diff --git a/.github/workflows/publish_docs.yml b/.github/workflows/publish_docs.yml
index 54171575..80bb6c23 100644
--- a/.github/workflows/publish_docs.yml
+++ b/.github/workflows/publish_docs.yml
@@ -22,6 +22,14 @@ jobs:
           python -m pip install --upgrade pip
           pip install requests pandas markdown pytablereader tabulate
           npm install
+      - name: Set up Emscripten
+        uses: mymindstorm/setup-emsdk@v14
+        with:
+          version: 3.1.61
+          actions-cache-folder: emsdk-cache
+      - name: Build browser WebAssembly decoder
+        run: npm run build:web
+        working-directory: nodejs/theengs-decoder
       - name: Build documentation
         run: |
           npm run docs:build
diff --git a/.gitignore b/.gitignore
index e5db5b23..e1bec7ce 100644
--- a/.gitignore
+++ b/.gitignore
@@ -14,6 +14,8 @@ docs/.vitepress/dist/
 docs/.vitepress/cache/
 docs/.vitepress/public/commonConfig.js
 docs/.vitepress/public/img/
+docs/.vitepress/public/wasm/
 docs/.vitepress/data/devices.json
+nodejs/theengs-decoder/build-web/
 docs/devices/_app_devices.md
 generated/
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 2dca9968..1946ae4c 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -41,6 +41,27 @@ elseif(BUILD_WASM)
         LINK_FLAGS "-lembind -sMODULARIZE=1 -sEXPORT_NAME=createTheengsDecoderModule -sENVIRONMENT=node -sALLOW_MEMORY_GROWTH=1 -sSINGLE_FILE=1 -sNODEJS_CATCH_EXIT=0 -sNODEJS_CATCH_REJECTION=0"
     )
 
+elseif(BUILD_WASM_WEB)
+    message(STATUS "Building WebAssembly module via Emscripten (browser target)")
+
+    add_executable(theengs_decoder_web
+        nodejs/theengs-decoder/src/wasm_bindings.cc
+        src/decoder.cpp
+    )
+
+    target_include_directories(theengs_decoder_web
+        PRIVATE
+            ${CMAKE_CURRENT_SOURCE_DIR}/src/arduino_json/src
+            ${CMAKE_CURRENT_SOURCE_DIR}/src
+    )
+
+    target_compile_features(theengs_decoder_web PRIVATE cxx_std_17)
+
+    set_target_properties(theengs_decoder_web PROPERTIES
+        SUFFIX ".js"
+        LINK_FLAGS "-lembind -sMODULARIZE=1 -sEXPORT_ES6=1 -sEXPORT_NAME=createTheengsDecoderModule -sENVIRONMENT=web,worker -sALLOW_MEMORY_GROWTH=1 -sSINGLE_FILE=1"
+    )
+
 else()
 
     add_library(decoder
diff --git a/docs/.vitepress/components/WebParser.vue b/docs/.vitepress/components/WebParser.vue
new file mode 100644
index 00000000..5c779f76
--- /dev/null
+++ b/docs/.vitepress/components/WebParser.vue
@@ -0,0 +1,311 @@
+<script setup lang="ts">
+import { computed, onMounted, ref, shallowRef } from 'vue'
+
+const DEFAULT_PAYLOAD = {
+  id: '88:22:44:44:11:44',
+  rssi: -85,
+  servicedata: '08094411444422880104e500c6020702aa2702012d',
+  servicedatauuid: '0xfdcd',
+}
+
+const input = ref(JSON.stringify(DEFAULT_PAYLOAD, null, 2))
+const status = ref<'idle' | 'loading' | 'ready' | 'error'>('idle')
+const errorMsg = ref<string | null>(null)
+const result = ref<unknown>(null)
+const noMatch = ref(false)
+const decoder = shallowRef<any>(null)
+
+const formattedResult = computed(() =>
+  result.value === null ? '' : JSON.stringify(result.value, null, 2),
+)
+
+async function loadDecoder() {
+  if (decoder.value || status.value === 'loading') return
+  status.value = 'loading'
+  try {
+    const base = (import.meta as any).env?.BASE_URL ?? '/'
+    const path = `${base}wasm/theengs_decoder_web.js`
+    const absoluteUrl = new URL(path, window.location.href).href
+    const shimSource = `export { default } from ${JSON.stringify(absoluteUrl)}`
+    const blob = new Blob([shimSource], { type: 'application/javascript' })
+    const blobUrl = URL.createObjectURL(blob)
+    let mod: any
+    try {
+      mod = await import(/* @vite-ignore */ blobUrl)
+    } finally {
+      URL.revokeObjectURL(blobUrl)
+    }
+    const factory = mod.default ?? mod.createTheengsDecoderModule
+    const Module = await factory()
+    decoder.value = new Module.TheengsDecoder()
+    status.value = 'ready'
+  } catch (err: any) {
+    status.value = 'error'
+    errorMsg.value = `Failed to load decoder: ${err?.message ?? err}`
+  }
+}
+
+function decode() {
+  errorMsg.value = null
+  noMatch.value = false
+  result.value = null
+
+  if (!decoder.value) {
+    errorMsg.value = 'Decoder not ready yet. Try again in a moment.'
+    return
+  }
+
+  let parsed: Record<string, unknown>
+  try {
+    parsed = JSON.parse(input.value)
+  } catch (err: any) {
+    errorMsg.value = `Invalid JSON: ${err?.message ?? err}`
+    return
+  }
+
+  if (!parsed || typeof parsed !== 'object' || Array.isArray(parsed)) {
+    errorMsg.value = 'Input must be a JSON object.'
+    return
+  }
+
+  if (!('servicedata' in parsed) && !('manufacturerdata' in parsed)) {
+    errorMsg.value =
+      'Object must include at least one of "servicedata" or "manufacturerdata".'
+    return
+  }
+
+  try {
+    const raw = decoder.value.decodeBLE(JSON.stringify(parsed))
+    if (!raw) {
+      noMatch.value = true
+      return
+    }
+    result.value = JSON.parse(raw)
+  } catch (err: any) {
+    errorMsg.value = `Decode failed: ${err?.message ?? err}`
+  }
+}
+
+function resetExample() {
+  input.value = JSON.stringify(DEFAULT_PAYLOAD, null, 2)
+  errorMsg.value = null
+  noMatch.value = false
+  result.value = null
+}
+
+onMounted(() => {
+  loadDecoder()
+})
+</script>
+
+<template>
+  <div class="web-parser">
+    <p class="intro">
+      Paste a BLE advertisement as a JSON object below and the decoder runs
+      locally in your browser via WebAssembly — no data leaves your device.
+      The object must include
+      <code>servicedata</code> or <code>manufacturerdata</code> (hex strings),
+      optionally with <code>servicedatauuid</code>, <code>name</code>,
+      <code>mac</code>, or <code>id</code>.
+    </p>
+
+    <div class="controls">
+      <button type="button" class="reset-btn" @click="resetExample">
+        Reset to example
+      </button>
+      <span class="status" :data-state="status">
+        <template v-if="status === 'loading'">Loading decoder…</template>
+        <template v-else-if="status === 'ready'">Decoder ready</template>
+        <template v-else-if="status === 'error'">Decoder unavailable</template>
+        <template v-else>Initializing…</template>
+      </span>
+    </div>
+
+    <div class="grid">
+      <div class="pane">
+        <label class="pane-label" for="parser-input">Input JSON</label>
+        <textarea
+          id="parser-input"
+          v-model="input"
+          spellcheck="false"
+          autocomplete="off"
+          autocapitalize="off"
+          rows="10"
+        />
+        <button
+          class="decode-btn"
+          :disabled="status !== 'ready'"
+          @click="decode"
+        >
+          Decode
+        </button>
+      </div>
+
+      <div class="pane">
+        <label class="pane-label">Decoded output</label>
+        <pre v-if="errorMsg" class="output error">{{ errorMsg }}</pre>
+        <pre v-else-if="noMatch" class="output muted">No decoder matched this payload.</pre>
+        <pre v-else-if="formattedResult" class="output">{{ formattedResult }}</pre>
+        <pre v-else class="output muted">Click <strong>Decode</strong> to see the result.</pre>
+      </div>
+    </div>
+  </div>
+</template>
+
+<style scoped>
+.web-parser {
+  margin: 1rem 0 2rem;
+}
+
+.intro {
+  color: var(--vp-c-text-2);
+  font-size: 0.95rem;
+  line-height: 1.55;
+  margin-bottom: 1.25rem;
+}
+
+.intro code {
+  font-size: 0.85em;
+  padding: 0.1em 0.35em;
+  border-radius: 4px;
+  background: var(--vp-c-bg-soft);
+  color: var(--vp-c-text-1);
+}
+
+.controls {
+  display: flex;
+  align-items: center;
+  justify-content: space-between;
+  flex-wrap: wrap;
+  gap: 0.75rem;
+  margin-bottom: 1rem;
+}
+
+.reset-btn {
+  padding: 0.4rem 0.8rem;
+  border: 1px solid var(--vp-c-divider);
+  border-radius: 6px;
+  background: var(--vp-c-bg);
+  color: var(--vp-c-text-1);
+  font-size: 0.85rem;
+  cursor: pointer;
+  transition: border-color 0.2s, color 0.2s;
+}
+
+.reset-btn:hover {
+  border-color: var(--vp-c-brand-1);
+  color: var(--vp-c-brand-1);
+}
+
+.status {
+  font-size: 0.85rem;
+  color: var(--vp-c-text-2);
+  padding: 0.25rem 0.6rem;
+  border-radius: 999px;
+  background: var(--vp-c-bg-soft);
+}
+
+.status[data-state="ready"] {
+  color: var(--vp-c-brand-1);
+}
+
+.status[data-state="error"] {
+  color: var(--vp-c-danger-1, #d93f3f);
+}
+
+.grid {
+  display: grid;
+  grid-template-columns: 1fr 1fr;
+  gap: 1rem;
+}
+
+@media (max-width: 720px) {
+  .grid {
+    grid-template-columns: 1fr;
+  }
+}
+
+.pane {
+  display: flex;
+  flex-direction: column;
+  gap: 0.5rem;
+  min-width: 0;
+}
+
+.pane-label {
+  font-size: 0.85rem;
+  font-weight: 600;
+  color: var(--vp-c-text-2);
+  text-transform: uppercase;
+  letter-spacing: 0.04em;
+}
+
+textarea {
+  width: 100%;
+  min-height: 220px;
+  padding: 0.75rem;
+  border: 1px solid var(--vp-c-divider);
+  border-radius: 8px;
+  background: var(--vp-c-bg);
+  color: var(--vp-c-text-1);
+  font-family: var(--vp-font-family-mono);
+  font-size: 0.85rem;
+  line-height: 1.5;
+  resize: vertical;
+  transition: border-color 0.2s;
+}
+
+textarea:focus {
+  outline: none;
+  border-color: var(--vp-c-brand-1);
+}
+
+.decode-btn {
+  align-self: flex-start;
+  padding: 0.55rem 1.2rem;
+  border: none;
+  border-radius: 6px;
+  background: var(--vp-c-brand-1);
+  color: var(--vp-c-white, #fff);
+  font-weight: 600;
+  font-size: 0.9rem;
+  cursor: pointer;
+  transition: background 0.2s, opacity 0.2s;
+}
+
+.decode-btn:hover:not(:disabled) {
+  background: var(--vp-c-brand-2);
+}
+
+.decode-btn:disabled {
+  opacity: 0.55;
+  cursor: not-allowed;
+}
+
+.output {
+  margin: 0;
+  padding: 0.75rem;
+  min-height: 220px;
+  border: 1px solid var(--vp-c-divider);
+  border-radius: 8px;
+  background: var(--vp-c-bg-soft);
+  color: var(--vp-c-text-1);
+  font-family: var(--vp-font-family-mono);
+  font-size: 0.85rem;
+  line-height: 1.5;
+  white-space: pre-wrap;
+  word-break: break-word;
+  overflow: auto;
+}
+
+.output.error {
+  border-color: var(--vp-c-danger-1, #d93f3f);
+  color: var(--vp-c-danger-1, #d93f3f);
+  background: var(--vp-c-danger-soft, rgba(217, 63, 63, 0.08));
+}
+
+.output.muted {
+  color: var(--vp-c-text-3, var(--vp-c-text-2));
+  font-style: italic;
+}
+</style>
diff --git a/docs/.vitepress/config.mts b/docs/.vitepress/config.mts
index 540a54db..f9b33c6d 100644
--- a/docs/.vitepress/config.mts
+++ b/docs/.vitepress/config.mts
@@ -45,7 +45,8 @@ export default defineConfig({
           { text: 'Development contributions', link: '/participate/development' }
         ]
       },
-      { text: 'Compatible devices', link: '/devices/devices' }
+      { text: 'Compatible devices', link: '/devices/devices' },
+      { text: 'Web Parser', link: '/parser' }
     ],
     search: { provider: 'local' }
   },
diff --git a/docs/.vitepress/theme/index.ts b/docs/.vitepress/theme/index.ts
index 6ee44f89..a65055d0 100644
--- a/docs/.vitepress/theme/index.ts
+++ b/docs/.vitepress/theme/index.ts
@@ -3,12 +3,14 @@ import mediumZoom from 'medium-zoom'
 import { onMounted, watch, nextTick } from 'vue'
 import { useRoute } from 'vitepress'
 import DevicesTable from '../components/DevicesTable.vue'
+import WebParser from '../components/WebParser.vue'
 import './custom.css'
 
 export default {
   extends: DefaultTheme,
   enhanceApp({ app }) {
     app.component('DevicesTable', DevicesTable)
+    app.component('WebParser', WebParser)
   },
   setup() {
     const route = useRoute()
diff --git a/docs/parser.md b/docs/parser.md
new file mode 100644
index 00000000..0220afeb
--- /dev/null
+++ b/docs/parser.md
@@ -0,0 +1,34 @@
+---
+title: Web Parser
+aside: false
+---
+
+# Web Parser
+
+Decode a Bluetooth Low Energy advertisement directly in your browser. The
+Theengs Decoder library is compiled to WebAssembly and runs locally — your
+payload is never sent to a server.
+
+<WebParser />
+
+## How to capture an advertisement
+
+Most BLE scanners on a phone or computer expose the raw service data or
+manufacturer data fields of an advertisement. Copy the hex string and wrap
+it as a JSON object. At least one of `servicedata` or `manufacturerdata`
+must be present; the other fields below are optional but help match the
+right decoder.
+
+| Field | Description |
+|---|---|
+| `servicedata` | Service data payload, as a hex string. |
+| `servicedatauuid` | UUID of the service the data was advertised under. |
+| `manufacturerdata` | Manufacturer data payload, as a hex string. |
+| `name` | Advertised device name (used by some decoders). |
+| `mac` or `id` | Device MAC address (used by some decoders). |
+
+## Programmatic access
+
+The same decoder is also available as a Node.js package — see
+[Using with Node.js](./use/nodejs.md) — and as a Node-RED node — see
+[Using with Node-RED](./use/node-red.md).
diff --git a/nodejs/theengs-decoder/package.json b/nodejs/theengs-decoder/package.json
index 044dd0db..01c70147 100644
--- a/nodejs/theengs-decoder/package.json
+++ b/nodejs/theengs-decoder/package.json
@@ -28,6 +28,7 @@
   ],
   "scripts": {
     "build": "node scripts/build.js",
+    "build:web": "node scripts/build-web.js",
     "test": "node --test test/*.test.js"
   },
   "engines": {
diff --git a/nodejs/theengs-decoder/scripts/build-web.js b/nodejs/theengs-decoder/scripts/build-web.js
new file mode 100644
index 00000000..1295e861
--- /dev/null
+++ b/nodejs/theengs-decoder/scripts/build-web.js
@@ -0,0 +1,26 @@
+'use strict';
+
+const { execFileSync } = require('node:child_process');
+const { mkdirSync, copyFileSync } = require('node:fs');
+const path = require('node:path');
+
+const pkgDir = path.resolve(__dirname, '..');
+const repoRoot = path.resolve(pkgDir, '..', '..');
+const buildDir = path.join(pkgDir, 'build-web');
+const outDir = path.join(repoRoot, 'docs', '.vitepress', 'public', 'wasm');
+
+mkdirSync(buildDir, { recursive: true });
+mkdirSync(outDir, { recursive: true });
+
+const run = (cmd, args) =>
+  execFileSync(cmd, args, { cwd: buildDir, stdio: 'inherit' });
+
+run('emcmake', ['cmake', '-DBUILD_WASM_WEB=ON', repoRoot]);
+run('emmake', ['make', 'theengs_decoder_web', '-j']);
+
+copyFileSync(
+  path.join(buildDir, 'theengs_decoder_web.js'),
+  path.join(outDir, 'theengs_decoder_web.js'),
+);
+
+console.log(`Built ${path.relative(repoRoot, path.join(outDir, 'theengs_decoder_web.js'))}`);