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The EDG open source transition

What’s next for EDG

A note from John Spicer on EDG's move to open source, followed by testimonials from across the C++ community and answers to the questions EDG users are most likely to ask about the transition.

Read the note Read the testimonials Jump to the FAQ

Announcement

A note from John Spicer

Hello members of the C++ community,

I wanted to share some news about EDG and where we’re headed next.

After many years of developing and supporting EDG’s C++ front end, we’ve decided to make it open source. On September 30, 2026, the source code will be publicly available at github.com/edgcpp. The C++ Alliance, a nonprofit, will be the open-source home of the open-source project. The project will work under a fiscal sponsorship agreement, similar to how Boost operates. In addition, the C++ Alliance will explore ways in which it can facilitate EDG development going forward.

This is a significant change for EDG, and I believe it’s the right path forward. A lot has gone into this technology over the years, and it has found its way into more compilers, tools and products than I could have imagined when we started. Open source means more people in the C++ community can use it, contribute to it and help shape what comes next.

I’ll stay closely involved. I’ll chair the Fiscal Sponsorship Committee, which will oversee the project’s development alongside volunteers from the EDG user community.

For those of you who use EDG today, the first questions are likely to be practical ones: what changes, what stays the same, how the project will be maintained and what this means for you. Our FAQ answers those questions, and we’ll share more as the transition moves forward.

Everyone at EDG has worked very hard to meet, and hopefully exceed the expectations of our customers in terms of the quality of our product and the service that we have provided.

We are entering a new chapter in the life of the EDG C++ Front End. In this chapter, each of you and others in the C++ community will write what happens next.

On behalf of all of the people that have worked to make the EDG C++ Front End what it is, I hope that our users and the C++ community will take what has been produced and continue its development to stand alongside of g++ and clang as fundamental tools of the C++ world.

I also want to thank the many people who have worked with us over the years. EDG has benefited enormously from its users. That goes beyond your business to the questions, bug reports, difficult test cases and conversations that made the technology better.

I hope many of you will stay involved in this next phase. If you have questions, concerns or ideas about where EDG should go from here, please reach out.

My deepest appreciation to all of our customers for their support over the many years.

Best,
John Spicer

P.S.: EDG has had the privilege of an incredible team over the years. They are acknowledged in the cfe.c source file, but I would also like to acknowledge them here (in chronological order by start date at EDG):

  1. J. Stephen Adamczyk (founder and visionary of EDG)
  2. R. Michael Anderson
  3. Daveed Vandevoorde
  4. William M. Miller
  5. Michael J. Herrick
  6. Ellen Herrick
  7. Nina Ranns
  8. Caleb Sunstrum
  9. Wyatt Childers
  10. Christof Meerwald

Testimonials

What people are saying

Reflections on EDG and its move to open source from the C++ Alliance, the C++ standards community and EDG users.

Many C++ developers have never heard of EDG, but a lot of them have used it. It has been working quietly inside compilers and tools for decades, and it’s one of the most exacting C++ front ends there is. Now, anyone can read that code, learn from it and build on it. Our job at the C++ Alliance is to support the project, not run it. Opening EDG was President John Spicer’s decision, and he has taken real care to do it in a way that works for the people who depend on it.

Harry Bott CEO of C++ Alliance

EDG has a very special place in my heart. It was the first compiler I ever tinkered with, and I was incredibly fortunate to be given the opportunity to work on it, alongside some of the great names in the C++ community. I have enormous respect for what EDG has built over nearly four decades.

I'm delighted to see the EDG C++ Front End begin a new chapter as an open-source project, and particularly excited to see the C++ Alliance investing in its future. One of the things I have come to greatly appreciate about the Alliance is its willingness to invest in talented people and ambitious projects that can make a real contribution to the future of C++. The EDG C++ Front End feels like a natural fit for that mission.

I'm very excited to see what the Alliance and the wider C++ community can build on the extraordinary foundation EDG has created.

Nina Ranns ISO C++ committee vice convener, Standard C++ Foundation vice chair, EDG and GCC compiler engineer, C++ consultant at NMLB ltd.

I have known EDG since I became involved in C++ standardization around 1997. I have encountered its work from several vantage points: as a GCC developer who sought to bring EDG-level diagnostics to GCC, in academic research (including the early implementation of the IPR), and in industry as the architect of a product serving millions of C++ developers. I offer these thoughts in a personal capacity, drawing in part on my former work at Microsoft, not speaking for the company.

What has impressed me about EDG's front end is the quality of its engineering. It takes both the finer points of the C++ standard and the messy reality of compatibility with other compilers seriously. We sometimes joke that EDG is more compatible with other C++ front ends than those front ends are with themselves. Behind the joke is a serious achievement: engineers willing to wrestle with the hard cases, not just implement the easy ones.

I designed the IFC format and developed its specification as part of the implementation of C++20 Modules. I had the pleasure of working with EDG engineers on that effort. Their feedback was exacting, constructive, and grounded in the realities of implementing C++. Our conversations made the specification stronger. Just as memorable was the thoughtful, generous way they engaged with the work.

John Spicer's technical leadership and longstanding involvement in C++ standardization have meant a great deal to me personally. His feedback has contributed to my work on constexpr, modules, concepts, and to advocacy for safety in C++. He brings deep technical judgment to difficult questions and takes other people's ideas seriously. That combination is rare, and it has helped both the language and the people working to advance it.

I am delighted to see EDG become open source. It gives more of the C++ community a chance to learn from and to contribute to the work John and so many exceptional EDG engineers have built over the years. I look forward to what we can make possible together in this next chapter.

Gabriel Dos Reis Technical Fellow at Susquehanna International Group

Veracode depends on the EDG compiler frontend for our Static Application Security Testing (SAST) of our customers’ C++ applications. We have found it to be of the highest quality and to live up to its reputation as an industry standard.

EDG’s broad range of support for the different C++ language versions and compatibility modes with different C++ compiler vendors is invaluable in enabling us to support parsing virtually any C/C++ code from our customer base. John Spicer is a pleasure to work with and always responsive, helpful, and supportive. We are very happy to know he will be continuing to steward the EDG technology.

Bruce Duncan Director, Software Engineering at Veracode

FAQ

Frequently asked questions

What the transition means for EDG users, the code, and the people who maintain it.

  1. What changed with EDG?

    EDG’s C++ front end is now open source, with the C++ Alliance serving as the project’s nonprofit fiscal sponsor. The change opened EDG’s continued development to developers and organizations across the C++ community.

  2. Why did EDG become open source?

    EDG has played an important role supporting compilers and developer tools across the C++ ecosystem for decades. Opening the code lets more people learn from it, build on it and help shape its future.

  3. What role does the C++ Alliance play?

    The C++ Alliance gives the project a nonprofit home and supports the infrastructure and funding it needs, similar to the model the Alliance uses for Boost.

  4. Is EDG going away?

    No. EDG as a corporation is going away, but the front end has been open-sourced and will continue to be developed and be usable for a larger audience.

  5. What does this mean for current EDG users?

    The EDG C++ Front End is supported by the C++ community in the same way as g++ and clang.

  6. When did the source code become available?

    The code became available at github.com/edgcpp/compiler on September 30, 2026, under the LLVM license. Details on how to contribute will follow.

  7. Can organizations continue to build commercial products using EDG?

    Yes. The LLVM license permits commercial use, subject to its terms. Organizations with existing agreements can continue under those terms.

  8. Who maintains EDG, and how are decisions made?

    The experienced EDG engineers serve as the initial maintainers. Over time, the goal is an open process that welcomes community contributors while keeping the technical quality EDG is known for.

  9. Will EDG continue to support new C++ standards?

    Yes, with the support of the community. Standard conformance has long been one of EDG’s strengths and remains a priority. Roadmap details will be shared as they’re finalized.

  10. How can developers and current users get involved?

    Now that the repository is live, developers can report issues, contribute code and join technical discussions. Current users bring real-world experience with EDG, and their input is especially welcome. Questions and feedback can go to jhs@edg.com.

  11. Who should users contact with questions about the transition?

    Questions can be directed to jhs@edg.com. We also welcome feedback from existing users about what they would like to see as the project moves forward.