The quick explanation
Reddit-hosted media can be delivered as separate adaptive video and audio streams. A browser or simple “Save video as” command may capture only the visible video stream. The picture works, but the matching audio never entered the file.
How Save Video Online handles it
The analyser checks the Reddit post rather than blindly saving the first MP4 it sees. When compatible video and audio streams are available, the conversion job downloads both and uses FFmpeg to merge them into one finished file. The progress screen tells you when merging is occurring.
Check whether the original post actually has sound
Play the post in Reddit with your device volume up and the player unmuted. Some posts are genuinely silent, GIF-style loops or externally embedded media. A downloader cannot restore audio that never existed in the source.
Use the post URL, not only the media URL
A bare v.redd.it address may not include all the context needed to locate the matching audio. The complete reddit.com post URL is usually the best input because it lets the extractor inspect the post metadata and media variants.
What to do when the finished file is still silent
Try the full post URL, choose Compatible MP4, and confirm the post plays with sound in an incognito browser. When the post requires a login, has been deleted or exposes only video, the service cannot lawfully or technically manufacture the missing stream.
Practical checklist
- Use the complete individual Reddit post URL.
- Confirm the post itself plays with sound.
- Choose Compatible MP4 rather than a bare original stream.
- Allow the merge stage to finish before closing the page.
- Test the completed file in another media player if your default player is muted.