IN File Extension

Have a problem opening a .IN file? We collect information about file formats and can explain what IN files are. Additionally we recommend software suitable for opening or converting such files.

What is the .IN file type?

Standing for 'input,' the .in filename extension is conventionally associated with the generic Input File (.in) file type widely used in computing and computer programming in particular. A typical input file (.in) contains initial data to served as input to a computer program, often written in C or C++. It can be either a human-readable text file or a binary blob, depending on what kind of input data is expected by a program. Input files (.in) are commonly used as a method of redirecting standard input (stdin, keyboard by default) and use a file instead of direct typing. Such input files may have arbitrary names (e.g., and a variety of internal formats.

A more specific case of using input files (.in) is represented by build templates utilized by several software development systems (e.g., Autoconf of the GNU Build System). Such templates (.in) serve the purpose of performing automated configuration actions that affect or control the build process. Here, an input file (e.g., or is a predefined template in which dynamically generated values are substituted for their placeholders to produce the actual build files like config.h.


Software to open or convert IN files

You can open IN files with the following programs: 

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