View source for Microsoft Type Library

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|subcat=Development
|extensions={{ext|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". [https://www.nationalarchives.gov.uk/PRONOM/fmt/1601 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) [https://www.nationalarchives.gov.uk/PRONOM/fmt/1602 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 [https://learn.microsoft.com/en-us/windows/win32/api/oleauto/nf-oleauto-createtypelib2 CreateTypeLib2] API. Conversely, the older SLTG format is generated by the Windows [https://learn.microsoft.com/en-us/windows/win32/api/oleauto/nf-oleauto-createtypelib CreateTypeLib] API.

== Links ==

*[https://gist.github.com/djhohnstein/e4a346ee1506895000ca0fa93e5a0024 MSFT format reverse-engineered documentation]. The original of that document is posted [http://theircorp.byethost11.com/files/TypeLib.txt here], but that version displays incorrectly due to a character encoding issue.

[[Category:Windows]]