Table of Contents
Introduction
C++ has never been afraid of complexity—but even for a language known for performance and control, the #include system has seemed like a bygone from another era.
Modules in C++ were a long-awaited upgrade aimed at cleaning up the mess of includes, speeding up build time, and making large-scale C++ development a bit less painful.
Standardized in C++20 and expanded in C++23, modules promise big gains in compile times. But as of 2025, they’re still not as widely adopted in most teams’ toolchains. Some developers are diving in and seeing real benefits. Others are holding back, citing spotty compiler support, tricky build integration, and the reluctant to face the learning curve that comes with any paradigm shift.
This post isn’t about selling you on the latest trend or convention—it’s a practical look at what C++ modules actually offer today, where the limitations still lie, and which cases it makes sense to adopt them. Decide for yourself later on.
A Quick Primer on C++ Modules
If you’ve worked with C++ for more than five minutes, you’ve dealt with header files. They’re powerful, but can also add noise: full of macros, guard clauses, and redundant includes that slow down compilation and make dependency tracking a chore. Modules were introduced in order to alleviate some of these issues.
At a high level, C++ modules replace the traditional preprocessor-based #include model with a cleaner, more structured system. Instead of copy-pasting code into translation units, modules compile once, then import—reducing repeated parsing and giving compilers more context to optimize builds.
How C++ Modules Work
A module interface is a standalone file—usually with the .ixx extension—that declares what’s available to other parts of your program. You can then import this module in other files using the import keyword (just like how it works Python), bypassing the need for header files entirely.
Behind the scenes, the compiler builds and caches the module interface, so future builds can skip reprocessing its contents—saving time and keeping things tidy.
Timeline at a Glance
- C++20, officially published in December 2020, introduced official module support, though early compiler implementations were partial.
- C++23, released in February 2023, expanded the spec, offering better support for features like module partitions and header unit compatibility.
- Toolchains like Clang, MSVC, and GCC continue to evolve their support—but as of 2025, full interoperability is still a work in progress.
C++ module adoption timeline
Arguments for Adopting C++ Modules
If you’ve ever watched a massive C++ project crawl through compilation—or spent hours untangling a web of includes and macros—then the case for modules probably sounds pretty appealing. Here’s where they shine.
Improved Build Times and Scalability
Traditional C++ compiles every translation unit independently, parsing the same headers repeatedly across your codebase. That’s a lot of duplicated effort.
With modules, compilers can parse once and cache the results (just like how Visual Assist does it!). Module interfaces are precompiled and reused, cutting down redundant parsing.
On large projects, this can lead to significant reductions in full build and incremental compile times, especially when combined with modern build systems that understand modules.
This isn’t just theoretical—early adopters have seen real gains when porting to modules, particularly in libraries with thousands of files and deep dependency chains.
Cleaner Dependencies
Modules bring much-needed structure to C++. They reduce reliance on preprocessor directives and eliminate include guards, forward declarations, and subtle header-only bugs. In fact, they encourage you to think more clearly about what should be exposed and what should stay private.
Since you explicitly export only what’s needed, modules help enforce encapsulation, making APIs easier to maintain and less prone to unexpected breakage.
Improved IDE and Tooling Support
While not all editors are fully up to speed yet, modern IDEs and compilers are catching up. Visual Studio, Clang-based tools, and even some lightweight editors are beginning to provide meaningful module-aware features—like faster IntelliSense, smarter indexing, and fewer false-positive diagnostics.
Once your toolchain supports modules well, you’ll notice a smoother developer experience, particularly when working in large codebases.
Modernization and Future-Proofing
Adopting modules isn’t just about shaving off build minutes—it’s about aligning with the future direction of the language. As more modern C++ features lean into modules (like std::mdspan in C++23), developers who adopt early will be better positioned to take advantage of new capabilities.
Modules are also a gateway to cleaner build systems, more granular dependency management, and even more secure code, thanks to their ability to restrict symbol visibility and reduce accidental API exposure.
Industry Trends and Early Adoption
While modules haven’t reached critical mass yet, they are gaining traction. Library developers and performance-focused teams are leading the way, especially those building SDKs, game engines, or systems software where build time is a bottleneck.
We’ve also seen big names like Microsoft experiment with module adoption in parts of their standard library implementation, and some open-source projects have already migrated small parts of their code to test the waters.
Why you may want to delay adopting C++ Modules (for now)
For all the promise that C++ modules bring, real-world adoption is still, well… cautious. Developers aren’t exactly lining up to refactor their entire codebase just yet — and there are good reasons why.
Not much incentive to adopt
Even in greenfield projects, introducing modules comes with a learning curve. But in legacy codebases? Migration can be daunting. You’ll need to rethink your header structure, untangle tight coupling, and manage new build system dependencies — not to mention retraining your team. And then there’s the question of compatibility: modules don’t play nicely with everything, particularly if you rely heavily on macros, conditional compilation, or platform-specific headers.
In other words, this isn’t a weekend refactor — and for many teams, the payoff doesn’t yet outweigh the cost and it would make more sense to use modules on new projects instead.
Tooling Inconsistencies and Fragmentation
Ask any developer who’s attempted to go modular: Which compiler are you using? matters more than it should. While support for modules exists in Clang, MSVC, and GCC, it’s not uniform — and version-specific quirks can introduce frustrating inconsistencies.
Build system support is also in flux. While CMake has added module support, it still feels experimental, especially for complex project setups or cross-platform builds. Other systems like Bazel or custom build pipelines require more glue code than most teams want to maintain.
In short: the tooling isn’t fully there yet — especially if you’re not using the absolute latest compiler versions.
Lack of Ecosystem Maturity
Even if your toolchain is up to date, the broader ecosystem might not be. Most third-party libraries aren’t shipping with module interface units, which means you’re either stuck writing your own wrappers or falling back to #include anyway. That limits the benefits of going modular in mixed environments — which, let’s face it, is most environments. Until popular libraries (Boost, Qt, etc.) begin offering reliable module support, most teams can’t go all-in without making sacrifices.
Limited Real-World Case Studies
There’s still a lack of detailed success stories when it comes to large-scale adoption. Some early adopters have shared benchmarks or migration notes, but most real-world examples are small experiments, not full production shifts.
Without broader case studies to learn from, many teams are taking a “wait and see” approach — watching how others fare before diving in themselves.
Stability Concerns
The C++ modules ecosystem is still evolving. Compiler behavior can change between minor versions, module-related bugs pop up in tooling updates, and build system support continues to shift.
This kind of churn makes it hard to commit to modules in production, especially in enterprise environments where stability is everything.
Situations Where Modules Might (or Might Not) Be Worth It
C++ modules aren’t an all-or-nothing deal — and thankfully, you don’t have to rip out every #include to start using them. Depending on your project, team size, and tooling setup, modules might either be a smart optimization or an unnecessary complexity. Let’s break it down.
When Modules Make Sense
- You’re starting a new codebase (especially at scale)
Greenfield projects are the perfect playground for modern C++. If you’re building a large system from scratch, modules let you start clean — without legacy header baggage. Organizing your code as modular interfaces from the beginning can make maintenance, scalability, and onboarding much easier. - You maintain a modern toolchain
If your team is already using the latest versions of GCC, Clang, or MSVC — and you’re comfortable updating your toolchain regularly — you’re in a better position to benefit from the improved compile times and structure that modules offer. - You’re building reusable libraries
Modules are a natural fit for API design. If you’re developing shared components, SDKs, or internal packages, defining module interfaces can help enforce encapsulation and create cleaner, more predictable dependencies. - You have a strong DevOps/infrastructure team
Getting modules to play nicely with CMake or your CI pipeline isn’t always straightforward. Teams with dedicated infrastructure support can manage the learning curve more effectively and are better equipped to deal with compiler quirks or build system tweaks.
When You Might Want to Hold Off
- You’re working with a legacy codebase
Old code doesn’t like change. Migrating headers, untangling circular dependencies, and retrofitting module maps can eat up time with little visible payoff — especially if you’re also juggling deadlines. - Your build system isn’t ready
If your project relies on complex or deeply customized builds, introducing modules can introduce instability rather than speed. Even popular tools like CMake are still maturing their module support, and not all workflows are smooth yet. - You rely heavily on third-party libraries
Until widely used libraries start shipping module interface units, your modules will live in an awkward coexistence with #include. This kind of hybrid environment can be frustrating and lead to confusing bugs or duplicated efforts. - Your team is small or early-stage
If you’re moving fast and shipping often, taking time to restructure code for modules might not be worth the effort right now. Simplicity usually wins in the early days — and headers still work just fine. - Community Perspectives and Industry Signals
While C++ modules continue to mature, much of their momentum—and hesitation—comes from the wider community: compiler vendors, standards committees, open-source maintainers, and developers who’ve dipped their toes in and reported back. Let’s explore what the broader C++ ecosystem is saying about modules in 2025.
Summary: Key Considerations Before Making a Choice
As we wrap up, let’s briefly recap the main points and outline what you should consider before diving into C++ modules:
Pros of Adopting C++ Modules
- Improved build times: If you’re working with large codebases, the performance gains from reduced redundant parsing can be significant.
- Cleaner dependencies: Modules eliminate many of the headaches associated with header file inclusion, such as tangled macros and circular dependencies.
- Tooling support: While still evolving, most major compilers (MSVC, Clang, GCC) are heading in the right direction, and IDE support is growing.
Cons of Adopting C++ Modules
- Fragmented tooling: Support across compilers and build systems is still inconsistent. If you’re using a particular toolchain, check for full compatibility before diving in.
- Migration cost: Moving an existing project to modules involves significant changes in build systems, dependencies, and possibly code itself.
- Lack of third-party support: If your project relies heavily on external libraries, check whether they support modules, or be prepared for some custom workarounds.
- Limited case studies: The adoption rate of modules, especially in large-scale real-world projects, is still low, meaning the learning curve could be steeper than expected.
When Should You Adopt C++ Modules?
- New codebases or projects: If you’re starting fresh or adding new features to a project, adopting modules early could save you time in the long run.
- Open-source libraries: If you’re maintaining a widely-used library, moving to modules could lead to performance improvements that benefit the community.
- Legacy codebases: If you’re dealing with a large, established project, the effort to migrate to modules may not be justified unless you have the resources to support it.
Ultimately, adopting C++ modules in 2025 depends on your project’s size, complexity, and long-term goals. It may be worth experimenting with modules on smaller, isolated parts of your project to gauge their potential before committing to a full-scale migration.
Add more support for modules in C++
If you’re on the fence about using C++ because of the relatively limited tooling available for it, consider adding the Visual Assist plugin for Visual Studio. In a recent update, it added recognition when declaring new modules into your project. This added support makes C++ modules easier to work with with the navigation and auto suggest features working as you’d expect.
