What Is a Static Library?

A static library is a computer archive that holds a group of related files for easy linking into programs. The contents of this library are usually machine code files that are not readable by humans. These machine code files are normally generated from code compilation or a similar process. Most operating systems have standard extensions for static libraries, so they are easy to identify regardless of size or content.

The two different kinds of computer libraries are static and dynamic. A static library is more flexible than a dynamic library because its exact path is irrelevant to the executable that uses it. Static libraries are linked into an executable file and can then be deleted if necessary because their content has been included in the final program. A dynamic library cannot be deleted because its content is loaded as the executable runs, so its locations relative to the executable and in the operating system are important. Static linking allows a library to be moved or reused without concern for absolute location paths.

In contrast to a dynamic library, a static library is not usually executable on its own. In C++, static libraries often act like large object files, and they can be linked into executables in the same way object files can and then be deleted without detriment to the program. Although it is often possible to forgo a static library, they are often useful in terms of organization. For both users and developers, it is usually easier to have a single file containing related material than to have many small files. Many developers build static libraries specifically for this organizational benefit.

Building a static library is much simpler than building a dynamic library. The contents of static libraries are not linked together because they are not expected to run on their own, so a simple archiver is usually enough to create them. Creating a static library that does not link properly within itself is not inherently dangerous as long as the library is linked with any other external files that may be necessary. A library can depend on an external group of object files, or one library can depend on another. The use and organization of static libraries is often a personal choice on the part of the programmer rather than a requirement, although their inherent mobility often makes them a desirable choice.