Unknown file extension ".ts" for a TypeScript file

In my opinion, this answer is best. https://stackoverflow.com/a/74608156/12894626

tldr; After years of trying to make ts-node work, just use tsx which works out of the box.

npm i -D tsx npx tsx src/index.ts 

npm: https://www.npmjs.com/package/tsx

• Has 400k weekly downloads at the time of writing and rising.

use

node --loader ts-node/esm ./my-script.ts // OR ts-node --esm ./my-script.ts 

instead of

ts-node ./my-script.ts 

MARCH 2022

USING: Node 16.6.2, ts-node v 10.7.0

What worked for me was having "type": "module" in package.json, and adding:

node --experimental-specifier-resolution=node --loader ts-node/esm ./src/app.ts 

tsconfig.json:

{ "compilerOptions": { "module": "ESNext", "esModuleInterop": true, "target": "ESNext", "moduleResolution": "Node", "outDir": "dist", "forceConsistentCasingInFileNames": true, "noFallthroughCasesInSwitch": true, "isolatedModules": false, "strict": true, "noImplicitAny": true, "useUnknownInCatchVariables": false, "inlineSourceMap": true }, "ts-node": { "esm": true }, "lib": ["esnext"] } 

N.B. The "ts-node": { "esm": true }. This seems to be the key to a lot of people's problems.

Credits to @FelipePlets for the useful answer here

EDIT You may want to use a non-esnext option, as per the ts docs:

The special ESNext value refers to the highest version your version of TypeScript supports. This setting should be used with caution, since it doesn’t mean the same thing between different TypeScript versions and can make upgrades less predictable.

Removing "type": "module" from package.json and adding:

 "compilerOptions": { "module": "CommonJS" }, 

In tsconfig.json fixed this for me.

Solution One

1. Remove "type": "module" from package.json if it's added
2. In tsconfig.json under the compilerOptions Set module property to CommonJS module: "CommonJS" and moduleResolution: "Node"

Solution Two

if the first one didn't work, or you have for some reason to keep module: "ESNext"

1- Add "type": "module" to package.json

2- Install ts-node npm i -g ts-node

3- Go to tsconfig.json and add the following:

{ "compilerOptions": { "module": "ESNext", "moduleResolution": "Node", /* ... your props ... */ }, "ts-node": { "esm": true } } 

4- Run ts-node fileName.ts

Try adding this to your tsconfig.json

"ts-node": { "esm": true, "experimentalSpecifierResolution": "node", } 

I was able to fix with a tsconfig.json that looked something like:

{ "compilerOptions": { "target": "es2022", "lib": ["ES2022"], "allowJs": true, "skipLibCheck": true, "esModuleInterop": true, "allowSyntheticDefaultImports": true, "strict": true, "forceConsistentCasingInFileNames": true, "noFallthroughCasesInSwitch": true, "module": "ES2022", "moduleResolution": "node", "resolveJsonModule": true, "isolatedModules": true, "noEmit": true, }, "exclude": [ "node_modules", ], "ts-node": { "esm": true, "experimentalSpecifierResolution": "node", } } 

I first came across this problem probably over a year ago, and ts-node has yet to fix it. None of the above solutions worked for me, and I have seemingly tried everything.

I just resorted to using tsc --outDir out file.ts and then running the file normally with node out/file.js, and then adding out to the .gitignore.

The thought behind ts-node is wonderful, just really sucks when it can't handle seemingly straightforward examples like this. Apologies the solution doesn't use ts-node, but I couldn't get it to work.

I made some changes on my package.json & tsconfig.json.Finally, it worked for me!

1. Add "type": "module" to package.json
2. Uncomment "moduleResolution": "node" section in your tsconfig.json
3. Change "module" section to "ESNEXT" in your tsconfig.json
4. Then Just Run the main script with this node --loader ts-node/esm .\index.ts

tsconfig.json

{ "compilerOptions": { /* Visit https://aka.ms/tsconfig.json to read more about this file */ /* Projects */ // "incremental": true, /* Enable incremental compilation */ // "composite": true, /* Enable constraints that allow a TypeScript project to be used with project references. */ // "tsBuildInfoFile": "./", /* Specify the folder for .tsbuildinfo incremental compilation files. */ // "disableSourceOfProjectReferenceRedirect": true, /* Disable preferring source files instead of declaration files when referencing composite projects */ // "disableSolutionSearching": true, /* Opt a project out of multi-project reference checking when editing. */ // "disableReferencedProjectLoad": true, /* Reduce the number of projects loaded automatically by TypeScript. */ /* Language and Environment */ "target": "es5", /* Set the JavaScript language version for emitted JavaScript and include compatible library declarations. */ // "lib": [], /* Specify a set of bundled library declaration files that describe the target runtime environment. */ // "jsx": "preserve", /* Specify what JSX code is generated. */ // "experimentalDecorators": true, /* Enable experimental support for TC39 stage 2 draft decorators. */ // "emitDecoratorMetadata": true, /* Emit design-type metadata for decorated declarations in source files. */ // "jsxFactory": "", /* Specify the JSX factory function used when targeting React JSX emit, e.g. 'React.createElement' or 'h' */ // "jsxFragmentFactory": "", /* Specify the JSX Fragment reference used for fragments when targeting React JSX emit e.g. 'React.Fragment' or 'Fragment'. */ // "jsxImportSource": "", /* Specify module specifier used to import the JSX factory functions when using `jsx: react-jsx*`.` */ // "reactNamespace": "", /* Specify the object invoked for `createElement`. This only applies when targeting `react` JSX emit. */ // "noLib": true, /* Disable including any library files, including the default lib.d.ts. */ // "useDefineForClassFields": true, /* Emit ECMAScript-standard-compliant class fields. */ /* Modules */ "module": "ESNEXT", // ****HERE /* Specify what module code is generated. */ // "rootDir": "./", /* Specify the root folder within your source files. */ "moduleResolution": "node", // ****HERE /* Specify how TypeScript looks up a file from a given module specifier. */ // "baseUrl": "./", /* Specify the base directory to resolve non-relative module names. */ // "paths": {}, /* Specify a set of entries that re-map imports to additional lookup locations. */ // "rootDirs": [], /* Allow multiple folders to be treated as one when resolving modules. */ // "typeRoots": [], /* Specify multiple folders that act like `./node_modules/@types`. */ // "types": [], /* Specify type package names to be included without being referenced in a source file. */ // "allowUmdGlobalAccess": true, /* Allow accessing UMD globals from modules. */ // "resolveJsonModule": true, /* Enable importing .json files */ // "noResolve": true, /* Disallow `import`s, `require`s or `<reference>`s from expanding the number of files TypeScript should add to a project. */ /* JavaScript Support */ // "allowJs": true, /* Allow JavaScript files to be a part of your program. Use the `checkJS` option to get errors from these files. */ // "checkJs": true, /* Enable error reporting in type-checked JavaScript files. */ // "maxNodeModuleJsDepth": 1, /* Specify the maximum folder depth used for checking JavaScript files from `node_modules`. Only applicable with `allowJs`. */ /* Emit */ // "declaration": true, /* Generate .d.ts files from TypeScript and JavaScript files in your project. */ // "declarationMap": true, /* Create sourcemaps for d.ts files. */ // "emitDeclarationOnly": true, /* Only output d.ts files and not JavaScript files. */ // "sourceMap": true, /* Create source map files for emitted JavaScript files. */ // "outFile": "./", /* Specify a file that bundles all outputs into one JavaScript file. If `declaration` is true, also designates a file that bundles all .d.ts output. */ // "outDir": "./", /* Specify an output folder for all emitted files. */ // "removeComments": true, /* Disable emitting comments. */ // "noEmit": true, /* Disable emitting files from a compilation. */ // "importHelpers": true, /* Allow importing helper functions from tslib once per project, instead of including them per-file. */ // "importsNotUsedAsValues": "remove", /* Specify emit/checking behavior for imports that are only used for types */ // "downlevelIteration": true, /* Emit more compliant, but verbose and less performant JavaScript for iteration. */ // "sourceRoot": "", /* Specify the root path for debuggers to find the reference source code. */ // "mapRoot": "", /* Specify the location where debugger should locate map files instead of generated locations. */ // "inlineSourceMap": true, /* Include sourcemap files inside the emitted JavaScript. */ // "inlineSources": true, /* Include source code in the sourcemaps inside the emitted JavaScript. */ // "emitBOM": true, /* Emit a UTF-8 Byte Order Mark (BOM) in the beginning of output files. */ // "newLine": "crlf", /* Set the newline character for emitting files. */ // "stripInternal": true, /* Disable emitting declarations that have `@internal` in their JSDoc comments. */ // "noEmitHelpers": true, /* Disable generating custom helper functions like `__extends` in compiled output. */ // "noEmitOnError": true, /* Disable emitting files if any type checking errors are reported. */ // "preserveConstEnums": true, /* Disable erasing `const enum` declarations in generated code. */ // "declarationDir": "./", /* Specify the output directory for generated declaration files. */ /* Interop Constraints */ // "isolatedModules": true, /* Ensure that each file can be safely transpiled without relying on other imports. */ // "allowSyntheticDefaultImports": true, /* Allow 'import x from y' when a module doesn't have a default export. */ "esModuleInterop": true, /* Emit additional JavaScript to ease support for importing CommonJS modules. This enables `allowSyntheticDefaultImports` for type compatibility. */ // "preserveSymlinks": true, /* Disable resolving symlinks to their realpath. This correlates to the same flag in node. */ "forceConsistentCasingInFileNames": true, /* Ensure that casing is correct in imports. */ /* Type Checking */ "strict": true, /* Enable all strict type-checking options. */ // "noImplicitAny": true, /* Enable error reporting for expressions and declarations with an implied `any` type.. */ // "strictNullChecks": true, /* When type checking, take into account `null` and `undefined`. */ // "strictFunctionTypes": true, /* When assigning functions, check to ensure parameters and the return values are subtype-compatible. */ // "strictBindCallApply": true, /* Check that the arguments for `bind`, `call`, and `apply` methods match the original function. */ // "strictPropertyInitialization": true, /* Check for class properties that are declared but not set in the constructor. */ // "noImplicitThis": true, /* Enable error reporting when `this` is given the type `any`. */ // "useUnknownInCatchVariables": true, /* Type catch clause variables as 'unknown' instead of 'any'. */ // "alwaysStrict": true, /* Ensure 'use strict' is always emitted. */ // "noUnusedLocals": true, /* Enable error reporting when a local variables aren't read. */ // "noUnusedParameters": true, /* Raise an error when a function parameter isn't read */ // "exactOptionalPropertyTypes": true, /* Interpret optional property types as written, rather than adding 'undefined'. */ // "noImplicitReturns": true, /* Enable error reporting for codepaths that do not explicitly return in a function. */ // "noFallthroughCasesInSwitch": true, /* Enable error reporting for fallthrough cases in switch statements. */ // "noUncheckedIndexedAccess": true, /* Include 'undefined' in index signature results */ // "noImplicitOverride": true, /* Ensure overriding members in derived classes are marked with an override modifier. */ // "noPropertyAccessFromIndexSignature": true, /* Enforces using indexed accessors for keys declared using an indexed type */ // "allowUnusedLabels": true, /* Disable error reporting for unused labels. */ // "allowUnreachableCode": true, /* Disable error reporting for unreachable code. */ /* Completeness */ // "skipDefaultLibCheck": true, /* Skip type checking .d.ts files that are included with TypeScript. */ "skipLibCheck": true /* Skip type checking all .d.ts files. */ }} 

package.json

{ "name": "async-with-ts", "version": "1.0.0", "main": "index.js", "license": "MIT", "type": "module", // ****HERE "devDependencies": { "@types/node-fetch": "^3.0.3", "ts-node": "^10.2.1", "typescript": "^4.4.2" }, "dependencies": { "node-fetch": "^3.0.0" } } 

You should be aware of using this command

node --loader ts-node/esm .\index.ts 

After some experimentation with my ts-node/puppeteer configuration I came up with this:

package.json

{ "type": "module", "scripts": { "start": "npx ts-node main.ts" }, ... } 

tsconfig.json

{ "ts-node": { "esm": true, "experimentalSpecifierResolution": "node" }, "compilerOptions": { "esModuleInterop": true, "moduleResolution": "node", "module": "ESNext", ... }, ... } 

Works great for running puppeteer in a TypeScript environment.
(Running NodeJS 19.0.0 with TypeScript 4.9.4 and ts-node 10.9.1)

I tried to remove this error by following methods but FAILED :

1. Using .mts extension.
2. Using type:commonjs instead of type:module in package.json (this will not let you use 'import' in your TS file, However i wanted that, therefore i consider this try to be failed).
3. Restarting the VS-Code

Then I tried the following and SUCCEEDED (one of them is enough):

1. Using --esm flag with ts-node command. e.g => npx ts-node --esm ./src/index.ts
2. Inside tsConfig.json, add another option after Compiler options' closing bracket named "ts-node" and set its "esm" option to "true", same as below :

{ "compilerOptions": { "module": "ESNext", "moduleResolution": "Node", /* ... other props ... */ }, "ts-node": { "esm": true, /* ... Line to be added ... */ } } 

This bug is rather amusing. I found that it is specific to Node.js version 18. To resolve it, I downgraded to Node.js version 16 using NVM. Surprisingly, the issue disappeared without requiring any modifications to my code or configuration. For those utilizing ts-node and nodemon in their development environment, I recommend downgrading to Node.js version 16 instead of using version 18.

The following worked for me :

node --loader ts-node/esm file.ts 

I had to drop ts-node because nothing was working. Thankfully, I found a better alternative that worked seamlessly. If you're still having this issue in 2024, try tsx. Worked flawlessly for me with Node v20. Used:

"tsx": "4.19.1" 

You can use ts-node-esm instead of ts-node, keeping "type":"module" in package.json, and using import './module.js' in your .ts files.

Related: https://github.com/TypeStrong/ts-node/issues/1007

UPDATE:

This answer has an even better solution as allows to import modules without .js extension:

https://stackoverflow.com/a/65163089/1482990

Running ts-node with --esm worked for me.

For example:

ts-node --esm src/App.ts 

That error is caused by trying to import modules, which without the ES Modules flag, ts-node doesn't support.

Upgrading from [email protected] to [email protected] generated this error when running tests using mocha:

npx mocha -r ts-node/register --reporter list --recursive src/test/**.

Fix (currently) is to rollback to [email protected].

all i had to do is install vite-node and execute the following script. stupid simple!

 "dev": "vite-node --watch src/index.ts", 

found here: https://github.com/TypeStrong/ts-node/issues/1997#issuecomment-2405925074

Well it is almost 2025 and I still can't do node --watch ./just-do-it.ts while I can do bun --watch ./just-do-it.ts

so my answer is use BunJs if you don't need to use NodeJs

bun --watch ./just-do-it.ts

I followed advice given herein. I also had to uninstall lodash-es and install lodash instead to make it work.

if your tsconfig.json contains "module": "ESNext". I have used the below script in my package.json. It worked.

 "start": "nodemon -e ts -w ./src -x npm run watch:serve", "watch:serve": "node --loader ts-node/esm src/server.ts", 

Some packages needs ES Modules. In my case I was using @Auth/core library which was internally using ES modules instead of CommonJS. So, to resolve this error. I follwed these steps.

Step#1

Upgraded Node to v19 or greater. (In my case node18 was causing error. So, I upgraded to node19)

NODE --> v19.9.0 NPM --> v9.6.3 

Step#2

In package.json add "type"= "module" e.g

{ ... "author": "", "type": "module", <--- * Add this "license": "ISC", ... } 

Step#3

In tsconfig.json file add ts-node property. e.g

{ "compileOnSave": true, "compilerOptions": { ... "target": "ESNext", "lib": ["ESNext", "esnext.asynciterable"], "emitDecoratorMetadata": true, "moduleResolution": "node", "module": "ESNext", ... }, "ts-node": { // "esm": true, <--- Tell ts-node CLI to install the --loader automatically }, "include": ["src/**/*.ts", "src/**/*.json", ".env"], "exclude": ["node_modules", "src/http", "src/logs"] } 

Step#4 Update All imports (Or you can try to solve it in a better way)

Import files with exact path and extension(e.g file_name.ts). e.g

import { UserController } from '../controllers/user.controller.ts'; 

.

Note:- I was getting error with nodemon for development. For that my exec command was

"exec": "ts-node -r tsconfig-paths/register --transpile-only src/server.ts" 

Try a different version of node. It works okay for version 19 on my machine, but not on 21.

There is an incompatibility between es modules and some versions of node. See the related Github issue

1.Setup tsconfig.json file

{ "compilerOptions": { "target": "ESNext", "module": "ESNext", "rootDir": "./src", "outDir": "./dist", "esModuleInterop": true, "moduleResolution": "node", "skipLibCheck": true, "forceConsistentCasingInFileNames": true, "strict": true }, "include": ["src/**/*.ts"], "exclude": ["node_modules"] } 

2. create a nodemon.json file

{ "watch": ["src"], "ext": "ts", "exec": "ts-node --esm ./src/server.ts" } 

3. setup package.json file

{ "name": "your-project-name", "version": "1.0.0", "main": "dist/server.js", "type": "module", "scripts": { "dev": "nodemon" }, 

4. Now , finally run npm run dev

remove type : "module" from package.json and you are good to go.

July 2022, with the use of ts-node

Node 16.14.2, ts-node 10.8.2

First install ts-node and base configuration

npm install ts-node --save-dev npm install @tsconfig/node16 --save-dev 

tsconfig.json:

{ "extends": "@tsconfig/node16/tsconfig.json", "compilerOptions": { "resolveJsonModule": true }, "include": [ "main.ts" // here you can include another directories with sources ], "exclude": [ "node_modules" ] } 

You can remove everything related to modules/compilation from package.json.

And then you can run your program as

ts-node ./main.ts 

For me (node version 14), for some reason, the problem was that I install the serialize-error package and when I tried to import it to threw that error. To solve it I downgraded the version of the package from 11.0.0 to 8.0.0.

If you use PowerShell on VS Code on Windows 11 try to use this command:

ts-node-esm.cmd .\my_script.ts

after this solution: https://stackoverflow.com/a/62099904/8967481

For anyone who is running into this issue while trying run an script in an NX project.

# For apps ts-node --project tsconfig.app.json $yourFilePath # For libraries ts-node --project tsconfig.lib.json $yourFilePath # For tests ts-node --project tsconfig.spec.json $yourFilePath 

@vadimk7 wasn't far off, my solution was to change my file extension to .mts and then use ts-node-esm myfile.mts