Do viewers need an Apple ID to open a shared Keynote?
The two cases, in 60 words. An iCloud link needs an Apple Account only if you limited it to people you invited; with 'anyone with the link' it opens in a supported browser. A Linkdeck link never needs one: the deck plays in any browser on any phone or laptop, with no account and nothing to install.
The direct answer
It depends on how the deck was shared. Keynote's own sharing runs through iCloud and has two modes. Linkdeck hosts the HTML export on a normal web address, which takes Apple out of the viewer's side altogether.
iCloud: anyone with the link vs invited only
When you share from Keynote, you choose who can access the deck. Set to 'only people you invite', each viewer must sign in with an Apple Account that matches the invitation. Set to 'anyone with the link', no account is needed to view, but Apple's collaboration guide still lists what the viewer's device must run: Keynote on a recent iPhone, iPad or Mac, or Keynote for iCloud in a supported browser. On a Windows PC or an Android phone that means Keynote for iCloud in the browser, with whatever permission you set, and the viewer lands in an editor with a play button rather than on a presentation.
What 'supported browser' means for Windows or Android
Apple's requirements are written for people who will edit the deck, not for a client on a train. The link opens the working file, which means every edit you make shows up live and the viewer sees the editing interface first. It works, but it is not what most people mean by 'send them the deck'.
The no-account route: HTML export as a link
Export the deck (File → Export To → HTML…), zip the folder, upload it, and send the link. The viewer opens it like any web page. Keynote's own player runs in their browser with animations, builds, video and audio, and there is nothing to sign in to. The deck is a copy, so your working file is never exposed.
- iPhone and Android: opens in Safari or Chrome, landscape, tap to advance.
- Windows and Mac: opens in any current browser.
- Optional on Pro: a password, or an email address before viewing. Still no account.
Questions
Can an invited-only iCloud link be opened on Android?
Only by signing in to an Apple Account in the browser, with whatever permission you gave that person. If the viewer has no Apple Account, share with 'anyone with the link' instead, or send a hosted link that needs no sign-in at all.
Does Linkdeck ask viewers to sign up?
No. Viewers never create an account. If you turn on the email gate (Pro), they type an email address once and the deck plays; if you set a password, they type that. Otherwise the link just opens.
Can I still protect the deck without accounts?
Yes. On Pro you can add a password to the link, require an email before viewing, or both, and the viewer needs no account for either.
Upload and send a link that needs nothing
No Apple Account, no app, no download for the viewer. Free for the first deck.