Someone sends you a .pptx deck and there's no PowerPoint on the computer in front of you. You don't need to buy anything. Which free option suits you depends on whether you only need to read the slides, or need to see them exactly as designed, or edit them.
Quick answer
- To read it with no account, open it in an online PPTX viewer that runs in your browser.
- To see the real design and animations, use PowerPoint for the web (free Microsoft account) or Google Slides (free Google account).
- To edit offline for free, use LibreOffice Impress on Windows, Mac or Linux, or Keynote on a Mac.
1. Open it in your browser with no upload
The SpeedyTools PPTX viewer opens the file inside your browser tab. Your browser reads the file on your device and never uploads it, which matters when the deck is confidential. You can step through the slides, search every slide for a word, zoom, go fullscreen, and copy or download all the slide text.
It is a lightweight preview. It shows each slide's text and pictures on a plain canvas, so themes, layout positions, charts, SmartArt and animations are not reproduced. Use it to read a deck quickly or to pull the text out of it. If you need to check how the slides look, use one of the options below.
2. PowerPoint for the web
Microsoft's browser version of PowerPoint is free with a Microsoft account. Upload the file to OneDrive, or drop it onto powerpoint.cloud.microsoft, and it opens with the original layout, fonts and most animations, and you can edit it. Microsoft keeps a copy of the file in your OneDrive.
3. Google Slides
Upload the .pptx to Google Drive and open it with Google Slides. Slides converts the deck. Most decks look right, but unusual fonts, some animations and complex charts can shift. Under File > Download you can save an edited copy back to .pptx.
4. LibreOffice Impress
LibreOffice is a free, open-source office suite. Its presentation app, Impress, opens and edits .pptx files offline. It also opens old .ppt files from PowerPoint 97-2003, and it suits anyone who can't use cloud services.
5. Keynote on a Mac, iPhone or iPad
Apple's Keynote is free on Apple devices and imports .pptx files. It warns you about any fonts or effects it had to substitute. Use File > Export To > PowerPoint to send a .pptx back.
What about old .ppt files?
The .ppt format from PowerPoint 97-2003 is an older binary format that many browser-based viewers can't read. LibreOffice, PowerPoint for the web and Google Slides all open it. To use a .pptx-only viewer, open the .ppt in one of those, save it as .pptx, then load the new file.
Which should you pick?
A browser viewer that reads the file on your device is the quickest and most private option, but it shows a simplified view. The cloud options show the real design and keep a copy of your file. The desktop apps show the real design without uploading anything, but you have to install them.