--- title: "TIL: TypeScript satisfies Keeps Your Object's Keys" description: The TypeScript satisfies operator checks an object against a type but keeps its real key names, so a typo in a key becomes a compile error. canonical: https://lukeocodes.dev/til-typescript-satisfies type: article locale: en_GB published: 2026-11-03T00:00:00.000Z modified: 2026-11-03T00:00:00.000Z authors: - Luke Oliff section: TIL tags: - TIL - TypeScript - satisfies - type checking - typescript 4.9 feed: https://lukeocodes.dev/rss.xml search: https://lukeocodes.dev/search.json?q={query} schema: - "@context": https://schema.org "@graph": - "@type": WebSite "@id": https://lukeocodes.dev/#website url: https://lukeocodes.dev name: Luke Oliff alternateName: lukeocodes inLanguage: en publisher: "@id": https://lukeocodes.dev/authors/luke#person description: Personal blog and writing by Luke Oliff — developer relations, voice AI, developer experience. potentialAction: - "@type": SearchAction target: "@type": EntryPoint urlTemplate: https://lukeocodes.dev/blog/search?q={search_term_string} query-input: required name=search_term_string - "@type": Person "@id": https://lukeocodes.dev/authors/luke#person name: Luke Oliff url: https://lukeocodes.dev/authors/luke description: Engineer and developer relations leader. Writing about developer relations, AI, and the voice industry, from the UK. mainEntityOfPage: https://lukeocodes.dev/authors/luke givenName: Luke familyName: Oliff image: https://lukeocodes.dev/authors/luke.jpg jobTitle: Engineer and developer relations leader sameAs: - https://www.linkedin.com/in/lukeocodes - https://github.com/lukeocodes - https://bsky.app/profile/lukeocodes.dev - https://x.com/lukeocodes - https://hashnode.com/@lukeocodes - https://dev.to/lukeocodes knowsAbout: - Developer Relations - Developer Experience - Voice AI - Text-to-Speech - Answer Engine Optimisation - Search Engine Optimisation - Open Source - Developer Tooling - API Design - Speech-to-Text - Voice Agents - Community Building knowsLanguage: - English nationality: British alumniOf: - "@type": Organization name: The Open University - "@context": https://schema.org "@graph": - "@type": Person "@id": https://lukeocodes.dev/authors/luke#person name: Luke Oliff url: https://lukeocodes.dev/authors/luke description: Engineer and developer relations leader. Writing about developer relations, AI, and the voice industry, from the UK. mainEntityOfPage: https://lukeocodes.dev/authors/luke givenName: Luke familyName: Oliff image: https://lukeocodes.dev/authors/luke.jpg jobTitle: Engineer and developer relations leader sameAs: - https://www.linkedin.com/in/lukeocodes - https://github.com/lukeocodes - https://bsky.app/profile/lukeocodes.dev - https://x.com/lukeocodes - https://hashnode.com/@lukeocodes - https://dev.to/lukeocodes knowsAbout: - Developer Relations - Developer Experience - Voice AI - Text-to-Speech - Answer Engine Optimisation - Search Engine Optimisation - Open Source - Developer Tooling - API Design - Speech-to-Text - Voice Agents - Community Building knowsLanguage: - English nationality: British alumniOf: - "@type": Organization name: The Open University - "@type": BlogPosting "@id": https://lukeocodes.dev/til-typescript-satisfies#article headline: "TIL: TypeScript satisfies Keeps Your Object's Keys" alternativeHeadline: "TIL: TypeScript satisfies Checks Your Object and Keeps Its Keys" description: The TypeScript satisfies operator checks an object against a type but keeps its real key names, so a typo in a key becomes a compile error. datePublished: 2026-11-03T00:00:00.000Z dateModified: 2026-11-03T00:00:00.000Z url: https://lukeocodes.dev/til-typescript-satisfies mainEntityOfPage: https://lukeocodes.dev/til-typescript-satisfies inLanguage: en author: - "@id": https://lukeocodes.dev/authors/luke#person isPartOf: "@id": https://lukeocodes.dev/#website keywords: TIL, TypeScript, satisfies, type checking, typescript 4.9 articleSection: TIL abstract: "The TypeScript satisfies operator, added in TypeScript 4.9, checks a value against a type without replacing the type TypeScript worked out for it. Write satisfies Record after the object instead of : Record before it, and a typo like routes.hoem fails to compile." speakable: "@type": SpeakableSpecification cssSelector: - .post-tldr - h1 image: https://lukeocodes.dev/og.png?h=TIL%3A+TypeScript+satisfies+Keeps+Your+Object%27s+Keys&d=The+TypeScript+satisfies+operator+checks+an+object+against+a+type+but+keeps+its+real+key+names%2C+so+a+typo+in+a+key+becomes+a+compile+error.&e=Writing wordCount: 222 timeRequired: PT2M publisher: "@id": https://lukeocodes.dev/authors/luke#person - "@type": BreadcrumbList itemListElement: - "@type": ListItem position: 1 name: Home item: https://lukeocodes.dev - "@type": ListItem position: 2 name: Writing item: https://lukeocodes.dev/blog - "@type": ListItem position: 3 name: "TIL: TypeScript satisfies Keeps Your Object's Keys" item: https://lukeocodes.dev/til-typescript-satisfies --- [Luke Oliff.](/) - [Blog](/blog) - [CV](/cv) - [Uses](/uses) - [User manual](/user-manual) - [Living with ADHD](/living-and-working-with-adhd) - [RSS](/rss.xml) [Luke Oliff · Writing](/blog) # TIL: TypeScript satisfies Checks Your Object and Keeps Its Keys Nov 2026 · [TIL](/blog/category/til) · 2 min read · [Luke Oliff](/authors/luke) **TL;DR:** The TypeScript satisfies operator, added in TypeScript 4.9, checks a value against a type without replacing the type TypeScript worked out for it. Write satisfies Record after the object instead of : Record before it, and a typo like routes.hoem fails to compile. `satisfies` checks an object against a type and keeps everything TypeScript already knows about it. The TypeScript satisfies operator came in with [TypeScript 4.9](https://www.typescriptlang.org/docs/handbook/release-notes/typescript-4-9.html). The old way puts a type annotation (the `: Type` after the name) on the variable. `Record` means an object with any string as a key and a `Route` as each value: ```ts type Route = { path: string; auth?: boolean }; const routes: Record = { home: { path: "/" }, admin: { path: "/admin", auth: true }, }; routes.hoem; // no error ``` The annotation says any string is a valid key, so the typo gets through. Move the type to the end with `satisfies`: ```ts const routes = { home: { path: "/" }, admin: { path: "/admin", auth: true }, } satisfies Record; routes.hoem; // error: Property 'hoem' does not exist ``` With TypeScript satisfies, every route still has to have a `path`. TypeScript just keeps the two real key names, `home` and `admin`, as well. ## When to use TypeScript satisfies instead of as `as` tells the compiler (the tool that checks your types) to trust you, so `{ home: {} } as Record` gets through with no `path` at all. Use TypeScript satisfies when you want the check, and `as` only when you know something the compiler can't. [All posts](/blog) → ## Search this site `GET https://lukeocodes.dev/search.json?q=` returns matching posts as JSON, each with its page URL and its markdown URL. Add `&limit=<1-50>` for more than 10. 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