--- title: The C++26 inplace_vector container | daily.dev description: C++26 introduces std::inplace_vector, a container with compile-time fixed capacity like std::array but a runtime variable size like std::vector. Its elements... canonical: https://daily.dev/posts/the-c-26-inplace-vector-container-gssfcflxu twitter:card: summary_large_image twitter:site: @dailydotdev og:type: website og:site_name: daily.dev og:title: The C++26 inplace_vector container | daily.dev og:description: C++26 introduces std::inplace_vector, a container with compile-time fixed capacity like std::array but a runtime variable size like std::vector. Its elements... og:url: https://daily.dev/posts/the-c-26-inplace-vector-container-gssfcflxu og:image: https://api.daily.dev/og/posts/gsSfCFlxu.png og:image:alt: The C++26 inplace_vector container og:image:width: 1200 og:image:height: 630 og:locale: en --- > ## Documentation Index > Fetch the complete documentation index at: https://daily.dev/llms.txt > Use this file to discover all available pages before exploring further. # The C++26 inplace_vector container **[Marius Bancila](https://daily.dev/sources/mariusbancila)** · 5 min read · 0 upvotes · 0 comments ## Summary C++26 introduces std::inplace_vector, a container with compile-time fixed capacity like std::array but a runtime variable size like std::vector. Its elements are stored in-place and only constructed when added, so the element type doesn't need to be default-constructible. It offers three insertion modes: push_back/emplace_back which throw on overflow, try_push_back/try_emplace_back which return nullptr on failure, and unchecked_push_back/unchecked_emplace_back which are UB if capacity is exceeded. It suits cases where a fixed upper bound is known and heap allocation should be avoided, such as embedded, real-time, and low-latency code, with pathfinding neighbor buffers capped at 8 elements per cell as an example. ## Full article daily.dev links to this article rather than hosting it. Read it at the original source: ## Questions this post answers ### What is std::inplace_vector in C++26 and how is it different from std::array and std::vector? std::inplace_vector is a C++26 container with compile-time fixed capacity like std::array but a runtime variable size like std::vector. Its elements are stored contiguously in-place, wherever the container itself lives (stack, heap, or static storage), and are constructed only when added, so the element type doesn't need to be default-constructible, unlike std::array. _Developers adopting new C++26 containers can track changes like this one on daily.dev._ ### What happens when you push_back onto a full std::inplace_vector? Calling push_back or emplace_back on a full std::inplace_vector throws std::bad_alloc since capacity cannot grow. Two alternatives exist: try_push_back and try_emplace_back return nullptr on failure and leave the container unchanged, while unchecked_push_back and unchecked_emplace_back skip the check entirely, requiring size() < capacity() as a precondition and causing undefined behavior if violated. _Developers choosing between safe and unchecked insertion APIs can reference comparisons like this on daily.dev._ ### When should I use std::inplace_vector instead of std::vector in C++? Use std::inplace_vector when there's a known fixed upper bound on element count and heap allocation should be avoided, such as embedded or freestanding environments, real-time or low-latency code, small temporary buffers in hot loops, or fixed-size data embedded in structs or shared memory. An example is storing up to 8 grid-cell neighbors in pathfinding code like A* without per-call heap allocation. _Engineers deciding between container types for performance-critical code can find cases like this on daily.dev._ ## Similar posts on daily.dev - [C\+\+26: std::inplace\_vector](https://daily.dev/posts/c-26-std-inplace-vector-9a9stjxez) · Sandor Dargo · 2 upvotes · 0 comments - [Part 1: std::inplace\_vector — The Fixed-Capacity Vector Finally Comes to C\+\+26](https://daily.dev/posts/part-1-std-inplace-vector-the-fixed-capacity-vector-finally-comes-to-c-26-obybukog4) · Towards Dev · 0 upvotes · 0 comments - [A quick C\+\+ standard container overview](https://daily.dev/posts/a-quick-c-standard-container-overview-wo9xy03gi) · Meeting C\+\+ · 0 upvotes · 0 comments - [Implementing vector](https://daily.dev/posts/implementing-vector-b9b7cs263) · C\+\+ · 4 upvotes · 0 comments - [C\+\+26: std::hive](https://daily.dev/posts/c-26-std-hive-umqdxdqhq) · Sandor Dargo · 2 upvotes · 0 comments --- Tags: [#c++](https://daily.dev/tags/c++), [#data-structures](https://daily.dev/tags/data-structures) [View this post on daily.dev](https://daily.dev/posts/the-c-26-inplace-vector-container-gssfcflxu) ```json {"@context":"https://schema.org","@graph":[{"@type":"Organization","@id":"https://daily.dev/#organization","name":"daily.dev","url":"https://daily.dev","logo":{"@type":"ImageObject","url":"https://daily.dev/apple-touch-icon.png","width":180,"height":180},"sameAs":["https://twitter.com/dailydotdev","https://github.com/dailydotdev","https://www.linkedin.com/company/daily-dev-ltd"]},{"@type":"WebSite","@id":"https://daily.dev/#website","url":"https://daily.dev","name":"daily.dev","publisher":{"@id":"https://daily.dev/#organization"},"potentialAction":{"@type":"SearchAction","target":{"@type":"EntryPoint","urlTemplate":"https://daily.dev/search?q={search_term_string}"},"query-input":"required name=search_term_string"}}]} {"@context":"https://schema.org","@type":"TechArticle","headline":"The C++26 inplace_vector container","url":"https://daily.dev/posts/the-c-26-inplace-vector-container-gssfcflxu","mainEntityOfPage":{"@type":"WebPage","@id":"https://daily.dev/posts/the-c-26-inplace-vector-container-gssfcflxu"},"datePublished":"2026-10-24T21:01:18.803Z","dateModified":"2026-10-24T21:01:55.519Z","description":"C++26 introduces std::inplace_vector, a container with compile-time fixed capacity like std::array but a runtime variable size like std::vector. 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