diff --git a/demo/browser.js b/demo/browser.js
index 9092b2c4..78b1d690 100644
--- a/demo/browser.js
+++ b/demo/browser.js
@@ -4,6 +4,8 @@ import Menu from './menu.js';
 
 const human = new Human();
 
+const userConfig = {}; // add any user configuration overrides
+
 // ui options
 const ui = {
   baseColor: 'rgba(173, 216, 230, 0.3)', // 'lightblue' with light alpha channel
@@ -220,9 +222,9 @@ function runHumanDetect(input, canvas) {
     ctx.drawImage(input, 0, 0, input.width, input.height, 0, 0, canvas.width, canvas.height);
     const data = ctx.getImageData(0, 0, canvas.width, canvas.height);
     // perform detection in worker
-    webWorker(input, data, canvas);
+    webWorker(input, data, canvas, userConfig);
   } else {
-    human.detect(input).then((result) => {
+    human.detect(input, userConfig).then((result) => {
       if (result.error) log(result.error);
       else drawResults(input, result, canvas);
     });
@@ -241,7 +243,7 @@ async function processImage(input) {
       image.height = image.naturalHeight;
       canvas.width = human.config.filter.width && human.config.filter.width > 0 ? human.config.filter.width : image.naturalWidth;
       canvas.height = human.config.filter.height && human.config.filter.height > 0 ? human.config.filter.height : image.naturalHeight;
-      const result = await human.detect(image);
+      const result = await human.detect(image, userConfig);
       drawResults(image, result, canvas);
       const thumb = document.createElement('canvas');
       thumb.className = 'thumbnail';
@@ -383,15 +385,16 @@ async function main() {
   log('Human: demo starting ...');
   setupMenu();
   document.getElementById('log').innerText = `Human: version ${human.version} TensorFlow/JS: version ${human.tf.version_core}`;
-  // this is not required, just pre-warms the library
+  // this is not required, just pre-loads all models
   if (ui.modelsPreload) {
     status('loading');
-    await human.load();
+    await human.load(userConfig);
   }
+  // this is not required, just pre-warms all models for faster initial inference
   if (ui.modelsWarmup) {
     status('initializing');
-    const warmup = new ImageData(50, 50);
-    await human.detect(warmup);
+    const warmup = new ImageData(256, 256);
+    await human.detect(warmup, userConfig);
   }
   status('human: ready');
   document.getElementById('loader').style.display = 'none';
diff --git a/demo/index.html b/demo/index.html
index 28698af2..b45f2bf5 100644
--- a/demo/index.html
+++ b/demo/index.html
@@ -15,7 +15,7 @@
   <link rel="apple-touch-icon" href="../assets/icon.png">
     <!-- not required for tfjs cpu or webgl backends, required if you want to use tfjs wasm or webgpu backends -->
     <!-- <script src="https://cdn.jsdelivr.net/npm/@tensorflow/tfjs@2.7.0/dist/tf.es2017.js"></script> -->
-    <!-- <script src="https://cdn.jsdelivr.net/npm/@tensorflow/tfjs-backend-wasm@2.7.0/dist/tf-backend-wasm.js"></script> -->
+    <!-- <script src="https://cdn.jsdelivr.net/npm/@tensorflow/tfjs-backend-wasm@2.7.0/dist/tf-backend-wasm.es2017.js"></script> -->
     <!-- <script src="https://cdn.jsdelivr.net/npm/@tensorflow/tfjs-backend-webgpu@0.0.1-alpha.0/dist/tf-webgpu.js"></script> -->
     <!-- load compiled demo js -->
     <script src="../dist/demo-browser-index.js"></script>
diff --git a/demo/worker.js b/demo/worker.js
index e796631e..8b62675d 100644
--- a/demo/worker.js
+++ b/demo/worker.js
@@ -16,7 +16,7 @@ onmessage = async (msg) => {
   const image = new ImageData(new Uint8ClampedArray(msg.data.image), msg.data.width, msg.data.height);
   let result = {};
   try {
-    result = await human.detect(image);
+    result = await human.detect(image, msg.data.userConfig);
   } catch (err) {
     result.error = err.message;
     log('worker thread error:', err.message);
diff --git a/src/human.js b/src/human.js
index b23fa91d..0a306bee 100644
--- a/src/human.js
+++ b/src/human.js
@@ -42,10 +42,10 @@ function mergeDeep(...objects) {
 }
 
 class Human {
-  constructor() {
+  constructor(userConfig = {}) {
     this.tf = tf;
     this.version = app.version;
-    this.config = defaults;
+    this.config = mergeDeep(defaults, userConfig);
     this.fx = null;
     this.state = 'idle';
     this.numTensors = 0;
@@ -152,7 +152,7 @@ class Human {
   // check if backend needs initialization if it changed
   async checkBackend(force) {
     const timeStamp = now();
-    if (force || (tf.getBackend() !== this.config.backend)) {
+    if (this.config.backend && (this.config.backend !== '') && force || (tf.getBackend() !== this.config.backend)) {
       this.state = 'backend';
       /* force backend reload
       if (this.config.backend in tf.engine().registry) {
@@ -167,16 +167,16 @@ class Human {
       await tf.setBackend(this.config.backend);
       tf.enableProdMode();
       /* debug mode is really too mcuh
-      if (this.config.profile) tf.enableDebugMode();
-      else tf.enableProdMode();
+      tf.enableDebugMode();
       */
-      if (this.config.deallocate && this.config.backend === 'webgl') {
-        this.log('Changing WebGL: WEBGL_DELETE_TEXTURE_THRESHOLD:', this.config.deallocate);
-        tf.ENV.set('WEBGL_DELETE_TEXTURE_THRESHOLD', this.config.deallocate ? 0 : -1);
+      if (this.config.backend === 'webgl') {
+        if (this.config.deallocate) {
+          this.log('Changing WebGL: WEBGL_DELETE_TEXTURE_THRESHOLD:', this.config.deallocate);
+          tf.ENV.set('WEBGL_DELETE_TEXTURE_THRESHOLD', this.config.deallocate ? 0 : -1);
+        }
+        // tf.ENV.set('WEBGL_FORCE_F16_TEXTURES', true);
+        tf.ENV.set('WEBGL_PACK_DEPTHWISECONV', true);
       }
-      // tf.ENV.set('WEBGL_CPU_FORWARD', true);
-      // tf.ENV.set('WEBGL_FORCE_F16_TEXTURES', true);
-      tf.ENV.set('WEBGL_PACK_DEPTHWISECONV', true);
       await tf.ready();
     }
     const current = Math.trunc(now() - timeStamp);