What is the TBK file format?
.tbk is the native document format of Asymetrix ToolBook, a Windows-based multimedia authoring and e-learning platform first released in 1990. A ToolBook "book" organizes content as a sequence of screens (pages) containing text labels, graphics, buttons, and embedded multimedia objects, all controlled by OpenScript - ToolBook's own event-driven scripting language.
Early .tbk files use a proprietary binary structure beginning with the hex sequence 03 4A 42 4F. Starting with ToolBook 9, the format adopted a PE/MZ executable wrapper, so later .tbk files open with the familiar MZ header and function as self-launching binaries that embed their own standalone player stub - no separate runtime installation is required. The newer .tbkx variant uses a ZIP-based XML container rather than the legacy binary structure.
ToolBook was a leading platform for corporate training, educational software, and CD-ROM titles throughout the 1990s and 2000s. Asymetrix sold the product to SumTotal Systems, which continued development through ToolBook 11.5 (December 2012), the final release. SumTotal issued an end-of-life notice effective December 31, 2021, recommending migration toward dominKnow and modern SCORM/xAPI content packages. Web delivery relied on the ToolBook Neuron browser plugin, which is also now defunct.
Related formats include .sbk (System Books, same underlying structure) and .tbkx (the ZIP+XML successor variant).
Security & safety
RISK: MEDIUMLater TBK files (PE/MZ wrapper) are effectively Windows executables and could theoretically carry malicious payloads. TBK files from untrusted sources should be treated with caution. Early binary TBK files (pre-v9) are data-only and lower risk.
Format details
in a nutshell- Corel Photo-Paint Backup File - Corel Photo-Paint uses .tbk as a backup/thumbnail file - completely unrelated to ToolBook.
- Toolbook Neuron (web delivery file) - TBK files served via the defunct ToolBook Neuron browser plugin for online delivery of ToolBook courses.
Programs that open TBK files
Windows1 app
ToolBook 11.5
Paid File → Open to open .tbk books in the authoring environment. EOL Dec 31 2021 - no longer sold or supported. Technical details
deep spec| Encoding | Binary (proprietary) |
| Byte order | Little-endian |
| File signature (early versions) | 03 4A 42 4F at offset 0 (ToolBook 1-8) |
| File signature (ToolBook 9+) | 4D 5A (MZ) at offset 0 - PE/MZ executable wrapper |
| Scripting language | OpenScript (ToolBook's own event-driven language) |
| Content structure | Screens (pages) containing text, graphics, buttons, and embedded multimedia objects |
| TBKX variant | ZIP-based XML container (PK magic bytes); distinct from legacy binary .tbk |
| Typical file size | 500 KB - 500 MB (varies with embedded multimedia) |
| MIME type | application/x-toolbook |
| Operating system | Windows only |
| Standalone execution | ToolBook 9+ files self-launch via embedded PE/MZ player stub - no separate runtime required |
| Web delivery method | ToolBook Neuron browser plugin (now defunct) |
| End-of-life | SumTotal issued EOL effective December 31, 2021; dominKnow recommended as migration path |
| Released | 1990 (Asymetrix ToolBook 1.0 for Windows) |
| Latest version | ToolBook 11.5 (December 2012) - final version; product EOL December 31 2021 |
TBK conversions
Community Q&A
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