The Keynote file (.key)

A .key file is most often a presentation from Keynote, Apple's presentation app. Apple unveiled Keynote at Macworld Expo on 7 January 2003, as a $99 app that could import and export PowerPoint files. Today it's free on every Mac, iPhone and iPad, runs on Apple Vision Pro, and works in a browser as Keynote for iCloud. Since early 2026, an optional Apple Creator Studio subscription adds premium templates and AI features.

A Keynote presentation holds slides built from master slides and a theme, with text, shapes, images, charts, tables, audio and video, animations (Keynote calls them builds), transitions, presenter notes and comments. In 2013 Keynote 6.0 moved to the storage format shared with Pages and Numbers, and current versions still use it.

Three things a Keynote file is not:

• Not a PowerPoint file. PowerPoint, Google Slides and most other programs can't open .key files. To share with them, export to PPTX or PDF.
• Not an open format. Apple publishes no specification for current files; what's known about the inside comes from reverse engineering.
• Not the only kind of .key file. Private keys for web servers and SSH, and licence keys for software, use the same extension. They're plain text and have nothing to do with Keynote.

The extension doesn't tell you, but the first bytes do. Open a copy in a plain-text editor (Notepad, TextEdit in plain-text mode, or head -c 64 file.key in a terminal): a Keynote file starts with PK and then binary data, a key file with readable text.

On a Mac, .key is linked to Keynote, so double-clicking a private key file launches Keynote, which can't open it. Nothing is wrong with the key: open it with the program that needs it, or a text editor.

Since 2013, Keynote presentations are made of IWA (iWork Archive) files, shared with Pages and Numbers. The structure has been worked out by the SheetJS project, the authors of keynote-parser and other reverse engineers:

• Each .iwa file is Snappy-compressed in chunks: a 00 byte, a 3-byte length, then Snappy data.
• Inside are Protocol Buffers messages. The message definitions are compiled into the apps; reverse engineers extract them from the app binaries. Some are used only by Keynote, others by all three apps. They change between Keynote versions, which is why tools like keynote-parser need updating for each new release.
• Objects point to each other by number. Index/Metadata.iwa maps the document's components to the files that hold them.
• Media stays as it is. Pictures, audio and video sit in the Data folder of the ZIP as ordinary files.

According to Apple, current iWork apps open documents made with any version of iWork. Keynote saves a single file by default. On a Mac you can switch to a package, or back, with File, Advanced, Change File Type. Keynote may suggest a package for presentations over 500 MB on disks that don't use APFS.

Keynote is a good format while everyone involved uses Apple devices. When someone on Windows or Android needs to edit the deck, send a PPTX; when they only need to read or present it, a PDF or a movie looks the same everywhere.

1. 1Use Keynote for iCloud. Go to iCloud.com in a browser on Windows or any computer, sign in with an Apple Account (creating one is free), open Keynote and upload the file. You can view, edit and play the presentation there, then download a copy as Keynote, PDF or PowerPoint.
2. 2Ask the sender to export it. In Keynote: File, Export To, PowerPoint (or PDF). This is the most reliable route, because the person exporting can check the result.
3. 3Look at the preview, as a last resort. Rename a copy to .zip, open it, and open preview.jpg. It's only a thumbnail, not the slides. Pictures and videos from the slides are in the Data folder.

• Passwords carry over: exporting a password-protected presentation to PDF, PowerPoint or Keynote '09 keeps the password unless you change or remove it in the export dialog.
• From PowerPoint to Keynote: Keynote opens PPTX files on Mac, iPhone, iPad and iCloud.com. It may warn about missing fonts or changed appearance.
• Check the result in PowerPoint. Keynote and PowerPoint lay out text with different engines and fonts, and some effects have no equivalent. Open the exported PPTX before sending it, and play the builds and transitions.

• PowerPoint or Google Slides can't open it. Neither reads .key files. Convert it through Keynote or iCloud.com first.
• The attachment arrived as a folder, a ZIP or a broken file. The presentation was saved as a package. Ask the sender to choose File, Advanced, Change File Type, Single File, and send it again.
• Windows shows an unknown file type, or opens it in the wrong program. Windows has no program for Keynote. Check the first bytes: if it's text starting with -----BEGIN, it's a private key, not a presentation.
• Keynote says it can't open the file. It may not be a presentation at all, but a key or licence file. Apple also says a dimmed file in the open dialog isn't in a format Keynote can open.
• Fonts look different. Keynote warns about missing fonts when a presentation uses fonts your device doesn't have. Install the fonts, replace them, or ask for a PDF.
• The file is huge. Almost always video and full-size photos in the Data folder. Export a movie or PDF for viewers, or replace large media before sending.

Keynote has no macro language inside documents, so a .key presentation can't carry VBA-style macros the way a .pptm can. A few things are still worth knowing:

• Presenter notes, comments and skipped slides travel with the file. Remove them, or send a PDF exported without them, before sharing outside your organisation.
• Preview images show content. The thumbnails inside an unencrypted presentation are pictures of it. Anyone who unzips the file can see them.
• Password hints are not secret. iWork keeps the hint unencrypted; in our password-protected Numbers sample it sits in plain text in its own entry of the ZIP. Never put the password in the hint.
• Links on slides can point anywhere. Check where they go before clicking.
• Parsing uploads on a server. A Keynote file is a ZIP of compressed binary data, so a server that reads uploaded files inherits ZIP risks such as archive bombs. Limit file size and decompressed size.
• A .key that is a private key is a secret, not a document. See "Is it a Keynote file or a key?" above: never upload or publish it.