What is the BMK file format?
A .bmk file is a MovieMark bookmark created by CyberLink PowerDVD, a commercial media-playback application for Windows. It stores playback positions, scene timestamps, optional annotations, and thumbnail references for a disc or video file - but contains no video data itself.
The MovieMark feature lets users mark interesting scenes during playback and later jump directly to those positions. A .bmk file can be shared with other PowerDVD users who have the same disc or video, allowing them to navigate straight to the bookmarked scenes.
The format is proprietary to CyberLink and not publicly documented. Early versions used a binary structure; later versions may use XML internally. The file is tightly coupled to the source disc or video - moving or renaming the source breaks the bookmark link.
Corel WinDVD has historically recognized some PowerDVD bookmark files, but cross-application compatibility is limited. The .bmk extension is also used by unrelated applications, so the file's context and associated software should be checked to confirm it is a PowerDVD MovieMark file.
Security & safety
RISK: LOWBMK is a passive metadata file containing only timestamps and comments - no executable code. Safe to receive and open in PowerDVD. No known malware vectors for this format.
Format details
in a nutshellFULL NAMEPowerDVD MovieMark Bookmark Fileaka CyberLink PowerDVD bookmark, MovieMark file
DEVELOPERCyberLink Corp.since mid-2000s (CyberLink PowerDVD MovieMark feature)
CATEGORYVideo Files
MIME TYPEapplication/octet-stream
TYPEProprietary binary or XML bookmark/metadata file
This extension is also used by…
- Microsoft Help Bookmark File - Older Microsoft WinHelp/HTML Help used .bmk to store user-defined bookmarks within help files.
Programs that open BMK files
Windows2 apps
PowerDVD
Paid The native application. Open PowerDVD, then import the .bmk file via the MovieMark / Bookmark Viewer feature to jump to saved scenes. 
Technical details
deep spec| File encoding | Binary (possibly XML-structured in newer PowerDVD versions) |
| MIME type | application/octet-stream |
| Operating system | Windows only |
| Typical file size | 1 KB - 100 KB |
| Stored data | Scene timestamps, video file references, optional text annotations, thumbnail data |
| Video data stored | None - companion metadata file only; source media not embedded |
| Source coupling | Linked to a specific disc or video file; relocating or renaming the source breaks the bookmark |
| Shareability | Can be shared with other PowerDVD users with the same source disc or video for scene navigation |
| Format versioning | Not interchangeable across major PowerDVD version releases |
| Magic bytes | None publicly documented |
| Developer | CyberLink Corp. |
| Feature origin | Created by the MovieMark feature within PowerDVD during or after video playback |
| Released | mid-2000s (CyberLink PowerDVD MovieMark feature) |
| Latest version | PowerDVD 23 (2023) / PowerDVD 365 (subscription) |
| Specification | www.cyberlink.com |
BMK conversions
Not possible
Community Q&A
asked by users
M
Frequently asked questions
What is a .bmk file?
A PowerDVD MovieMark bookmark file created by CyberLink. It stores timestamps and notes for specific scenes in a movie disc or video, so you can return to them or share them with other PowerDVD users.
How do I open a .bmk file?
Install CyberLink PowerDVD and use the Bookmark Viewer feature to import the .bmk file. Without PowerDVD, you cannot meaningfully open it - it contains only timestamps referencing a video, not the video itself.
Can I convert a .bmk file to another format?
There is no useful conversion - the .bmk file is a small companion metadata file. If you want the video content it references, you need the original disc or video file.
Does WinDVD open .bmk files?
Corel WinDVD may open some CyberLink .bmk files, but compatibility is not guaranteed since the format is proprietary to PowerDVD.
References
1CyberLink PowerDVD - Bookmark Viewer helpwww.cyberlink.com
2CyberLink PowerDVD - official product pagewww.cyberlink.com
