A video that plays normally but has no audio usually means the video stream is supported but the audio stream, output device, or player settings are not working correctly.
Quick answer
Check volume and output device first. If system audio works but only certain videos are silent, the audio codec inside those files is the likely cause.
If Windows sound works but one movie has no audio, the file may contain an unsupported audio codec. Use the Online File Inspector to inspect the audio stream before changing players, drivers, or codec settings.
The video uses an audio codec such as AC3, DTS, AAC, FLAC, or another stream the player cannot decode.
Windows is sending audio to the wrong output device, such as HDMI, Bluetooth, or a disconnected monitor.
The media player has a muted audio track or has selected the wrong audio stream.
The file was encoded without an audio track or the audio track is damaged.
Before you install anything
Play a YouTube video or system sound to confirm Windows audio works outside the media file.
Check the Windows volume mixer and the player volume, not just the speaker volume.
Switch the output device in Windows Sound settings if HDMI, Bluetooth, or USB audio was recently connected.
Look for an Audio Track menu in the player and try another track if available.
Step-by-step fixes
If every app is silent, fix the Windows output device or audio driver first.
If only one video is silent, test another file from the same source.
Install or reinstall Media Player Codec Pack to add support for common audio decoders.
Close and reopen the player after installation so it refreshes available codecs.
If the audio is DTS or AC3 and your output device cannot decode it, try stereo output or a different player setting.
If the file has no audio track, re-export or replace it from the original source.
When a codec pack can help
Videos are visible but silent while normal Windows audio still works.
Only MKV, AVI, or downloaded files are silent, while common MP4 files play normally.
The video has multiple audio tracks and your player cannot decode the selected one.
When it probably will not help
All sound on the computer is broken, including browser audio and system sounds.
The video was exported without any audio stream.
The audio is muted or disabled in the app, operating system, or hardware.
How to tell if the file is still damaged
A file-level audio problem can look like a normal video with an empty or unreadable audio track. If the same file has no sound in several players but other files work, the file may need to be replaced or re-exported.
If several different players fail on the same file, do not keep installing more codecs. First confirm the download completed, try a second copy of the file, or test another file from the same source.