JS with Types Start

jsconfig.json option

resolveJsonModule

  • Default false
  • Since TypeScript 2.9

resolveJsonModule lets an import (or require) of a .json file resolve, and gives the result the type of the file's contents: { "port": 8080 } becomes { port: number }. A typo in a property name is then an error like any other.

In TypeScript 5.9 it is on by default when module is nodenext, node20 or preserve, or when moduleResolution is bundler, which covers the setups on this site. With module set to node16, node18 or an es version alone, write it yourself.

At a glance

Write Usually nothing: nodenext and bundler turn it on. With other module settings, write "resolveJsonModule": true
On the command line --resolveJsonModule
Type boolean
Default in TypeScript 5.9 false (on when module is nodenext, node20 or preserve, or moduleResolution is bundler)
TypeScript's description Enable importing .json files.

The description is quoted from TypeScript's own option list (Apache-2.0); see the notices.

Examples

main.js Error confirmed 5.9.3 TypeScript 5.9.3, run 21 October 2026: main.js(4,36): error TS2339: Property 'hots' does not exist on type '{ port: number; host: string; }'. 6.0.3 TypeScript 6.0.3, run 21 October 2026: the same as 5.9.3. main.js(4,36): error TS2339: Property 'hots' does not exist on type '{ port: number; host: string; }'. 7.0.2 TypeScript 7.0.2, run 21 October 2026: the same as 5.9.3. main.js(4,36): error TS2339: Property 'hots' does not exist on type '{ port: number; host: string; }'. checked 21 October 2026 
import config from "./config.json" with { type: "json" };

console.log(`Listening on ${config.hots}:${config.port}`);error TS2339: Property 'hots' does not exist on type '{ port: number; host: string; }'.
module nodenext: the JSON file is typed, so a typo is caught.
jsconfig.json for this example 
{
  "compilerOptions": {
    "checkJs": true,
    "noEmit": true,
    "strict": true,
    "target": "es2022",
    "module": "nodenext",
    "types": []
  },
  "include": [
    "*.js"
  ]
}
main.js Error confirmed 5.9.3 TypeScript 5.9.3, run 21 October 2026: main.js(2,20): error TS2732: Cannot find module './config.json'. Consider using '--resolveJsonModule' to import module with '.json' extension. 6.0.3 TypeScript 6.0.3, run 21 October 2026: the same as 5.9.3. main.js(2,20): error TS2732: Cannot find module './config.json'. Consider using '--resolveJsonModule' to import module with '.json' extension. 7.0.2 TypeScript 7.0.2, run 21 October 2026: the same as 5.9.3. main.js(2,20): error TS2732: Cannot find module './config.json'. Consider using '--resolveJsonModule' to import module with '.json' extension. checked 21 October 2026 
import config from "./config.json";error TS2732: Cannot find module './config.json'. Consider using '--resolveJsonModule' to import module with '.json' extension.

console.log(config.port);
resolveJsonModule off with moduleResolution bundler.
jsconfig.json for this example 
{
  "compilerOptions": {
    "checkJs": true,
    "noEmit": true,
    "strict": true,
    "target": "es2022",
    "module": "esnext",
    "types": [],
    "moduleResolution": "bundler",
    "resolveJsonModule": false
  },
  "include": [
    "*.js"
  ]
}

ES modules need the json import attribute

Node.js loads a JSON file from an ES module only with an import attribute: import config from "./config.json" with { type: "json" };. Under module: "nodenext", the checker holds you to it and reports a JSON import without one (TS1543). CommonJS files load JSON with require("./config.json") and need no attribute.

main.js Error confirmed 5.9.3 TypeScript 5.9.3, run 21 October 2026: main.js(2,20): error TS1543: Importing a JSON file into an ECMAScript module requires a 'type: "json"' import attribute when 'module' is set to 'NodeNext'. 6.0.3 TypeScript 6.0.3, run 21 October 2026: the same as 5.9.3. main.js(2,20): error TS1543: Importing a JSON file into an ECMAScript module requires a 'type: "json"' import attribute when 'module' is set to 'NodeNext'. 7.0.2 TypeScript 7.0.2, run 21 October 2026: the same as 5.9.3. main.js(2,20): error TS1543: Importing a JSON file into an ECMAScript module requires a 'type: "json"' import attribute when 'module' is set to 'NodeNext'. checked 21 October 2026 
import config from "./config.json";error TS1543: Importing a JSON file into an ECMAScript module requires a 'type: "json"' import attribute when 'module' is set to 'NodeNext'.

console.log(config.port);
An ES module that imports JSON without the import attribute.
jsconfig.json for this example 
{
  "compilerOptions": {
    "checkJs": true,
    "noEmit": true,
    "strict": true,
    "target": "es2022",
    "module": "nodenext",
    "types": []
  },
  "include": [
    "*.js"
  ]
}

What type a JSON import gets

TypeScript reads the file and widens the values: strings become string, numbers number, arrays of mixed values a union. It does not keep literal values, so "port": 8080 is number, not 8080. To type a config more precisely, annotate the import's use with a @type or check it with @satisfies.

Gotchas

  • A big JSON file is read and typed on every check. For large data files that you import, a JSDoc @type on a value read with fs can be faster.
  • The typed JSON is the file as it is on disk when you check. A JSON file that changes at deploy time can differ from what was checked.

Questions

Why do I get TS2732 for a JSON import?

Your module and moduleResolution do not turn resolveJsonModule on (for example module: "node18", or a bundler setup that sets it to false). Add "resolveJsonModule": true.

  • jsconfig.json option

    module

    module tells the checker which module system your .js files follow: Node's rules with nodenext, a bundler's with preserve. Set it, even with noEmit.

  • JSDoc tag

    @type

    The JSDoc @type tag gives a variable, property or expression a type that TypeScript checks: the syntax, casts with parentheses, and whole function types.

  • JSDoc tag

    @satisfies

    The JSDoc @satisfies tag (TypeScript 5.0 and later) checks a value against a type but keeps the value's own, narrower type. When to use it instead of @type.

  • Quick start

    Node.js with ES modules

    Type-check a Node.js project written as ES modules: the jsconfig.json, @types/node, the npm scripts and the import rules that nodenext enforces.

Sources

Last reviewed 20 October 2026.