--- title: The Mypy Blog: Mypy 1.20 Released | daily.dev description: Mypy 1.20.0 has shipped with a reworked, more aggressive and correct type narrowing engine, support for Python 3.14 t-strings (PEP 750), and an experimental... canonical: https://daily.dev/posts/the-mypy-blog-mypy-1-20-released-et3wuuepa twitter:card: summary_large_image twitter:site: @dailydotdev og:type: website og:site_name: daily.dev og:title: The Mypy Blog: Mypy 1.20 Released | daily.dev og:description: Mypy 1.20.0 has shipped with a reworked, more aggressive and correct type narrowing engine, support for Python 3.14 t-strings (PEP 750), and an experimental... og:url: https://daily.dev/posts/the-mypy-blog-mypy-1-20-released-et3wuuepa og:image: https://api.daily.dev/og/posts/et3WuuEpA.png og:image:alt: The Mypy Blog: Mypy 1.20 Released 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 Mypy Blog: Mypy 1.20 Released **[mypy - Optional Static Typing for Python](https://daily.dev/sources/mypy-lang)** · 24 min read · 0 upvotes · 0 comments ## Summary Mypy 1.20.0 has shipped with a reworked, more aggressive and correct type narrowing engine, support for Python 3.14 t-strings (PEP 750), and an experimental new Ruff-based parser. Python 3.9 support is dropped since it reached end of life, and a binary fixed-format cache plus SQLite caching are now enabled by default for faster incremental checks. The release also improves compatibility for --local-partial-types ahead of a planned default flip in mypy 2.0, renames --allow-redefinition-new handling, adds mypyc improvements (acyclic classes, faster macOS imports, new librt standard library), and removes the deprecated --force-uppercase-builtins and --force-union-syntax flags. ## Full article daily.dev links to this article rather than hosting it. Read it at the original source: ## Questions this post answers ### Does mypy 1.20 still support Python 3.9? No, mypy no longer supports running with Python 3.9 since it reached end of life, though mypy 1.20 running on Python 3.10+ can still type check code targeting Python 3.9 using the --python-version 3.9 flag. That compatibility flag itself is planned to be dropped in the first half of 2026. _Track Python version support changes like this on daily.dev before they break your CI._ ### What will change when mypy 2.0 enables --local-partial-types by default? Mypy 2.0 is planned to enable --local-partial-types by default, which will often require at least minor code changes, and mypy 1.20 significantly improves compatibility to ease that transition. It also plans to enable --strict-bytes by default and rename --allow-redefinition-new to --allow-redefinition, with --allow-redefinition-old preserving the legacy behavior. _Follow upcoming breaking changes like mypy 2.0's defaults on daily.dev before upgrading._ ### How much faster is mypy when compiled with mypyc compared to interpreted Python? Mypy compiled with mypyc runs 3 to 5 times faster than when interpreted with pure Python. Mypy 1.20 also adds mypyc-accelerated wheels for win_arm64 and Python 3.14 free-threading builds (cp314t), and introduces librt, a dedicated mypyc standard library with SIMD-optimized base64 encoding for compiled code. _Keep up with performance-focused tooling releases like mypyc on daily.dev._ ## Similar posts on daily.dev - [Elixir v1.20 released: now a gradually typed language](https://daily.dev/posts/elixir-v1-20-released-now-a-gradually-typed-language-081x31cuq) · Elixir · 4 upvotes · 0 comments - [TypeScript 6.0 is your final warning](https://daily.dev/posts/typescript-6-0-is-your-final-warning-2tbdrcemi) · Bytes by ui.dev · 144 upvotes · 15 comments - [Elixir 1.19: Faster Builds, Smarter Types, and the Year of Interoperability](https://daily.dev/posts/elixir-1-19-faster-builds-smarter-types-and-the-year-of-interoperability-0z5phajqi) · ElixirStatus · 1 upvotes · 0 comments - [Progress on TypeScript 7](https://daily.dev/posts/progress-on-typescript-7-vw602leio) · Typescript · 328 upvotes · 11 comments --- Tags: [#general-programming](https://daily.dev/tags/general-programming), [#python](https://daily.dev/tags/python), [#performance](https://daily.dev/tags/performance) [View this post on daily.dev](https://daily.dev/posts/the-mypy-blog-mypy-1-20-released-et3wuuepa) ```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 Mypy Blog: Mypy 1.20 Released","url":"https://daily.dev/posts/the-mypy-blog-mypy-1-20-released-et3wuuepa","mainEntityOfPage":{"@type":"WebPage","@id":"https://daily.dev/posts/the-mypy-blog-mypy-1-20-released-et3wuuepa"},"datePublished":"2026-08-23T12:17:26.029Z","dateModified":"2026-08-23T12:20:33.344Z","description":"Mypy 1.20.0 has shipped with a reworked, more aggressive and correct type narrowing engine, support for Python 3.14 t-strings (PEP 750), and an experimental...","image":"https://media.daily.dev/image/upload/s--HRgLpUt6--/f_auto/v1722860399/public/Placeholder%2003","thumbnailUrl":"https://media.daily.dev/image/upload/s--HRgLpUt6--/f_auto/v1722860399/public/Placeholder%2003","isAccessibleForFree":true,"articleSection":"mypy - Optional Static Typing for Python","inLanguage":"en","publisher":{"@type":"Organization","name":"daily.dev","url":"https://daily.dev","logo":{"@type":"ImageObject","url":"https://daily.dev/apple-touch-icon.png","width":180,"height":180}},"author":{"@type":"Organization","name":"mypy - Optional Static Typing for Python","logo":"https://media.daily.dev/image/upload/logos/placeholder.jpg","url":"https://daily.dev/sources/mypy-lang"},"commentCount":0,"discussionUrl":"https://daily.dev/posts/the-mypy-blog-mypy-1-20-released-et3wuuepa","interactionStatistic":[{"@type":"InteractionCounter","interactionType":{"@type":"LikeAction"},"userInteractionCount":0},{"@type":"InteractionCounter","interactionType":{"@type":"CommentAction"},"userInteractionCount":0}],"keywords":"general-programming,python,performance","timeRequired":"PT24M"} {"@context":"https://schema.org","@type":"BreadcrumbList","itemListElement":[{"@type":"ListItem","position":1,"name":"Home","item":"https://daily.dev"},{"@type":"ListItem","position":2,"name":"mypy - Optional Static Typing for Python","item":"https://daily.dev/sources/mypy-lang"},{"@type":"ListItem","position":3,"name":"The Mypy Blog: Mypy 1.20 Released"}]} {"@context":"https://schema.org","@type":"FAQPage","@id":"https://daily.dev/posts/the-mypy-blog-mypy-1-20-released-et3wuuepa#faq","mainEntity":[{"@type":"Question","name":"Does mypy 1.20 still support Python 3.9?","acceptedAnswer":{"@type":"Answer","text":"No, mypy no longer supports running with Python 3.9 since it reached end of life, though mypy 1.20 running on Python 3.10+ can still type check code targeting Python 3.9 using the --python-version 3.9 flag. 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