ODS files are compressed archives (similar to XLSX), FODS stores everything in a single, uncompressed XML file. This makes FODS the outlier of our trio, but one with some surprisingly practical advantages.

Contestant #1: XLSX - The Industry Titan

What it is: The default format for Microsoft Excel (2007 and later).

The Tech Under the Hood: XLSX is part of the Office Open XML (OOXML) family. It’s essentially a ZIP archive containing a collection of XML files for your data, styles, formulas, and settings. This makes it more efficient and less prone to corruption than its predecessor, the binary XLS format.

Pros of XLSX:

• Ubiquitous Compatibility: As the Excel standard, it’s supported by nearly every modern spreadsheet application, including Google Sheets, LibreOffice Calc, and Apple Numbers. It’s the lingua franca of the business world.
• Feature-Rich: Supports the vast array of advanced Excel features, including Power Pivot data models, sophisticated charts, slicers, and complex conditional formatting.
• Familiarity: It’s the format everyone knows and expects. Sharing an XLSX file rarely raises questions.

Cons of XLSX:

• Proprietary Roots: While now an ECMA and ISO-standardized open format, it was originally created by Microsoft and is still heavily influenced by them. Purists argue it’s not as “open” as its competitors.
• Potential for Compatibility Glitches: When opening a complex XLSX file in other suites (like LibreOffice), there’s a small chance some advanced formatting or macros may not translate perfectly.

Best For: Anyone working primarily in a Microsoft Excel environment, sharing files with a wide range of users in a business setting, or using advanced, Excel-specific features.

Contestant #2: ODS - The Open Source Champion

What it is: The default format for LibreOffice Calc and Apache OpenOffice Calc.

The Tech Under the Hood: ODS stands for OpenDocument Spreadsheet. It’s an ISO/IEC standard (26300) and uses a similar ZIP/XML structure as XLSX. It was designed from the ground up to be a truly open and vendor-neutral standard.

Pros of ODS:

• Truly Open Standard: As an ISO standard, it is completely vendor-neutral, ensuring long-term access to your data without relying on a single company.
• Excellent Open-Source Integration: It’s the native format for LibreOffice and OpenOffice, offering flawless performance and feature support within these suites.
• Strong Compatibility: Modern versions of Microsoft Excel (since 2010) have solid support for opening and saving ODS files, though minor formatting issues can occasionally occur.

Cons of ODS:

• Not Perfect in Excel: While it works in Excel, some advanced ODS features (or specific formula implementations) may be lost or altered when saved by Microsoft’s software.
• Less Common in Business: You’re less likely to receive an ODS file from a corporate partner, which can cause momentary confusion.

Best For: Users of LibreOffice or OpenOffice, open-source advocates, governments and public institutions mandating open standards, and anyone prioritizing long-term data preservation.

Contestant #3: FODS - The Simple, Transparent Underdog

What it is: A Flat XML ODF Spreadsheet.

The Tech Under the Hood: This is the key differentiator. Unlike XLSX and ODS, which are ZIP packages, a FODS file is a single, uncompressed XML file. If you open it with a text editor, you can read all your spreadsheet data and formatting in a structured, human-readable form.

Pros of FODS:

• Human-Readable & Transparent: The biggest advantage. You can inspect, and even manually edit, the entire spreadsheet structure with a basic text editor. This is a dream for developers and data auditors.
• Excellent for Version Control (Git): Because it’s a single text file, version control systems like Git can effectively track changes line-by-line. You can see exactly which cell was modified, unlike with the binary-like ZIP packages where the entire file is seen as changed.
• No Compression Overhead: Simplifies reading and writing for software, as there’s no need to pack or unpack a ZIP archive.

Cons of FODS:

• Large File Size: Without compression, a FODS file can be significantly larger than its ODS or XLSX equivalent for the same data.
• Limited Software Support: This is its major drawback. While LibreOffice Calc handles it natively, Microsoft Excel cannot open FODS files. This severely limits its practicality for general sharing.

Best For: Developers, data scientists using version control, and situations where data transparency and the ability to script edits to the XML are more important than universal compatibility.

Head-to-Head Comparison Table

The Verdict: Which Format Should You Choose?

The “best” format isn’t a one-size-fits-all answer; it depends entirely on your workflow.

1. Choose XLSX if: You live in Microsoft Excel, need to guarantee flawless compatibility with colleagues and clients, and rely on advanced Excel-specific tools. It’s the safe, practical choice for the corporate world.
2. Choose ODS if: You primarily use LibreOffice or OpenOffice, believe in supporting truly open standards, work in an environment that mandates them (like many government agencies), and want the best balance of openness and compatibility.
3. Choose FODS if: You are a developer, you use Git for tracking spreadsheet changes, or you have a specific need to parse or generate spreadsheet data using XML tools. Its use case is more niche but incredibly powerful within that niche.

Pro-Tip for Maximum Compatibility

When in doubt, the safest format for sharing with a unknown or mixed audience is still XLSX. However, if you are an open-source user sharing with an Excel user, a good practice is to share your file in ODS, but also provide a static PDF export for a guaranteed consistent visual layout.

The Bottom Line

The competition between XLSX, ODS, and FODS is a positive sign of a healthy, competitive software ecosystem. XLSX wins on ubiquity, ODS wins on philosophical openness and integration, and FODS wins on technical transparency. By understanding their strengths and weaknesses, you can make an informed choice that protects your data and supercharges your workflow.

FAQ

Q1: Which format is best for sharing spreadsheets with Microsoft Excel users?

A: XLSX is the best choice for maximum compatibility with Microsoft Excel users.

Q2: Can Microsoft Excel open and edit FODS files?

A: No, Microsoft Excel cannot open FODS files, making it a poor choice for Excel-centric workflows.

Q3: Why would I use ODS instead of XLSX?

A: Use ODS if you prioritize a truly vendor-neutral open standard or work primarily in LibreOffice/OpenOffice.

Q4: What is the main advantage of the FODS format?

A: The main advantage of FODS is that it’s a single, human-readable XML file, ideal for version control systems like Git.

Q5: Is the XLSX format considered an open standard?

A: Yes, XLSX is an ECMA/ISO-standardized open format, though it was originally developed by Microsoft.

See Also

• What is Excel? Key Information You Need to Know
• Excel File Formats: XLSX, XLSM, XLS, XLTX, XLTM
• Difference Between XLS and XLSX