diff --git a/modules/ecash-lib/src/ecc.test.ts b/modules/ecash-lib/src/ecc.test.ts
--- a/modules/ecash-lib/src/ecc.test.ts
+++ b/modules/ecash-lib/src/ecc.test.ts
@@ -3,14 +3,14 @@
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
 import { expect } from 'chai';
-import fs from 'node:fs/promises';
 
 import { fromHex, toHex } from './io/hex.js';
-import { EccDummy, EccWasm, initWasm } from './ecc.js';
+import { EccDummy, EccWasm } from './ecc.js';
+import { initWasm } from './init.js';
 
 describe('Ecc', async () => {
     // Can't use `fetch` for local file so we have to read it using `fs`
-    await initWasm(fs.readFile('./src/ffi/ecash_lib_wasm_bg.wasm'));
+    await initWasm();
 
     it('EccWasm', () => {
         const ecc = new EccWasm();
diff --git a/modules/ecash-lib/src/ecc.ts b/modules/ecash-lib/src/ecc.ts
--- a/modules/ecash-lib/src/ecc.ts
+++ b/modules/ecash-lib/src/ecc.ts
@@ -5,7 +5,6 @@
 // These files are generated in "ecash-lib-wasm" via build-wasm.sh or
 // dockerbuild.sh.
 import * as ffi from './ffi/ecash_lib_wasm.js';
-import __wbg_init from './ffi/ecash_lib_wasm.js';
 
 /** Interface to abstract over Elliptic Curve Cryptography */
 export interface Ecc {
@@ -21,8 +20,6 @@
 
 /** Ecc implementation using WebAssembly */
 export const EccWasm = ffi.Ecc;
-/** Download and initialize the WASM module, or use the provided buffer */
-export const initWasm = __wbg_init;
 
 /** Dummy Ecc impl that always returns 0, useful for measuring tx size */
 export class EccDummy implements Ecc {
diff --git a/modules/ecash-lib/src/hash.test.ts b/modules/ecash-lib/src/hash.test.ts
--- a/modules/ecash-lib/src/hash.test.ts
+++ b/modules/ecash-lib/src/hash.test.ts
@@ -3,10 +3,9 @@
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
 import { expect } from 'chai';
-import fs from 'node:fs/promises';
 
 import { fromHex, toHex, toHexRev } from './io/hex.js';
-import { initWasm } from './ecc.js';
+import { initWasm } from './init.js';
 import { sha256, sha256d, shaRmd160 } from './hash.js';
 
 const GENESIS_HEADER_HEX =
@@ -17,7 +16,7 @@
 
 describe('Ecc', async () => {
     // Can't use `fetch` for local file so we have to read it using `fs`
-    await initWasm(fs.readFile('./src/ffi/ecash_lib_wasm_bg.wasm'));
+    await initWasm();
 
     it('sha256', () => {
         expect(toHex(sha256(new Uint8Array()))).to.equal(
diff --git a/modules/ecash-lib/src/index.ts b/modules/ecash-lib/src/index.ts
--- a/modules/ecash-lib/src/index.ts
+++ b/modules/ecash-lib/src/index.ts
@@ -4,6 +4,7 @@
 
 export * from './ecc.js';
 export * from './hash.js';
+export * from './init.js';
 export * from './op.js';
 export * from './opcode.js';
 export * from './script.js';
diff --git a/modules/ecash-lib/src/init.ts b/modules/ecash-lib/src/init.ts
new file mode 100644
--- /dev/null
+++ b/modules/ecash-lib/src/init.ts
@@ -0,0 +1,18 @@
+// Copyright (c) 2024 The Bitcoin developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+import __wbg_init from './ffi/ecash_lib_wasm.js';
+
+/** Load and initialize the WASM module */
+export async function initWasm() {
+    if (typeof window === 'undefined') {
+        // On Node, read the file off the disk
+        const fs = await import('node:fs/promises');
+        const wasmUrl = new URL('ffi/ecash_lib_wasm_bg.wasm', import.meta.url);
+        return await __wbg_init(fs.readFile(wasmUrl));
+    } else {
+        // Browser, use default, will use fetch internally
+        return await __wbg_init();
+    }
+}
diff --git a/modules/ecash-lib/src/unsignedTx.test.ts b/modules/ecash-lib/src/unsignedTx.test.ts
--- a/modules/ecash-lib/src/unsignedTx.test.ts
+++ b/modules/ecash-lib/src/unsignedTx.test.ts
@@ -3,7 +3,6 @@
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
 import { expect } from 'chai';
-import fs from 'node:fs/promises';
 
 import { fromHex, toHex } from './io/hex.js';
 import { Script } from './script.js';
@@ -19,7 +18,7 @@
     SINGLE_ANYONECANPAY_BIP143,
     SINGLE_BIP143,
 } from './sigHashType.js';
-import { initWasm } from './ecc.js';
+import { initWasm } from './init.js';
 
 const TX = new Tx({
     version: 0xfacefeed,
@@ -88,7 +87,7 @@
 
 describe('UnsignedTx', async () => {
     // Can't use `fetch` for local file so we have to read it using `fs`
-    await initWasm(fs.readFile('./src/ffi/ecash_lib_wasm_bg.wasm'));
+    await initWasm();
 
     it('UnsignedTx.dummyFromTx', () => {
         const dummy = UnsignedTx.dummyFromTx(new Tx());
diff --git a/modules/ecash-lib/tests/alp.test.ts b/modules/ecash-lib/tests/alp.test.ts
--- a/modules/ecash-lib/tests/alp.test.ts
+++ b/modules/ecash-lib/tests/alp.test.ts
@@ -5,7 +5,6 @@
 import { expect, use } from 'chai';
 import { ChildProcess, spawn } from 'node:child_process';
 import { EventEmitter, once } from 'node:events';
-import fs from 'node:fs/promises';
 
 import { ChronikClientNode } from 'chronik-client';
 
@@ -144,7 +143,7 @@
         });
 
         // Can't use `fetch` for local file so we have to read it using `fs`
-        await initWasm(fs.readFile('./src/ffi/ecash_lib_wasm_bg.wasm'));
+        await initWasm();
         ecc = new EccWasm();
 
         // We got the coins, can fan out now
diff --git a/modules/ecash-lib/tests/txBuilder.test.ts b/modules/ecash-lib/tests/txBuilder.test.ts
--- a/modules/ecash-lib/tests/txBuilder.test.ts
+++ b/modules/ecash-lib/tests/txBuilder.test.ts
@@ -5,7 +5,6 @@
 import { expect, use } from 'chai';
 import { ChildProcess, spawn } from 'node:child_process';
 import { EventEmitter, once } from 'node:events';
-import fs from 'node:fs/promises';
 
 import { ChronikClientNode } from 'chronik-client';
 
@@ -155,7 +154,7 @@
         });
 
         // Can't use `fetch` for local file so we have to read it using `fs`
-        await initWasm(fs.readFile('./src/ffi/ecash_lib_wasm_bg.wasm'));
+        await initWasm();
         ecc = new EccWasm();
 
         // We got the coins, can fan out now