--- title: Stop using "as" in TypeScript. Try "satisfies" | daily.dev description: A comparison of TypeScript's `as` type assertion versus the `satisfies` operator, showing how `satisfies` validates an object against a type while preserving... canonical: https://daily.dev/posts/ti9v9gi21 twitter:card: summary_large_image twitter:site: @dailydotdev og:type: website og:site_name: daily.dev og:title: Stop using "as" in TypeScript. Try "satisfies" | daily.dev og:description: A comparison of TypeScript's `as` type assertion versus the `satisfies` operator, showing how `satisfies` validates an object against a type while preserving... og:url: https://daily.dev/posts/ti9v9gi21 og:image: https://api.daily.dev/og/posts/tI9v9GI21.png og:image:alt: Post cover image 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. # Stop using "as" in TypeScript. Try "satisfies" **[Lonely Programmer](https://daily.dev/sources/lonely_programmer)** · [@andradei](https://daily.dev/andradei) · 83 upvotes · 3 comments ## Summary A comparison of TypeScript's `as` type assertion versus the `satisfies` operator, showing how `satisfies` validates an object against a type while preserving its literal, narrower types. An example demonstrates that `as` causes TypeScript to widen properties to the union type (losing specificity), while `satisfies` retains the exact inferred types so methods like string or tuple operations work without additional casts. Requires TypeScript 4.9 or later. ## Full article daily.dev links to this article rather than hosting it. Read it at the original source: ## Community discussion Top comments from developers on daily.dev. **@zalimitless** · 7 upvotes > "as" isn't as satisfying as "satisfies". > Checks out. **@ahmetozel** · 0 upvotes > The “keep what I wrote” framing is especially useful for configuration maps, where callers need the actual property keys and value shapes. One boundary worth making explicit is mutability: satisfies does not make an object readonly. If the configuration is meant to be immutable, that is a separate choice, often expressed with as const together with a compatible readonly target type. > > For a public function, preserving every implementation detail is not always desirable either. An explicit return annotation can deliberately expose a stable contract while hiding extra fields. I would choose... **@ristotoldsep** · 0 upvotes > `satisfies` is one of TypeScript’s rare “oh, that’s actually nicer” features. --- Tags: [#typescript](https://daily.dev/tags/typescript) [View this post on daily.dev](https://daily.dev/posts/ti9v9gi21) ```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":"DiscussionForumPosting","mainEntityOfPage":"https://daily.dev/posts/ti9v9gi21","headline":"Stop using \"as\" in TypeScript. 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One boundary worth making explicit is mutability: satisfies does not make an object readonly. If the configuration is meant to be immutable, that is a separate choice, often expressed with as const together with a compatible readonly target type.\nFor a public function, preserving every implementation detail is not always desirable either. An explicit return annotation can deliberately expose a stable contract while hiding extra fields. I would choose satisfies for validating the implementation’s shape and the return type for deciding what callers are allowed to depend on.","datePublished":"2026-10-06T18:34:06.081Z","url":"https://daily.dev/posts/tI9v9GI21#c-4Vjx0IT95","author":{"@type":"Person","name":"Ahmet Özel","url":"https://daily.dev/ahmetozel","image":"https://avatars.githubusercontent.com/u/70992231?v=4"}},{"@type":"Comment","text":"satisfies is one of TypeScript’s rare “oh, that’s actually nicer” features.","datePublished":"2026-10-05T12:28:13.503Z","url":"https://daily.dev/posts/tI9v9GI21#c-3b7VlH8fF","author":{"@type":"Person","name":"Risto Tõldsep","url":"https://daily.dev/ristotoldsep","image":"https://lh3.googleusercontent.com/a/ACg8ocLDWc6mZn0JwNmXXw6WY0L_HJ6pegzRttooC5VgtXESHSj3MNYx=s96-c"}}],"isPartOf":{"@type":"WebPage","url":"https://daily.dev/squads/lonely_programmer","name":"Lonely Programmer"}} {"@context":"https://schema.org","@type":"BreadcrumbList","itemListElement":[{"@type":"ListItem","position":1,"name":"Home","item":"https://daily.dev"},{"@type":"ListItem","position":2,"name":"Lonely Programmer","item":"https://daily.dev/squads/lonely_programmer"},{"@type":"ListItem","position":3,"name":"Stop using \"as\" in TypeScript. 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