C17, formally ISO/IEC 9899:2018,[1] is an open standard for the C programming language, prepared in 2017 and published in July 2018.
It replaced C11 (standard ISO/IEC 9899:2011),[2] and is superseded by C23 (ISO/IEC 9899:2024) since October 2024.
[3] Since it was under development in 2017, and officially published in 2018, C17 is sometimes referred to as C18.
[4] C17 fixes numerous minor defects in C11 without introducing new language features.
For a detailed list of changes from the previous standard, see Clarification Request Summary for C11.