There isn't one Linux Office. There are two.

On Windows you get one Office, Microsoft's. On Linux you choose between two free programs. Both open Word, Excel and PowerPoint files, and both save back to Microsoft format. Same job, slightly different feel. Here is how to choose.

If you are not sure, start with LibreOffice. It is already installed, takes nothing extra, and 9 out of 10 people stay with it. If you spend all day in Microsoft 365 and miss the ribbon, install OnlyOffice too. You can keep both, opening each file with whichever you prefer.

The three apps inside LibreOffice: what each one does

Bonus apps you also get for free (do not worry about them on day one): Draw for diagrams, Base for simple databases (like Access), Math for typesetting equations.

Open a Word document from email: the five-minute walk-through

Your colleague sends a file called Q1-report.docx and you are on Linux. Here is the full round-trip, start to finish.

Make LibreOffice save as Word by default: turn off the "Use Word?" pop-up

By default, LibreOffice nags you every time you save a Word document. Easy fix: Tools → Options → Load/Save → General. Three "Always save as" rows at the bottom of the panel:

• Text document → set to Word 2007–365 (.docx)
• Spreadsheet → set to Excel 2007–365 (.xlsx)
• Presentation → set to PowerPoint 2007–365 (.pptx)

Click OK. From now on, Ctrl+S saves quietly in Microsoft format. No pop-up, no thinking. Your files round-trip exactly. (You can still pick .odt from Save As when you specifically want it.)

Spreadsheets: Calc opens Excel files with formulas and charts intact

LibreOffice Calc is the Excel replacement. Same grid of cells. Same column letters and row numbers. Same =SUM(A1:A10), =VLOOKUP, =IF, =COUNTIF, =AVERAGE. Calc speaks the exact same formula language as Excel. Open an .xlsx file and the formulas keep working, the charts keep drawing, the conditional formatting keeps highlighting.

One gotcha worth flagging: heavy Excel macros (the VBA scripting kind your accountant might use) sometimes do not translate cleanly. If your job depends on a complex .xlsm macro file, open it once on Linux to check it works before you commit. For 95% of spreadsheets (invoices, schedules, simple reports), no problem at all.

Slideshows: Impress opens PowerPoint files

LibreOffice Impress is the PowerPoint replacement. Open a .pptx, the slides look the same. Click Slide Show (or press F5), the presentation runs full-screen with your speaker notes on the second monitor. Same outline view on the left, same slide thumbnails. Save back to .pptx and your colleague gets exactly the deck you built.

Two small "but"s: some PowerPoint animations do not translate one-to-one (the simple fade-in / fly-in ones work; the elaborate "morph" transitions sometimes simplify). And a handful of Microsoft-only fonts (e.g. Calibri Light, Cambria) are not on Linux by default. See the font tip below.

Microsoft fonts: the one easy install that fixes most "looks different" complaints

If you open a Word document and the text reflows ever so slightly, it is almost always because Linux does not have the Microsoft font the doc was using (Calibri, Cambria, Arial, Times New Roman). Linux substitutes a similar free font, which is nearly the same width, but not quite, so a heading might wrap differently. The five-second fix:

Need the Microsoft 365 web apps? They work too.

If your company gives you a Microsoft 365 subscription, you can use the web versions of Word, Excel and PowerPoint on Linux. Go to office.com, sign in, click Word (or Excel or PowerPoint). Full-featured editing in the browser, same as on Windows. The only thing you cannot do in the browser is open files that are not already in your OneDrive (you would upload them first).

Tip: in Firefox or Chrome on Linux, right-click the tab and pick "Pin Tab". Word/Excel/PowerPoint live as pinned tabs the way they live as taskbar icons on Windows. Or "Install" the PWA (browser menu → "Install Office") to get a real dock icon.

PDFs: view, fill, sign, edit, combine

Almost every office document gets exported to PDF eventually: to send, to sign, to archive. On Linux, the everyday PDF actions are covered by a handful of small apps. Most are already installed.

Things that do NOT round-trip perfectly: the short, honest list

Being straight with you. For 95% of office work (letters, reports, school essays, invoices, simple spreadsheets, regular slide decks), no difference at all. The 5% that does not translate perfectly:

• Heavy VBA macros in .xlsm/.docm files. Some basic ones run; complex ones do not. If your accounting workflow depends on a 2,000-line Excel macro, test it on Linux before you switch, or keep one Windows machine just for that file.
• Fancy PowerPoint transitions (Morph, 3D, certain camera-zoom effects). Simple fades, wipes and fly-ins all work fine.
• Microsoft-only fonts not in the core-fonts pack. Most documents are fine after you install the fonts above. Some exotic corporate fonts may need to be manually copied across from your old Windows machine to ~/.fonts/.
• Co-authoring with a colleague in real time in .docx via the desktop apps. For real-time co-edit, use the web version of Word at office.com in your browser, or Google Docs.

The safe rule: if your job depends on a specific super-complex Office file, open a copy of it on Linux before you commit to the switch. For everyone else (students, regular office workers, freelancers), LibreOffice and OnlyOffice handle every document you are likely to send or receive.