Microsoft Office Formats: What They Are and When to Use Each One

If you work with Word, Excel or PowerPoint, sooner or later you will come across dozens of extensions and options to save and share your files. Choose the format well It is not just a technical issue: it affects the size of the document, its compatibility, the possibility of editing it and even security (macros).

In this guide we gather, in one place, all file formats that Microsoft Office y Microsoft 365 can open, save or export, what they are for, when it is convenient to use each one and what you should take into account when sharing with old versions, with other suites (such as Opendocument) or when working on the web version versus the desktop.

Open XML and modern extensions: the foundation of everything

For years, Word, Excel and PowerPoint have saved by default in formats OpenXML (docx, xlsx, pptx). These files are internally ZIP packages containing XML and resources, which provides key advantages: smaller size (compression greatly reduces weight), better recovery if a component is damaged, privacy (it's easy to detect and remove metadata with the Document Inspector), and interoperability (anyone with an XML editor and a ZIP utility can inspect them).

An important thing in Open XML is the distinction between files with and without macros. Extensions with “x” (docx, xlsx, pptx) cannot contain macros and those ending in “m” (docm, xlsm, pptm) ​​do allow them. This makes it much easier to recognize at a glance whether a file can execute code.

In addition to the documents, there are variants for templates and add-ins: Word uses dotx and dotm, Excel uses xltx and xltm, and PowerPoint uses potx and potm; the accessories Modern Excel formats are called xlam and PowerPoint formats are called ppam. There is also the Open XML Strict Spreadsheet (xlsx “strict”), a stricter ISO variant for Excel workbooks.

Extensions per application: what each program creates

Word works primarily with . Docx (document without macros) and .doc (document with macros). For templates, use .dotx y .dotmThese extensions are the ones that ensure the best compatibility with modern features (such as AutoSave and accessibility checks) (see Word formats explained).

Excel uses . Xlsx (book without macros), .xlsm (book with macros), .xltx y .xltm (templates). There is also .xlsb, a binary book designed for faster loading and saving and to handle large volumes of data with agility; it supports VBA and new features, but it is not XML and does not lend itself to manipulating its contents outside of Excel with the same ease (see Excel formats).

PowerPoint saves to . Pptx (presentation without macros) and .pptm (with macros). For templates, there are .potx y .potm; for “loose slides” there are .sldx y .sldm; for ready-to-play presentations, .ppsx y .ppsm. In addition, the suite includes the Office theme (.thmx) that applies styles consistently across documents, spreadsheets, and presentations (see PowerPoint formats).

When to use each Office format (docx/xlsx/pptx, variants with macros and templates)

For general text documents, it is normal to . Docx. It guarantees compatibility, a small size, and all the modern features. .doc only when you really need macros (VBA or XLM) and for security, it is ideal to sign macros and share only with those you trust.

In Excel, the standard is . Xlsx. If your book includes macros o macro sheets from Excel 4.0, choose .xlsm. When performance is key (very large workbooks, many calculations or pivot tables), .xlsb can make a difference in opening and saving, while maintaining compatibility with VBA.

For templates that you are going to reuse (budgets, reports, sheets), use .dotx / .dotm, .xltx / .xltm y .potx / .potm. Avoid using templates with macros If they are not essential: this is how you reduce security notices and possible blockages in corporate environments.

Export for sharing or printing: PDF and XPS

When the goal is preserve the design and avoid changes, choose PDF (.pdf). It is perfect for sending proposals, manuals or documents to be printed (including commercial printing). The format keeps the elements as you designed them and is not easily edited.

There is also XPS (.xps), a paper XML specification with a similar purpose: respect the format and complicates editing. It is less common than PDF, but some organizations use it due to internal policies or Windows.

Publish to the web: HTML and MHT/MHTML

If you need to publish a spreadsheet or document as a web, you can export to HTML (.htm, .html). Office generates a folder with the file and all the resources (images, scripts). For a single file that encapsulates everything, it is MHT/MHTML, “single-file web page”, useful for emailing or archiving with embedded resources.

Interoperability with other suites: ODF (OpenDocument)

Office opens and saves in Opendocument for spreadsheets with .ods (there are also .odt and .odp in other apps, although we focus on Excel here). It is useful if you collaborate with users of Google Docs or OpenOffice/LibreOffice, since they will be able to open it natively.

However, since the features are not identical between suites, save and reopen in ODF You may notice changes or loss of formatting. Practical recommendation: work in xlsx/docx/pptx while creating and reviewing, and export to ODF as the final exchange format only if specifically requested.

Data formats and exchange in Excel: CSV, TXT, DIF, and SYLK

Excel shines when it acts as a data bridge. To exchange data with other systems, you have several text and legacy formats, each with its own "when to use it." Choosing the right one It saves you problems with accents, line breaks or separators.

• CSV (.csv): text file with comma separated values. There are platform variants (Windows, Macintosh, MS-DOS) that aim to make tabs, line breaks and other characters interpret well on that system. Excel saves only the active sheet.
• Tab-delimited text (.txt): the fields are separated with tabulators. Also with Windows/Mac/MS-DOS variants, and option unicode text (for wide character encoding). As CSV, save the current sheet.
• DIF (.dif): classic format of data exchange. Saves only the active sheet; it's used less today, but still appears in legacy integrations.
• SYLK (.slk): Format symbolic link for exchange between legacy applications; retains some tabular metadata. Also active sheet only.
• PRN (.prn): “Formatted text (space delimited)”. Intended for outputs such as Lotus and space-aligned printed lists; saves only the active sheet.

Practical advice: if you are going to import into a system that only “swallows” a specific delimiter, choose CSV (comma) or TXT (tab) as requested. If there is a risk with accents or special characters, bet on unicode text. For legacy automations, DIF/SYLK is still useful.

Special and legacy formats in Excel

Excel can open but not save in certain older or third-party formats. For example, .dbf (dBase III/IV) opens, but you can't save to dBase from modern Excel. There is also opening support for .xlw (Excel 4.0 workbook), although you will not be able to save with that extension.

In the category “open but with nuances” is .xlr (Microsoft Works 6.0–9.0). To work with these files, it is advisable to convert them to .xlsx/.xlsm/.xlsb and review compatibility before using them in production.

Formats not supported in Excel (modern versions)

There are formats that can no longer be opened or saved in Excel 2007/2010/2013/2016 and later. Avoid depending on them and migrate as soon as possible.

• Excel chart (.xlc) from Excel 2.0/3.0/2.x.
• lotus 1-2-3 in all its variants: .wk1, .wk2, .wk3, .wk4, .wks, .fmt, .fm3.
• Microsoft Works (.wks).
• DBASE II (.dbf) in its specification 2.
• Quattro Pro for MS-DOS and Windows: .wq1, .wb1, .wb3.

If you need to recover data from one of these formats, the most sensible thing to do is convert with an intermediate tool (a specific converter or by opening it first in an application that still supports it and re-exporting to CSV, XLSX or similar).

Plugins and Automation: XLA and XLAM

Excel supports legacy add-ins .xla (Excel 97–2003) and modern ones .xlam, which are also macro-enabled and XML-based. If you develop in-house solutions, See how to troubleshoot plugins and strives to offer both 64-bit and 32-bit versions whenever possible to cover both environments.

XML, data and previous standards

Beyond Open XML, Excel can work with XML data (.xml) and with the XML Spreadsheet 2003. These formats are interesting if you are going to exchange information with other apps that process XML or if you need custom schemas. Note that the modern standard for books is .xlsx/.xlsm, more compact and robust.

Clipboard: Formats that Excel understands when pasting

When you copy and paste, Excel can receive data in multiple formats from the Clipboard from Office (if you can't paste external content, see you cannot paste external content). This includes WMF/EMF images, BMP bitmaps, formats of text (tab, CSV, rich text RTF), OLE objects, and even single-file web pages MHT/MHTML or traditional HTML. This makes pasting from other applications much more conserves content and formatting.

Backward compatibility and checker

Opening old documents in Office is straightforward: they open and you can continue working with them. When you save back, Office runs a compatibility checker which warns you of features not supported by the target version and allows you to remove or replace them. If the collaboration is mixed by versions, the most practical option is save in modern format and facilitate, if necessary, additional export.

Do you still have documents in the old binary formats (.doc, .xls, .ppt)? Open the file and choose File> Save As (or “Save a copy” if you are on OneDrive/SharePoint) to create the version OpenXMLYou'll gain in size, reliability, and features.

When to choose 64-bit or 32-bit Office/Microsoft 365

64-bit editions of Office make better use of memory and are ideal if you work with huge files or complex models in Excel (multiple pivot tables, external connections, Power Pivot, 3D Map, Power View or Get & Transform). They also help in PowerPoint with very large images and videos and in Project with files >2 GB.

The 32-bit version is still recommended if you depend on COM add-ins or 32-bit controls without a 64-bit alternative, if you VBA code use old API declarations that are difficult to port, or if you deal with OLE objects/servers and databases .mde/.ade/.accde 32-bit Access. Additionally, computers with less than 4 GB or 32-bit systems can only install the 32-bit edition.

OpenDocument vs. Open XML: Which is better by default?

OpenDocument was designed for suites like OpenOffice/LibreOffice, while Open XML is native to Microsoft Office. Office supports ODF and you will be able to open/save, but if you use non-equivalent functions there may be losses or changes in presentation or behavior. Therefore, unless your organization requires it, it is most sensible to work in docx/xlsx/pptx and export to ODF only for one-off exchange.

Office desktop vs. web version: differences that influence the format

Microsoft 365 on the web is free and convenient, but it has limits. Word web tools such as complete management are missing citations and bibliography, watermarks, advanced design and printing options, or the "pro" collaboration option of combining and comparing documents. Still, it handles basic editing and simple co-authoring very well.

En Excel web You can create and edit pivot tables, but not pivot charts (only view them), there are no advanced formulas no external connections or external references, and lacks analytical views such as Power View, Power Pivot, or complex slicers such as TimelineFor serious analysis and data modeling, the desktop wins hands down.

En PowerPoint web the selection of transitions and animations It is smaller, it does not reproduce certain embedded videos, rich formatting of shapes and text is limited (no gradients or eyedroppers), and there are no Designer nor the ink stand. For complex presentations, a desktop is suitable.

In addition, the web version doesn't work offline and, to edit a local file, you must upload it to OneDrive first. All of this doesn't change the format you “must” use, but it does explain why for documents with macros, large Excel templates or elaborate designs, the desktop and .xlsm/.xlsb/.pptm/.dotm formats are still king.

Legacy Binary Formats: When They Still Make Sense

The formats .doc, .xls, .ppt (97–2003) are maintained for compatibility, but are no longer recommended as a standard. You lose the benefits of Open XML and expose yourself to more problems when recovering damaged files or collaborating. Use these formats only if an application antigua demands it, and plans its migration.

Quick tips for choosing a format

• Modern, editable document: docx/xlsx/pptx.
• Macros necessary: ​​docm/xlsm/pptm (digital signature if possible).
• Performance on large books: xlsb.
• reusable templates: dotx/xltx/potx (or “m” variants if they have macros).
• Share without editing: PDF (or XPS under Windows policies).
• Publish as web: HTML or MHT/MHTML (single file).
• Exchange data with systems: CSV/TXT (Unicode if there are accents), DIF/SYLK if requested.
• Mixed work with other suites: Keep your work in Open XML and export to ODF at the end.

Choosing the right format not only avoids compatibility issues; saves you time, reduce errors in integrations, and improve the experience of those who receive your files. With these guidelines, you can make informed decisions in each case.