Microsoft Type Library

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File Format
Name Microsoft Type Library
Ontology
Extension(s) .tlb

Microsoft Type Library (TLB) files store metadata on COM (Component Object Model) APIs (interfaces, methods, data types, etc).

There are two main formats:

  • the "original format" – file starts with the bytes "SLTG". PRONOM format 1601. Additionally, the string "TYPELIB" occurs near the end of the file.
  • the "new format" – file starts with the bytes "MSFT", normally followed by the bytes 02,00,01,00 (which might be a version number) PRONOM format 1602

(PRONOM claims the TLB format is due to Borland, but that appears to be an error.)

Additionally, you will also find .TLB files which are actually in Windows PE format, and have a type library embedded as a resource. Rarely you may even encounter .TLB files for 16-bit Windows OLE which have a type library resource inside NE format.

The MSFT format is generated by the Windows CreateTypeLib2 API. Conversely, the older SLTG format is generated by the Windows CreateTypeLib API.

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