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Philleywood
User level: Level 1 (6 points)

Keynote 15.4 shows horizontal rendering glitch on displays

Keynote 15.4: Horizontal Rendering Glitch Appears on Both MBP and External Displays


Since updating to Keynote 15.4 (auto update yesterday, 9/30/26), I intermittently get a large horizontal rendering band when toggling into/out-of Edit Slide Layouts. The artifact issue appears whether I'm using my MacBook Pro display or a connected external monitor, so it does not appear to be specific to the display.


Artifact stays onscreen unless I do one of the following:

• Jiggle the Keynote window

• Move the Keynote window from one display to the other

• Make the Keynote window smaller then resize it again

• Go into Play mode, then out again


All of these force a redraw and make the band disappear. Restarting Keynote or the Mac does not prevent it from happening again.


A fresh presentation using one of Apple's dynamic themes does not reproduce the issue, but it does reproduce every time across a series of presentations I've been building in a 5:1 widescreen format which produced no issues until yesterday's update. These decks have video backgrounds in the masters, but the issue also happens on slides where there are still-image backgrounds or a simple color fill.


System:

Keynote 15.4 (7051.0.79)

MacBook Pro 16-inch, 2023, M2, 16 GB memory

macOS Tahoe 26.6.2



[Edited by Moderator]

Posted on Oct 1, 2026 12:46 PM

3 replies

Richard.Taylor
User level: Level 7 (25,466 points)

Oct 2, 2026 8:10 AM in response to Philleywood

As a troubleshooting step, try restarting in Safe Mode.This bypasses certain potentially disruptive processes, and it often helps. Safe Mode is different for different computers, so see this: 

           Start up your Mac in safe mode - Apple Support 


It says that, for a Silicon Mac, you shut down and then

  1. Press and hold the power button on your Mac until “Loading startup options” appears.
  2. Select a volume.
  3. Press and hold the Shift key, then click Continue in Safe Mode.


Philleywood Author
User level: Level 1 (6 points)

Oct 23, 2026 12:51 PM in response to drc_norman

Unfortunately, no. And I've been in the middle of a very busy project so I have just been working around it, which is frustrating. I did not attempt the Safe Mode solution mentioned above because I cannot do my Keynote work that way. I hope someone can solve the problem, because it persists with the 4:1 and 5:1 widescreen formats I've been working in.

drc_norman
User level: Level 1 (8 points)

Oct 23, 2026 12:27 PM in response to Philleywood

I just started having the same issue. Were you able to find any solutions?




Originally posted at discussions.apple.com/thread/256368682