CTH File

What are CTH files and how to open them

Are you having problems opening a CTH file or are you simply curious about its contents? We're here to explain the properties of these files and provide you with software that can open or handle your CTH files.

What is a CTH file?

A .CTH file is a Wintertree Thesaurus Engine DB file.

Wintertree Thesaurus Engine DB is a proprietary compiled thesaurus database used by the Wintertree Thesaurus Engine (formerly called ThesDB). It provides fast, read-only access to categories of synonyms, antonyms, and related word terms for developers building applications that need thesaurus lookups.

The main use of this database is to supplement software with thesaurus‐capabilities. The Wintertree SDKs (Windows, Java, source code) include this database and accompanying API functions so developers' applications can query synonyms, antonyms, category names, and term lists. A text‐format version of a thesaurus file (editable by users) can be compiled by the engine into this binary form.

Internally, compiled files start with the ASCII marker ThesDBThesaurus at byte offset zero. They also include strings such as WINTERTREE SOFTWARE INC. and THESDB THESAURUS somewhere in the file, which helps tools identify legitimate Wintertree compiled thesaurus databases.

How to open CTH files

Important: Different programs may use files with the CTH file extension for different purposes, so unless you are sure which format your CTH file is, you may need to try a few different programs.

While we have not verified the app ourselves yet, our users have suggested a single CTH opener which you will find listed below.

Last updated: September 19, 2026

Various apps that use files with this extension

These apps are known to open certain types of CTH files. Remember, different programs may use CTH files for different purposes, so you may need to try out a few of them to be able to open your specific file.

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File.org helps thousands of users every day, and we would love to hear from you if you have additional information about CTH file formats, example files, or compatible programs. Please use the links below or email us at submit@file.org to discuss further.