diff --git a/.github/workflows/run-tests.yml b/.github/workflows/run-tests.yml
index 428c3044..3ed5179f 100644
--- a/.github/workflows/run-tests.yml
+++ b/.github/workflows/run-tests.yml
@@ -21,7 +21,8 @@ jobs:
         with:
           node-version: ${{ matrix.node-version }}
           check-latest: true
-      - run: npm i
+          cache: npm
+      - run: npm ci
       - run: npm run test:coverage
         env:
           CI: true
diff --git a/.github/workflows/typecheck.yml b/.github/workflows/typecheck.yml
new file mode 100644
index 00000000..c20b98a0
--- /dev/null
+++ b/.github/workflows/typecheck.yml
@@ -0,0 +1,23 @@
+name: Typecheck
+
+on:
+  pull_request:
+  push:
+    branches: [master]
+
+jobs:
+  typecheck:
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v4
+      - name: Use Node.js 24.x
+        uses: actions/setup-node@v4
+        with:
+          node-version: 24
+          check-latest: true
+          cache: npm
+      - run: npm ci
+      - run: npm run typecheck
+        env:
+          CI: true
diff --git a/benchmarks/benchmark.js b/benchmarks/benchmark.js
index 4edfda7f..d2c7ba6a 100644
--- a/benchmarks/benchmark.js
+++ b/benchmarks/benchmark.js
@@ -1,4 +1,4 @@
-import { fdir } from "../src/index";
+import { fdir } from "../src/index.ts";
 import { fdir as fdir5 } from "fdir5";
 import { fdir as fdir4 } from "fdir4";
 import fdir3 from "fdir3";
@@ -17,7 +17,7 @@ import { getAllFilesSync, getAllFiles } from "get-all-files";
 import packageJson from "../package.json";
 import { readFileSync, readdirSync, writeFileSync } from "fs";
 import CSV2MD from "csv-to-markdown-table";
-import { getSystemInfo } from "./export";
+import { getSystemInfo } from "./export.ts";
 import { readdir } from "fs/promises";
 
 async function benchmark() {
diff --git a/benchmarks/fdir-benchmark.ts b/benchmarks/fdir-benchmark.ts
index bfa6ea99..1f25c863 100644
--- a/benchmarks/fdir-benchmark.ts
+++ b/benchmarks/fdir-benchmark.ts
@@ -1,5 +1,5 @@
 import child_process from "child_process";
-import { Fdir } from "../src/index";
+import { Fdir } from "../src/index.ts";
 import b from "benny";
 
 type Version = (typeof versions)[number] | "current";
diff --git a/benchmarks/glob-benchmark.ts b/benchmarks/glob-benchmark.ts
index acaac5da..1f50c749 100644
--- a/benchmarks/glob-benchmark.ts
+++ b/benchmarks/glob-benchmark.ts
@@ -1,4 +1,4 @@
-import { fdir } from "../src/index";
+import { fdir } from "../src/index.ts";
 import { glob, globSync } from "glob";
 import fg from "fast-glob";
 import tg from "tiny-glob";
diff --git a/package-lock.json b/package-lock.json
index ab6ec006..0448dc83 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -41,7 +41,7 @@
         "tiny-glob": "^0.2.9",
         "ts-node": "^10.9.1",
         "tsdown": "^0.12.5",
-        "typescript": "^5.3.2",
+        "typescript": "^5.8.3",
         "vitest": "^0.34.6",
         "walk-sync": "^3.0.0"
       },
@@ -4393,10 +4393,11 @@
       }
     },
     "node_modules/typescript": {
-      "version": "5.3.2",
-      "resolved": "https://registry.npmjs.org/typescript/-/typescript-5.3.2.tgz",
-      "integrity": "sha512-6l+RyNy7oAHDfxC4FzSJcz9vnjTKxrLpDG5M2Vu4SHRVNg6xzqZp6LYSR9zjqQTu8DU/f5xwxUdADOkbrIX2gQ==",
+      "version": "5.8.3",
+      "resolved": "https://registry.npmjs.org/typescript/-/typescript-5.8.3.tgz",
+      "integrity": "sha512-p1diW6TqL9L07nNxvRMM7hMMw4c5XOo/1ibL4aAIGmSAt9slTE1Xgw5KWuof2uTOvCg9BY7ZRi+GaF+7sfgPeQ==",
       "dev": true,
+      "license": "Apache-2.0",
       "bin": {
         "tsc": "bin/tsc",
         "tsserver": "bin/tsserver"
diff --git a/package.json b/package.json
index 70f4d252..6cd0ab75 100644
--- a/package.json
+++ b/package.json
@@ -8,6 +8,7 @@
   "scripts": {
     "prepublishOnly": "npm run test && npm run build",
     "build": "tsdown",
+    "typecheck": "tsc",
     "format": "prettier --write src __tests__ benchmarks",
     "test": "vitest run __tests__/",
     "test:coverage": "vitest run --coverage __tests__/",
@@ -77,7 +78,7 @@
     "tiny-glob": "^0.2.9",
     "ts-node": "^10.9.1",
     "tsdown": "^0.12.5",
-    "typescript": "^5.3.2",
+    "typescript": "^5.8.3",
     "vitest": "^0.34.6",
     "walk-sync": "^3.0.0"
   },
diff --git a/src/api/async.ts b/src/api/async.ts
index 11bb1add..0af39981 100644
--- a/src/api/async.ts
+++ b/src/api/async.ts
@@ -1,5 +1,5 @@
-import { Output, Options, ResultCallback } from "../types";
-import { Walker } from "./walker";
+import type { Output, Options, ResultCallback } from "../types.ts";
+import { Walker } from "./walker.ts";
 
 export function promise<TOutput extends Output>(
   root: string,
diff --git a/src/api/functions/get-array.ts b/src/api/functions/get-array.ts
index c870b6a3..6f3d3263 100644
--- a/src/api/functions/get-array.ts
+++ b/src/api/functions/get-array.ts
@@ -1,4 +1,4 @@
-import { Options } from "../../types";
+import type { Options } from "../../types.ts";
 
 export type GetArrayFunction = (paths: string[]) => string[];
 
diff --git a/src/api/functions/group-files.ts b/src/api/functions/group-files.ts
index f53a04b3..e498258f 100644
--- a/src/api/functions/group-files.ts
+++ b/src/api/functions/group-files.ts
@@ -1,4 +1,4 @@
-import { Group, Options } from "../../types";
+import type { Group, Options } from "../../types.ts";
 
 export type GroupFilesFunction = (
   groups: Group[],
diff --git a/src/api/functions/invoke-callback.ts b/src/api/functions/invoke-callback.ts
index 9dd66a0c..77f54777 100644
--- a/src/api/functions/invoke-callback.ts
+++ b/src/api/functions/invoke-callback.ts
@@ -1,4 +1,4 @@
-import {
+import type {
   Output,
   PathsOutput,
   OnlyCountsOutput,
@@ -6,7 +6,7 @@ import {
   ResultCallback,
   WalkerState,
   Options,
-} from "../../types";
+} from "../../types.ts";
 
 export type InvokeCallbackFunction<TOutput extends Output> = (
   state: WalkerState,
diff --git a/src/api/functions/join-path.ts b/src/api/functions/join-path.ts
index d103cb2c..2870a0f8 100644
--- a/src/api/functions/join-path.ts
+++ b/src/api/functions/join-path.ts
@@ -1,6 +1,6 @@
 import { relative } from "path";
-import { Options, PathSeparator } from "../../types";
-import { convertSlashes } from "../../utils";
+import type { Options, PathSeparator } from "../../types.ts";
+import { convertSlashes } from "../../utils.ts";
 
 export function joinPathWithBasePath(filename: string, directoryPath: string) {
   return directoryPath + filename;
diff --git a/src/api/functions/push-directory.ts b/src/api/functions/push-directory.ts
index 2de954b8..0f0f868b 100644
--- a/src/api/functions/push-directory.ts
+++ b/src/api/functions/push-directory.ts
@@ -1,4 +1,4 @@
-import { FilterPredicate, Options } from "../../types";
+import type { FilterPredicate, Options } from "../../types.ts";
 
 export type PushDirectoryFunction = (
   directoryPath: string,
diff --git a/src/api/functions/push-file.ts b/src/api/functions/push-file.ts
index 18ef77dc..9f3ac58f 100644
--- a/src/api/functions/push-file.ts
+++ b/src/api/functions/push-file.ts
@@ -1,4 +1,4 @@
-import { FilterPredicate, Options, Counts } from "../../types";
+import type { FilterPredicate, Options, Counts } from "../../types.ts";
 
 export type PushFileFunction = (
   directoryPath: string,
diff --git a/src/api/functions/resolve-symlink.ts b/src/api/functions/resolve-symlink.ts
index b23cdb2b..92fa34ff 100644
--- a/src/api/functions/resolve-symlink.ts
+++ b/src/api/functions/resolve-symlink.ts
@@ -1,6 +1,6 @@
 import type { Stats } from "fs";
-import { WalkerState, Options } from "../../types";
 import { dirname } from "path";
+import type { WalkerState, Options } from "../../types.ts";
 
 export type ResolveSymlinkFunction = (
   path: string,
diff --git a/src/api/functions/walk-directory.ts b/src/api/functions/walk-directory.ts
index f2b9d368..428dcd71 100644
--- a/src/api/functions/walk-directory.ts
+++ b/src/api/functions/walk-directory.ts
@@ -1,5 +1,5 @@
-import { WalkerState } from "../../types";
 import type { Dirent } from "fs";
+import type { WalkerState } from "../../types.ts";
 
 export type WalkDirectoryFunction = (
   state: WalkerState,
diff --git a/src/api/queue.ts b/src/api/queue.ts
index dfb491ff..f91a8a99 100644
--- a/src/api/queue.ts
+++ b/src/api/queue.ts
@@ -1,4 +1,4 @@
-import { WalkerState } from "../types";
+import type { WalkerState } from "../types.ts";
 
 type OnQueueEmptyCallback = (error: Error | null, output: WalkerState) => void;
 /**
@@ -8,7 +8,11 @@ type OnQueueEmptyCallback = (error: Error | null, output: WalkerState) => void;
  */
 export class Queue {
   count: number = 0;
-  constructor(private onQueueEmpty?: OnQueueEmptyCallback) {}
+  private onQueueEmpty?: OnQueueEmptyCallback;
+
+  constructor(onQueueEmpty?: OnQueueEmptyCallback) {
+    this.onQueueEmpty = onQueueEmpty;
+  }
 
   enqueue() {
     this.count++;
diff --git a/src/api/sync.ts b/src/api/sync.ts
index 02a3ea67..6aab2caf 100644
--- a/src/api/sync.ts
+++ b/src/api/sync.ts
@@ -1,5 +1,5 @@
-import { Output, Options } from "../types";
-import { Walker } from "./walker";
+import type { Output, Options } from "../types.ts";
+import { Walker } from "./walker.ts";
 
 export function sync<TOutput extends Output>(
   root: string,
diff --git a/src/api/walker.ts b/src/api/walker.ts
index e6edc0dc..1777edca 100644
--- a/src/api/walker.ts
+++ b/src/api/walker.ts
@@ -1,20 +1,19 @@
 import { basename, dirname } from "path";
-import { isRootDirectory, normalizePath } from "../utils";
-import { ResultCallback, WalkerState, Options } from "../types";
-import * as joinPath from "./functions/join-path";
-import * as pushDirectory from "./functions/push-directory";
-import * as pushFile from "./functions/push-file";
-import * as getArray from "./functions/get-array";
-import * as groupFiles from "./functions/group-files";
-import * as resolveSymlink from "./functions/resolve-symlink";
-import * as invokeCallback from "./functions/invoke-callback";
-import * as walkDirectory from "./functions/walk-directory";
-import { Queue } from "./queue";
-import type { Dirent } from "fs";
-import * as nativeFs from "fs";
-import { Output } from "../types";
-import { Counter } from "./counter";
-import { Aborter } from "./aborter";
+import nativeFs, { type Dirent } from "fs";
+import { isRootDirectory, normalizePath } from "../utils.ts";
+import type { ResultCallback, WalkerState, Options } from "../types.ts";
+import * as joinPath from "./functions/join-path.ts";
+import * as pushDirectory from "./functions/push-directory.ts";
+import * as pushFile from "./functions/push-file.ts";
+import * as getArray from "./functions/get-array.ts";
+import * as groupFiles from "./functions/group-files.ts";
+import * as resolveSymlink from "./functions/resolve-symlink.ts";
+import * as invokeCallback from "./functions/invoke-callback.ts";
+import * as walkDirectory from "./functions/walk-directory.ts";
+import { Queue } from "./queue.ts";
+import type { Output } from "../types.ts";
+import { Counter } from "./counter.ts";
+import { Aborter } from "./aborter.ts";
 
 export class Walker<TOutput extends Output> {
   private readonly root: string;
diff --git a/src/builder/api-builder.ts b/src/builder/api-builder.ts
index 4c1af175..c2972b38 100644
--- a/src/builder/api-builder.ts
+++ b/src/builder/api-builder.ts
@@ -1,12 +1,15 @@
-import { callback, promise } from "../api/async";
-import { sync } from "../api/sync";
-import { Options, Output, ResultCallback } from "../types";
+import { callback, promise } from "../api/async.ts";
+import { sync } from "../api/sync.ts";
+import type { Options, Output, ResultCallback } from "../types.ts";
 
 export class APIBuilder<TReturnType extends Output> {
-  constructor(
-    private readonly root: string,
-    private readonly options: Options
-  ) {}
+  private readonly root: string;
+  private readonly options: Options;
+
+  constructor(root: string, options: Options) {
+    this.root = root;
+    this.options = options;
+  }
 
   withPromise(): Promise<TReturnType> {
     return promise(this.root, this.options);
diff --git a/src/builder/index.ts b/src/builder/index.ts
index a0fc4be8..12960585 100644
--- a/src/builder/index.ts
+++ b/src/builder/index.ts
@@ -1,5 +1,5 @@
 import { sep } from "path";
-import {
+import type {
   Output,
   OnlyCountsOutput,
   GroupOutput,
@@ -10,8 +10,8 @@ import {
   GlobFunction,
   GlobMatcher,
   GlobParams,
-} from "../types";
-import { APIBuilder } from "./api-builder";
+} from "../types.ts";
+import { APIBuilder } from "./api-builder.ts";
 import type picomatch from "picomatch";
 
 let pm: typeof picomatch | null = null;
diff --git a/src/index.ts b/src/index.ts
index fba8ef8b..28b037d3 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -1,6 +1,6 @@
-import { Builder } from "./builder";
+import { Builder } from "./builder/index.ts";
 
 export { Builder as fdir };
 export type Fdir = typeof Builder;
 
-export * from "./types";
+export * from "./types.ts";
diff --git a/src/types.ts b/src/types.ts
index da900e01..10d257fa 100644
--- a/src/types.ts
+++ b/src/types.ts
@@ -1,6 +1,6 @@
-import { Aborter } from "./api/aborter";
-import { Queue } from "./api/queue";
-import type * as nativeFs from "fs";
+import type fs from 'fs';
+import { Aborter } from "./api/aborter.ts";
+import { Queue } from "./api/queue.ts";
 
 export type Counts = {
   files: number;
@@ -28,12 +28,12 @@ export type PathsOutput = string[];
 export type Output = OnlyCountsOutput | PathsOutput | GroupOutput;
 
 export type FSLike = {
-  readdir: typeof nativeFs.readdir;
-  readdirSync: typeof nativeFs.readdirSync;
-  realpath: typeof nativeFs.realpath;
-  realpathSync: typeof nativeFs.realpathSync;
-  stat: typeof nativeFs.stat;
-  statSync: typeof nativeFs.statSync;
+  readdir: typeof fs.readdir;
+  readdirSync: typeof fs.readdirSync;
+  realpath: typeof fs.realpath;
+  realpathSync: typeof fs.realpathSync;
+  stat: typeof fs.stat;
+  statSync: typeof fs.statSync;
 };
 
 export type WalkerState = {
diff --git a/src/utils.ts b/src/utils.ts
index 66260cf8..2b2490b7 100644
--- a/src/utils.ts
+++ b/src/utils.ts
@@ -1,5 +1,5 @@
 import { sep, normalize, resolve } from "path";
-import { PathSeparator } from "./types";
+import type { PathSeparator } from "./types.ts";
 
 export function cleanPath(path: string) {
   let normalized = normalize(path);
diff --git a/tsconfig.json b/tsconfig.json
index e285fa9b..7128bb85 100644
--- a/tsconfig.json
+++ b/tsconfig.json
@@ -1,13 +1,15 @@
 {
   "compilerOptions": {
-    "target": "ESNext",
-    "module": "CommonJS",
-    "moduleResolution": "node",
+    "target": "esnext",
+    "module": "node16",
     "lib": ["esnext"],
     "declaration": true,
     "outDir": "./dist",
+    "noEmit": true,
     "esModuleInterop": true,
-    "forceConsistentCasingInFileNames": true,
+    "erasableSyntaxOnly": true,
+    "allowImportingTsExtensions": true,
+    "verbatimModuleSyntax": true,
     "strict": true,
     "skipLibCheck": true,
     "resolveJsonModule": true,