# Could introducing formal interfaces be nonbreaking?

**URL:** <https://discourse.julialang.org/t/could-introducing-formal-interfaces-be-nonbreaking/129567>\
**Category:** Internals & Design\
**Tags:** speculative\
**Created:** [June 2, 2025, 2:10pm UTC](https://discourse.julialang.org/t/could-introducing-formal-interfaces-be-nonbreaking/129567 "2025-06-02T14:10:58Z")\
**Posts on this page:** 1\
**Showing post:** 30

<div class="post-metadata">

**Author:** ![Mason](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/mason/32/2423_2.png) [@Mason](https://discourse.julialang.org/u/Mason)\
**Post date:** [June 3, 2025, 11:15am UTC](https://discourse.julialang.org/t/could-introducing-formal-interfaces-be-nonbreaking/129567/30 "2025-06-03T11:15:27Z")

</div>

The context here is that this thread was deemed off topic and split off from [Efficiency of abstract types vs `Any`](https://discourse.julialang.org/t/efficiency-of-abstract-types-vs-any/129518), where Chris’s comment mentioned [“when interfaces are added to the language”](https://discourse.julialang.org/t/efficiency-of-abstract-types-vs-any/129518/2)

Chris didn’t really get into any particular interface design there, but the mention of it piqued some interest from people, including Mateus, and another thread which was separately split off.

---

_[View the full topic](https://discourse.julialang.org/t/could-introducing-formal-interfaces-be-nonbreaking/129567)._