Is there an online Keynote viewer?

Yes, two, and which one you want depends on which side of the email you are on. If you received a .key file, Keynote for iCloud opens it in a browser on a Windows PC or a Mac once you sign in with a free Apple Account. If you are the one sending, export the deck to HTML and host it, so the viewer needs no account, no app and no Apple device.

If someone sent you a .key file

Keynote itself runs only on Apple devices. On anything else, the browser route is:

  • Go to icloud.com and sign in, or create a free Apple Account with any email address.
  • Open Keynote, upload the .key file, and press Play.
  • Expect differences: fonts the sender used may be substituted, and Apple Community users report that some transitions and builds play differently, or not at all, in the browser.
  • On a phone this is awkward. Ask the sender for a link or a PDF instead.

If you are sending the deck

Do not make the viewer do the steps above. Export the presentation (File → Export To → HTML… in Keynote for Mac), drop the folder on linkdeck.me, and send the link. Apple's own player runs in the viewer's browser, with builds, transitions, video and audio, and there is nothing to sign in to or install.

Other 'Keynote viewers' you will find

Search results also offer online converters that turn a .key into a PDF or a PowerPoint file. They flatten builds and video, and you upload your file to a site you know little about. For a client deck, that is two good reasons to use one of the routes above.

Which to use

SituationUse
You received a .key and have a computerKeynote for iCloud in the browser
You received a .key on a phoneAsk the sender for a link or a PDF
You are sending a deck to people without KeynoteHTML export as a hosted link
You need others to edit the deckKeynote collaboration via iCloud

Questions

Is Keynote for iCloud free?

Yes, with a free Apple Account. Files you upload count toward your iCloud storage, and the free tier is 5 GB.

Can I open a .key file on Windows without iCloud?

Not with its animations intact. Keynote only runs on Apple devices; outside iCloud, the options are converters or asking the sender for another format.

Does a Linkdeck link need an Apple Account?

No. It opens like any web page on iPhone, Android, Windows or Mac. Viewers never create an account.

Sending a Keynote? Send a link that needs nothing

Export to HTML, drop the folder, send the link. The first deck is free.

Upload a Keynote export

Free for 3 days. €9 once keeps one deck for good; €12 a month keeps every deck. See pricing