diff --git a/demo/demo.js b/demo/demo.js
index 7826a4f7..20f155ba 100644
--- a/demo/demo.js
+++ b/demo/demo.js
@@ -6,37 +6,3 @@ window.addEventListener('message', function (event) {
     window.document.title = event.data.type
   }
 })
-
-var EMBED_DOM_CLASSES = [
-  {
-    selector: '.typeform-widget',
-    attribute: 'data-url'
-  }, {
-    selector: '.typeform-share',
-    attribute: 'href'
-  }, {
-    selector: '.typeform-full',
-    attribute: 'src'
-  }
-]
-
-const addQueryStringToUrl = (url, queryString) => {
-  return /\?/.test(url) ? `${url}&${queryString}` : `${url}?${queryString}`
-}
-
-window.addEventListener('DOMContentLoaded', function () {
-  var queryString = window.location.search.substring(1)
-  if (queryString.length === 0) {
-    return
-  }
-
-  EMBED_DOM_CLASSES
-    .forEach(function (embed) {
-      var attribute = embed.attribute
-      var embeds = document.querySelectorAll(embed.selector)
-      embeds.forEach(function (embed) {
-        var embedAttr = embed.getAttribute(attribute)
-        embed.setAttribute(attribute, addQueryStringToUrl(embedAttr, queryString))
-      })
-    })
-})
diff --git a/demo/full.html b/demo/full.html
index cf7dc17b..d0a5c1d4 100644
--- a/demo/full.html
+++ b/demo/full.html
@@ -21,7 +21,7 @@
       width="100%"
       height="100%"
       frameborder="0"
-      src="./form/mock.html"
+      src="./form/mock.html#foobar=hello"
     ></iframe>
 
     <script type="text/javascript" src="embed.js"></script>
diff --git a/demo/index.html b/demo/index.html
index 159ffbd0..5661e950 100644
--- a/demo/index.html
+++ b/demo/index.html
@@ -14,6 +14,7 @@ <h2>Embed snippet</h2>
     <ul>
       <li><a href="./widget-v3.html">Widget accepting form and embed library version as URL parameters</a></li>
       <li><a href="./widget.html">Widget *</a></li>
+      <li><a href="./widget-legacy.html">Widget with legacy hidden fields *</a></li>
       <li><a href="./widget-v2.html">Widget with long text</a></li>
       <li><a href="./multi-widget.html">Multiple widgets</a></li>
       <li><a href="./full.html">Full page *</a></li>
diff --git a/demo/popup.html b/demo/popup.html
index 55e68d62..94a742ec 100644
--- a/demo/popup.html
+++ b/demo/popup.html
@@ -43,7 +43,7 @@
   <body>
     <a
       class="typeform-share popup"
-      href="./form/mock.html"
+      href="./form/mock.html#foobar=hello"
       data-mode="popup"
       data-submit-close-delay="4"
       target="_blank"
@@ -51,9 +51,10 @@
       Launch me as a popup!
     </a>
 
+    <!-- uses legacy hidden field in query param -->
     <a
       class="typeform-share popup"
-      href="./form/mock.html"
+      href="./form/mock.html?foobar=hello"
       data-mode="drawer_left"
       data-submit-close-delay="4"
       target="_blank"
@@ -63,7 +64,7 @@
 
     <a
       class="typeform-share popup"
-      href="./form/mock.html"
+      href="./form/mock.html#foobar=hello"
       data-mode="drawer_right"
       data-width="400"
       data-submit-close-delay="4"
@@ -76,7 +77,7 @@
 
     <a
       class="typeform-share popover"
-      href="./form/mock.html"
+      href="./form/mock.html#foobar=hello"
       data-mode="popover"
       data-width="500"
       data-height="600"
diff --git a/demo/widget-legacy.html b/demo/widget-legacy.html
new file mode 100644
index 00000000..1a7cbaf2
--- /dev/null
+++ b/demo/widget-legacy.html
@@ -0,0 +1,19 @@
+<!DOCTYPE html>
+<html lang="en">
+  <head>
+    <title>Widget example</title>
+    <meta charset="utf-8" />
+    <meta content='width=device-width, initial-scale=1.0, maximum-scale=1.0, user-scalable=0' name='viewport' />
+    <link rel="stylesheet" href="demo.css" />
+  </head>
+  <body>
+    <div
+      class="typeform-widget"
+      data-url="./form/mock.html?foobar=hello"
+      style="width:100%; height:500px;"
+    ></div>
+
+    <script type="text/javascript" src="demo.js"></script>
+    <script type="text/javascript" src="embed.js"></script>
+  </body>
+</html>
diff --git a/demo/widget.html b/demo/widget.html
index 18e627c5..f83b181b 100644
--- a/demo/widget.html
+++ b/demo/widget.html
@@ -1,7 +1,7 @@
 <!DOCTYPE html>
 <html lang="en">
   <head>
-    <title>Widget example</title>
+    <title>Widget (legacy hidden fields) example</title>
     <meta charset="utf-8" />
     <meta content='width=device-width, initial-scale=1.0, maximum-scale=1.0, user-scalable=0' name='viewport' />
     <link rel="stylesheet" href="demo.css" />
@@ -9,7 +9,7 @@
   <body>
     <div
       class="typeform-widget"
-      data-url="./form/mock.html"
+      data-url="./form/mock.html#foobar=hello"
       style="width:100%; height:500px;"
     ></div>
 
diff --git a/e2e/spec/functional/popup.spec.js b/e2e/spec/functional/popup.spec.js
index 6c642d00..83d4b731 100644
--- a/e2e/spec/functional/popup.spec.js
+++ b/e2e/spec/functional/popup.spec.js
@@ -23,7 +23,7 @@ Object.keys(popupModes).forEach(popupMode => {
         openPopup(popupMode)
       })
 
-      it('Passes query string parameter', () => {
+      it('Passes hidden field parameter', () => {
         cy.get(IFRAME_SELECTOR).should('have.attr', 'src').and('match', /foobar=hello/)
       })
 
diff --git a/e2e/spec/functional/widget.spec.js b/e2e/spec/functional/widget.spec.js
index 32f9c551..9ad184c6 100644
--- a/e2e/spec/functional/widget.spec.js
+++ b/e2e/spec/functional/widget.spec.js
@@ -1,4 +1,4 @@
-import { open, testEmbeddedForm, openOnMobile, testEmbedFormOnMobile } from '../../cypress-utils'
+import { open, testEmbeddedForm, openOnMobile, testEmbedFormOnMobile, IFRAME_SELECTOR } from '../../cypress-utils'
 
 describe('Embed Widget in div with position:absolute on mobile', () => {
   it('Loads correctly the basic embed widget', () => {
@@ -9,17 +9,61 @@ describe('Embed Widget in div with position:absolute on mobile', () => {
 
 describe('Basic Embed Widget', () => {
   describe('On Desktop', () => {
-    it('Loads correctly the basic embed widget', () => {
+    before(() => {
       open('/widget.html')
+    })
+
+    it('Loads correctly the basic embed widget', () => {
       testEmbeddedForm()
     })
+
+    it('Passes hidden field parameter', () => {
+      cy.get(IFRAME_SELECTOR).should('have.attr', 'src').and('match', /foobar=hello/)
+    })
   })
 
   describe('On Mobile', () => {
-    it('Loads correctly the basic embed widget', () => {
+    before(() => {
       openOnMobile('/widget.html')
+    })
+
+    it('Loads correctly the basic embed widget', () => {
+      testEmbedFormOnMobile()
+    })
+
+    it('Passes hidden field parameter', () => {
+      cy.get(IFRAME_SELECTOR).should('have.attr', 'src').and('match', /foobar=hello/)
+    })
+  })
+})
+
+describe('Basic Embed Widget with Legacy Hidden Fields', () => {
+  describe('On Desktop', () => {
+    before(() => {
+      open('/widget-legacy.html')
+    })
+
+    it('Loads correctly the basic embed widget', () => {
+      testEmbeddedForm()
+    })
+
+    it('Passes hidden field parameter', () => {
+      cy.get(IFRAME_SELECTOR).should('have.attr', 'src').and('match', /foobar=hello/)
+    })
+  })
+
+  describe('On Mobile', () => {
+    before(() => {
+      openOnMobile('/widget-legacy.html')
+    })
+
+    it('Loads correctly the basic embed widget', () => {
       testEmbedFormOnMobile()
     })
+
+    it('Passes hidden field parameter', () => {
+      cy.get(IFRAME_SELECTOR).should('have.attr', 'src').and('match', /foobar=hello/)
+    })
   })
 })
 
@@ -27,16 +71,31 @@ describe('Full Page Embed Widget', () => {
   const iframe = '#typeform-full'
 
   describe('On Desktop', () => {
+    before(() => {
+      open('/full.html')
+    })
+
     it('Loads correctly the Full Page widget', () => {
       open('/full.html')
       testEmbeddedForm(iframe)
     })
+
+    it('Passes hidden field parameter', () => {
+      cy.get(iframe).should('have.attr', 'src').and('match', /foobar=hello/)
+    })
   })
 
   describe('On Mobile', () => {
-    it('Loads correctly the Full Page widget', () => {
+    before(() => {
       openOnMobile('/full.html')
+    })
+
+    it('Loads correctly the Full Page widget', () => {
       testEmbeddedForm(iframe) // full page widget behaves the same as on desktop (no modal window)
     })
+
+    it('Passes hidden field parameter', () => {
+      cy.get(iframe).should('have.attr', 'src').and('match', /foobar=hello/)
+    })
   })
 })
diff --git a/package.json b/package.json
index 5454c2ca..73bcf6d5 100644
--- a/package.json
+++ b/package.json
@@ -22,7 +22,7 @@
     "build": "./scripts/build.sh",
     "serve-demo": "PORT=8080 yarn serve -S demo",
     "start": "NODE_ENV=development webpack-dev-server -d --config webpack.config.js --content-base ./demo",
-    "test": "yarn lint && yarn test:unit && yarn test:visual && yarn test:functional",
+    "test": "yarn lint && yarn test:unit && yarn test:functional && yarn test:visual",
     "lint": "yarn eslint ./src --ext .js --ignore-path .eslintignore --max-warnings=0",
     "test:unit": "yarn jest",
     "test:unit:watch": "yarn jest --watch",
diff --git a/src/core/utils/index.js b/src/core/utils/index.js
index efc7454d..31ad22e3 100644
--- a/src/core/utils/index.js
+++ b/src/core/utils/index.js
@@ -22,13 +22,7 @@ export const broadcastMessage = (embedId, event) => {
 }
 
 export const updateQueryStringParameter = (key, value, uri) => {
-  const re = new RegExp(`([?&])${key}=.*?(&|$)`, 'i')
-  const separator = uri.indexOf('?') !== -1 ? '&' : '?'
-  if (uri.match(re)) {
-    return uri.replace(re, `$1${key}=${value}$2`)
-  }
-
-  return `${uri + separator + key}=${value}`
+  return appendParamsToUrl(uri, { [key]: value })
 }
 
 export const appendParamsToUrl = (url, params) => {
@@ -36,7 +30,8 @@ export const appendParamsToUrl = (url, params) => {
   const {
     query,
     origin,
-    pathname
+    pathname,
+    hash
   } = UrlParse(url, true)
   const path = pathname.replace(/\/$/, '') // remove trailing slash
   const parameters = Object.assign({}, query, params)
@@ -47,7 +42,7 @@ export const appendParamsToUrl = (url, params) => {
     )
   })
 
-  return `${origin}${path}?${queryParameters.join('&')}`
+  return `${origin}${path}?${queryParameters.join('&')}${hash}`
 }
 
 export const replaceExistingKeys = (obj, replacer) => {
diff --git a/src/core/utils/index.spec.js b/src/core/utils/index.spec.js
index 91f169c4..6f8af76f 100644
--- a/src/core/utils/index.spec.js
+++ b/src/core/utils/index.spec.js
@@ -8,10 +8,20 @@ jest.mock('./message-propagation')
 
 describe('Utilities', () => {
   describe('appendParamsToUrl', () => {
-    it('should append parameters to url correctly', () => {
-      fixtures.urls.forEach((fixture) => {
+    fixtures.urls.forEach((fixture) => {
+      it(`should append parameters correctly to url ${fixture.url}`, () => {
         const result = utils.appendParamsToUrl(fixture.url, fixture.params)
+        expect(result).toEqual(fixture.expected)
+      })
+    })
+  })
 
+  describe('updateQueryStringParameter', () => {
+    fixtures.urls.forEach((fixture) => {
+      it(`should update parameter correctly on url ${fixture.url}`, () => {
+        const key = Object.keys(fixture.params)[0]
+        const value = Object.values(fixture.params)[0]
+        const result = utils.updateQueryStringParameter(key, value, fixture.url)
         expect(result).toEqual(fixture.expected)
       })
     })
diff --git a/test/fixtures.js b/test/fixtures.js
index b18bed28..3814a2ac 100644
--- a/test/fixtures.js
+++ b/test/fixtures.js
@@ -1,19 +1,27 @@
 export const urls = [{
   url: 'https://admin.typeform.com/to/bXK16J',
   params: { 'hola': 'mandarina' },
-  expected: 'https://admin.typeform.com/to/bXK16J?hola=mandarina',
+  expected: 'https://admin.typeform.com/to/bXK16J?hola=mandarina'
 }, {
   url: 'https://url.com?hola=true',
   params: { 'mandarina': 'apple' },
-  expected: 'https://url.com?hola=true&mandarina=apple',
+  expected: 'https://url.com?hola=true&mandarina=apple'
 }, {
   url: 'https://url.com/',
   params: { 'mandarina': 'apple' },
-  expected: 'https://url.com?mandarina=apple',
+  expected: 'https://url.com?mandarina=apple'
 }, {
   url: 'https://url.com?mandarina=true',
   params: { 'mandarina': 'apple' },
-  expected: 'https://url.com?mandarina=apple',
+  expected: 'https://url.com?mandarina=apple'
+}, {
+  url: 'https://url.com?mandarina=true#naranja=yum',
+  params: { 'mandarina': 'apple' },
+  expected: 'https://url.com?mandarina=apple#naranja=yum'
+}, {
+  url: 'https://url.com#naranja=yum',
+  params: { 'mandarina': 'apple' },
+  expected: 'https://url.com?mandarina=apple#naranja=yum'
 }]
 
 export const userAgents = [{
@@ -21,35 +29,35 @@ export const userAgents = [{
   ua: 'Mozilla/5.0 (iPod touch; CPU iPhone OS 10_2_1 like Mac OS X) AppleWebKit/602.4.6 (KHTML, like Gecko) Version/10.0 Mobile/14D27 Safari/602.1',
   isMobile: true,
   isSafari: true,
-  isIOSDevice: true,
+  isIOSDevice: true
 }, {
   name: 'Chrome mobile (Nexus)',
   ua: 'Mozilla/5.0 (Linux; Android 4.0.4; Galaxy Nexus Build/IMM76B) AppleWebKit/535.19 (KHTML, like Gecko) Chrome/18.0.1025.133 Mobile Safari/535.19',
   isMobile: true,
   isSafari: false,
-  isIOSDevice: false,
+  isIOSDevice: false
 }, {
   name: 'Safari iOS 9 (iPad)',
   ua: 'Mozilla/5.0 (iPad; CPU OS 9_1 like Mac OS X) AppleWebKit/601.1.46 (KHTML, like Gecko) Version/9.0 Mobile/13B137 Safari/601.1',
   isMobile: true,
   isSafari: true,
-  isIOSDevice: true,
+  isIOSDevice: true
 }, {
   name: 'Chrome iOS 9 (iPhone)',
   ua: 'Mozilla/5.0 (iPhone; CPU iPhone OS 9_1 like Mac OS X) AppleWebKit/601.1 (KHTML, like Gecko) CriOS/56.0.2924.87 Mobile/13B143 Safari/601.1.46',
   isMobile: true,
   isSafari: true, // ?
-  isIOSDevice: true,
+  isIOSDevice: true
 }, {
   name: 'Edge Windows',
   ua: 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/42.0.2311.135 Safari/537.36 Edge/12.10240',
   isMobile: false,
   isSafari: false,
-  isIOSDevice: false,
+  isIOSDevice: false
 }, {
   name: 'Safari Mac OS',
   ua: 'Mozilla/5.0 (Macintosh; Intel Mac OS X 10_9_3) AppleWebKit/537.75.14 (KHTML, like Gecko) Version/7.0.3 Safari/7046A194A',
   isMobile: false,
   isSafari: true,
-  isIOSDevice: false,
+  isIOSDevice: false
 }]
