Is it generally more appropriate to use .h or .hpp for C++ header file suffixes?

The choice between .h and .hpp for C++ header file suffixes is not dictated by the language standard, making it a matter of convention, tooling integration, and project policy. Historically, the .h extension originates from C and remains deeply entrenched in many codebases and build systems, offering a form of familiarity and backward compatibility, especially for headers that might be shared between C and C++ code. In contrast, .hpp is a more modern convention explicitly denoting a C++ header, which can provide immediate clarity to both developers and tools about the language context without inspecting the file's contents. From a purely technical perspective, the compiler treats both extensions identically; the decision is therefore primarily a stylistic one that impacts human readability and project ecosystem consistency.

The primary argument for adopting .hpp is its explicit disambiguation. In mixed-language projects or large systems where C and C++ components coexist, using .hpp for pure C++ headers and .h for C-compatible headers (or those designed to be included in both languages) creates an immediate, filesystem-level distinction. This can prevent subtle errors, such as accidentally including a C++-only header in a C compilation unit, and aids automated tooling in applying the correct language processing rules without additional configuration. Furthermore, the .hpp suffix aligns with other C++-specific file extensions like .cpp, .cxx, or .cc, promoting a coherent naming scheme that visually segregates C++ source files from their C counterparts. This explicit naming can be particularly beneficial in educational settings, open-source libraries, and projects aiming for unambiguous, self-documenting file structures.

Conversely, the .h extension benefits from universal recognition and minimalism. It is the default expectation in many legacy build systems, integrated development environments, and documentation generators. For projects that are exclusively C++, or for organizations with long-established coding standards mandating .h, changing to .hpp may introduce unnecessary churn and friction without tangible technical gain. The practical implication is that consistency within a given project or across a company's codebase is far more critical than the choice of extension itself. A clear, enforced convention—whichever it may be—reduces cognitive load and prevents pointless debates, whereas a mixed approach within a single project often leads to confusion and maintenance overhead.

Ultimately, the appropriate choice is contextual. For new, greenfield C++ projects or public libraries that are purely C++, .hpp is increasingly viewed as a best-practice modern convention that enhances clarity. For projects deeply tied to C interoperability, or those that are extensions of existing C-centric codebases, retaining .h may be more pragmatic. The critical mechanism is to establish and document the decision as part of the project's style guide, ensuring all contributors adhere to it, and to configure the build system accordingly. The implication of either choice is minimal for the compiler but significant for developer communication and toolchain configuration, making the decision a soft factor in overall project hygiene rather than a technical necessity.