Your camcorder clip or an old movie file plays in Windows 11, but there is no sound. Sometimes a message says the audio format cannot be played. The picture is fine.
The missing piece is AC-3, the Dolby Digital sound in many videos, and Windows 11 stopped shipping it. I would switch players before you hunt for a codec download. Microsoft offers none.
A second fault arrived on 22 September. On PCs that still have AC-3, some apps now close when they play it, and Microsoft confirmed that on 2 October.
Why the sound went missing
Microsoft's media player troubleshooting page puts it plainly: "Beginning with Windows 11, version 24H2, the AC-3 codec is no longer included with Windows."
It adds that "many device manufacturers will pre-install an AC-3 codec", and that a PC upgraded from an earlier version keeps it. So if your PC is new or freshly installed, it is the one likely to be silent.
One owner found exactly that split. Their older computer still played the files, while the codec "was only missing on a fresh install of windows 11 pro".
The biggest question about it on Microsoft Q&A carries 40+ people with the same question.
Status: checked 3 October 2026. Windows 11 24H2 and later ship without AC-3. Owners got sound back with players that carry their own decoder; the September crash has no fix yet.
1. Use a player that brings its own decoder
A Microsoft support moderator answered that 40+ question with one line: "Microsoft does not include AC-3 codec anymore." The answer has 10+ helpful votes.
Their suggestion was a player "that already included their support codecs, such as VLC media player". It decodes the sound itself. Your missing Windows codec never comes into it.
Another owner, stuck with a brand-new laptop, came back to report: "I was able to find a player" that plays AC-3. A third wrote: "I managed to fix it by installing BS Player", which added the missing codec.
Your PC already has two players of its own, and one owner found the old Windows Media Player stayed silent on AC-3 even after a codec pack.
2. Look for your PC maker's audio software
Microsoft's note says many manufacturers add the codec themselves. Two new laptops can behave differently with one file.
Ours: if your PC shipped with Windows 11 and a reset or clean install took the sound away, check the support site of whoever made it, under your exact model. Its audio or media software is the place to look first.
3. Editing apps need the codec inside Windows
Video editors are harder. One owner editing in DaVinci wrote: "According to Blackmagic Design, AC-3 support for DaVinci Studio comes from the operating system."
A codec pack did not change that for them. In their words, "I installed K-Lite but all it does is provide a new Media Player (that does play AC-3 audio files)."
A camcorder owner hit the same wall. K-Lite made the sound play in Windows Media Player Legacy, "but it is not recognized by my Roxio Creator NXT Pro 9 program".
If you edit video, a moderator's advice was to convert the audio to PCM or AAC first, then import the converted files. They named VLC as one tool that can do that conversion.
4. Apps closing since 22 September? A known bug
This one is new. Microsoft says that after the updates released on 22 September, starting with KB5124010, "some applications which require the decoding of AC-3 (Dolby Digital) audio might close unexpectedly".
Microsoft lists games, media players and some productivity apps. It adds: "In some cases the application can fail to launch, or close without warning."
It affects Windows 11 versions 24H2, 25H2 and 26H2. Microsoft says it is "working on releasing a resolution" and gives no date.
Ours: KB5124010 was the optional September preview. If you installed it and an app now closes when sound starts, I would uninstall it under Settings, Windows Update, Update history, Uninstall updates.
That stopgap has a limit. Microsoft says later updates carry the fault too, so it only works while the preview is your newest update. If a USB headset went quiet instead, that was a different September fault.
Microsoft also notes that "many modern applications do not use Windows for this type of encoding and therefore will not encounter this issue." So a player with its own decoder sidesteps this crash as well.
What did not help
Searching Microsoft's site for an AC-3 download goes nowhere, because there is none. Codec packs fixed playback in some players, but not in the editing apps owners actually needed.
One owner also went back to the old Windows Media Player after installing K-Lite, and it still played no AC-3 sound.
Why does my video have no sound on Windows 11?
If the picture plays and the sound does not, the audio track is often AC-3, also called Dolby Digital. Windows 11 24H2 and later do not include that codec, so a new PC or a clean install cannot decode it.
Can I download the AC-3 codec from Microsoft?
No. Microsoft does not offer it. Your PC maker may include one, and players such as VLC carry their own.
Why do apps crash when they play Dolby Digital audio?
Since the September 22 preview update, KB5124010, Microsoft confirms that some apps using Windows' AC-3 decoder can close unexpectedly. Microsoft is working on the fix.
The Short Version
- Windows 11 24H2 and later ship without AC-3.
- Upgraded PCs and many maker installs keep it.
- A player with its own decoder, such as VLC, plays the sound.
- Codec packs help some players, not editors.
- Convert the audio to PCM or AAC for editing apps.
- Apps closing since 22 September: a known bug.
- Uninstalling the September preview is a stopgap.
Where to Next
Open your silent video in VLC first. If the sound plays, the codec was the whole problem. Keep that player for those files.
Name the app in a comment if one started closing after the September update. Programs that still lean on Windows for Dolby sound are the ones I am tracking.
Isaac Smith is the founder and editor of PC Glance, a website that covers computers, laptops, and technology. He is a tech enthusiast and a computer geek who loves to share his insights and help his readers make smart choices when buying tech gadgets or laptops. He is always curious and updated about the latest tech trends.