diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 26ab6b2..44e4908 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -9,6 +9,6 @@ jobs:
     steps:
       - uses: actions/checkout@v3
       - run: npm i
-      - run: npm run build
       - run: npm run lint
+      - run: npm run typecheck
       - run: npm test
diff --git a/index.html b/index.html
index 6cce46d..a056667 100644
--- a/index.html
+++ b/index.html
@@ -31,7 +31,7 @@
   <body>
     <div id="dropzone">Drop .parquet file here</div>
     <script type="module">
-      import { parquetMetadata, toJson } from './dist/metadata.js'
+      import { parquetMetadata, toJson } from './src/metadata.js'
 
       const dropZone = document.getElementById('dropzone')
 
diff --git a/package.json b/package.json
index b457a72..95e7d1b 100644
--- a/package.json
+++ b/package.json
@@ -11,18 +11,18 @@
     "type": "git",
     "url": "https://github.com/hyparam/hyparquet"
   },
-  "main": "dist/hyparquet.js",
+  "main": "src/hyparquet.js",
   "files": [
-    "dist"
+    "src"
   ],
   "type": "module",
-  "types": "dist/hyparquet.d.ts",
+  "types": "src/hyparquet.d.ts",
   "scripts": {
-    "build": "tsc && cp src/*.js dist",
     "coverage": "vitest run --coverage",
     "demo": "http-server -o",
-    "lint": "eslint . --ext .ts,.js",
-    "test": "vitest run"
+    "lint": "eslint .",
+    "test": "vitest run",
+    "typecheck": "tsc"
   },
   "devDependencies": {
     "@types/node": "20.10.6",
diff --git a/src/hyparquet.d.ts b/src/hyparquet.d.ts
new file mode 100644
index 0000000..c258bfd
--- /dev/null
+++ b/src/hyparquet.d.ts
@@ -0,0 +1,17 @@
+/**
+ * Read parquet data rows from a file
+ *
+ * @param {ArrayBuffer} arrayBuffer parquet file contents
+ * @returns {any[][]} row data
+ */
+export function parquetRead(arrayBuffer: ArrayBuffer): any[][]
+
+
+/**
+ * Read parquet header, metadata, and schema information from a file
+ *
+ * @typedef {import("./hyparquet.js").FileMetaData} FileMetaData
+ * @param {ArrayBuffer} arrayBuffer parquet file contents
+ * @returns {FileMetaData} metadata object
+ */
+export function parquetMetadata(arrayBuffer: ArrayBuffer): any
diff --git a/src/hyparquet.ts b/src/hyparquet.js
similarity index 79%
rename from src/hyparquet.ts
rename to src/hyparquet.js
index a37c13a..a11437f 100644
--- a/src/hyparquet.ts
+++ b/src/hyparquet.js
@@ -1,4 +1,5 @@
 import { parquetMetadata } from './metadata.js'
+export { parquetMetadata }
 
 /**
  * Read parquet data rows from a file
@@ -6,7 +7,7 @@ import { parquetMetadata } from './metadata.js'
  * @param {ArrayBuffer} arrayBuffer parquet file contents
  * @returns {any[][]} row data
  */
-export function parquetRead(arrayBuffer: ArrayBuffer): any[][] {
+export function parquetRead(arrayBuffer) {
   const metadata = parquetMetadata(arrayBuffer)
   throw new Error('not implemented')
 }
diff --git a/src/metadata.js b/src/metadata.js
index ae20795..6ce66c5 100644
--- a/src/metadata.js
+++ b/src/metadata.js
@@ -3,7 +3,7 @@ import { deserializeTCompactProtocol } from './thrift.js'
 /**
  * Read parquet header, metadata, and schema information from a file
  *
- * @typedef {import("./types.js").FileMetaData} FileMetaData
+ * @typedef {import("./types.d.ts").FileMetaData} FileMetaData
  * @param {ArrayBuffer} arrayBuffer parquet file contents
  * @returns {FileMetaData} metadata object
  */
diff --git a/src/thrift.js b/src/thrift.js
index c5c4b32..78ec048 100644
--- a/src/thrift.js
+++ b/src/thrift.js
@@ -19,7 +19,7 @@ const CompactType = {
 /**
  * Parse TCompactProtocol
  *
- * @typedef {import("./types.js").Decoded<T>} Decoded
+ * @typedef {import("./types.d.ts").Decoded<T>} Decoded
  * @template T
  * @param {ArrayBuffer} arrayBuffer
  * @returns {Decoded<Record<string, any>>}
diff --git a/test/metadata.test.js b/test/metadata.test.js
index db8847e..ff523f6 100644
--- a/test/metadata.test.js
+++ b/test/metadata.test.js
@@ -1,6 +1,6 @@
 import { promises as fs } from 'fs'
 import { describe, expect, it } from 'vitest'
-import { parquetMetadata, toJson } from '../src/metadata'
+import { parquetMetadata, toJson } from '../src/metadata.js'
 
 /**
  * Helper function to read .parquet file into ArrayBuffer
diff --git a/test/snappy.test.js b/test/snappy.test.js
index 86c72e6..fb91ad6 100644
--- a/test/snappy.test.js
+++ b/test/snappy.test.js
@@ -1,5 +1,5 @@
 import { describe, expect, it } from 'vitest'
-import { snappyUncompress } from '../src/snappy'
+import { snappyUncompress } from '../src/snappy.js'
 
 describe('snappy uncompress', () => {
   it('decompresses valid input correctly', () => {
diff --git a/test/thrift.test.js b/test/thrift.test.js
index ec51136..05046cc 100644
--- a/test/thrift.test.js
+++ b/test/thrift.test.js
@@ -1,5 +1,5 @@
 import { describe, expect, it } from 'vitest'
-import { deserializeTCompactProtocol, toVarInt } from '../src/thrift'
+import { deserializeTCompactProtocol, toVarInt } from '../src/thrift.js'
 
 describe('deserializeTCompactProtocol function', () => {
 
diff --git a/tsconfig.json b/tsconfig.json
index 36a613c..6465dd1 100644
--- a/tsconfig.json
+++ b/tsconfig.json
@@ -4,11 +4,11 @@
     "checkJs": true,
     "lib": ["esnext", "dom"],
     "module": "nodenext",
-    "outDir": "dist",
+    "noEmit": true,
+    "resolveJsonModule": true,
     "skipLibCheck": true,
-    "sourceMap": true,
     "strict": true,
     "target": "esnext",
   },
-  "include": ["src"]
+  "include": ["src", "test"]
 }
