diff --git a/package.json b/package.json
index 16d78d20e4..afacc50006 100644
--- a/package.json
+++ b/package.json
@@ -165,6 +165,7 @@
     "nightwatch_local_firefox": "nightwatch --config nightwatch.js --env firefox",
     "nightwatch_local_chrome": "nightwatch --config nightwatch.js --env chrome",
     "nightwatch_local_ballot": "nightwatch ./test-browser/tests/ballot.test.js --config nightwatch.js --env chrome ",
+    "nightwatch_local_usingWorker": "nightwatch ./test-browser/tests/usingWebWorker.test.js --config nightwatch.js --env chrome ",
     "nightwatch_local_libraryDeployment": "nightwatch ./test-browser/tests/libraryDeployment.test.js --config nightwatch.js --env chrome ",
     "nightwatch_local_solidityImport": "nightwatch ./test-browser/tests/solidityImport.test.js --config nightwatch.js --env chrome ",
     "nightwatch_local_recorder": "nightwatch ./test-browser/tests/recorder.test.js --config nightwatch.js --env chrome ",
diff --git a/src/app/compiler/compiler-helpers.js b/src/app/compiler/compiler-helpers.js
index a20ffa13b1..820e5c298f 100644
--- a/src/app/compiler/compiler-helpers.js
+++ b/src/app/compiler/compiler-helpers.js
@@ -1,5 +1,5 @@
 'use strict'
-import { canUseWorker } from './compiler-utils'
+import { canUseWorker, urlFromVersion } from './compiler-utils'
 import { Compiler } from 'remix-solidity'
 import CompilerAbstract from './compiler-abstract'
 
@@ -9,7 +9,7 @@ export const compile = async (compilationTargets, settings) => {
       const compiler = new Compiler(() => {})
       compiler.set('evmVersion', settings.evmVersion)
       compiler.set('optimize', settings.optimize)
-      compiler.loadVersion(canUseWorker(settings.version), settings.compilerUrl)
+      compiler.loadVersion(canUseWorker(settings.version), urlFromVersion(settings.version))
       compiler.event.register('compilationFinished', (success, compilationData, source) => {
         if (!success) return reject(compilationData)
         resolve(new CompilerAbstract(settings.version, compilationData, source))
diff --git a/src/app/compiler/compiler-sourceVerifier-fetchAndCompile.js b/src/app/compiler/compiler-sourceVerifier-fetchAndCompile.js
index 04956b5ac7..5df4e66390 100644
--- a/src/app/compiler/compiler-sourceVerifier-fetchAndCompile.js
+++ b/src/app/compiler/compiler-sourceVerifier-fetchAndCompile.js
@@ -1,7 +1,6 @@
 const ethutil = require('ethereumjs-util')
 import * as packageJson from '../../../package.json'
 import { Plugin } from '@remixproject/engine'
-import { urlFromVersion } from './compiler-utils'
 import { compile } from './compiler-helpers'
 import globalRegistry from '../../global/registry'
 
@@ -108,8 +107,7 @@ export default class FetchAndCompile extends Plugin {
       version: data.metadata.compiler.version,
       languageName: data.metadata.language,
       evmVersion: data.metadata.settings.evmVersion,
-      optimize: data.metadata.settings.optimizer.enabled,
-      compilerUrl: urlFromVersion(data.metadata.compiler.version)
+      optimize: data.metadata.settings.optimizer.enabled
     }
     try {
       setTimeout(_ => this.emit('compiling', settings), 0)
diff --git a/src/app/compiler/compiler-utils.js b/src/app/compiler/compiler-utils.js
index f7afcf9307..f7222f582d 100644
--- a/src/app/compiler/compiler-utils.js
+++ b/src/app/compiler/compiler-utils.js
@@ -1,48 +1,44 @@
 const semver = require('semver')
+const minixhr = require('minixhr')
 /* global Worker */
 
-export const baseUrl = 'https://solc-bin.ethereum.org/bin'
+export const baseURLBin = 'https://solc-bin.ethereum.org/bin'
+export const baseURLWasm = 'https://solc-bin.ethereum.org/wasm'
 
+export const pathToURL = {}
+
+/**
+ * Retrieves the URL of the given compiler version
+ * @param version is the version of compiler with or without 'soljson-v' prefix and .js postfix
+ */
 export function urlFromVersion (version) {
-  return `${baseUrl}/soljson-v${version}.js`
+  if (!version.startsWith('soljson-v')) version = 'soljson-v' + version
+  if (!version.endsWith('.js')) version = version + '.js'
+  return `${pathToURL[version]}/${version}`
 }
+
 /**
  * Checks if the worker can be used to load a compiler.
  * checks a compiler whitelist, browser support and OS.
  */
 export function canUseWorker (selectedVersion) {
-  // Following restrictions should be deleted when Solidity will release fixed versions of compilers.
-  // See https://github.com/ethereum/remix-ide/issues/2461
-  const isChrome = !!window.chrome
-  const os = retrieveOS()
-  // define a whitelist for Linux
-  const linuxWL = ['0.4.26', '0.5.3', '0.5.4', '0.5.5']
   const version = semver.coerce(selectedVersion)
-  // defining whitelist for chrome
-  let isFromWhiteList = false
-  switch (os) {
-    case 'Windows':
-      isFromWhiteList = semver.gt(version, '0.5.2') || version === '0.4.26'
-      break
-    case 'Linux':
-      isFromWhiteList = semver.gt(version, '0.5.13') || linuxWL.includes(version)
-      break
-    default :
-      isFromWhiteList = true
-  }
-  return browserSupportWorker() && (!isChrome || (isChrome && isFromWhiteList))
+  const isNightly = selectedVersion.includes('nightly')
+  return browserSupportWorker() && (
+    semver.gt(version, '0.6.3') ||
+    semver.gt(version, '0.3.6') && !isNightly
+  )
 }
 
 function browserSupportWorker () {
   return document.location.protocol !== 'file:' && Worker !== undefined
 }
 
-function retrieveOS () {
-  let osName = 'Unknown OS'
-  if (navigator.platform.indexOf('Win') !== -1) {
-    osName = 'Windows'
-  } else if (navigator.platform.indexOf('Linux') !== -1) {
-    osName = 'Linux'
-  }
-  return osName
+// returns a promise for minixhr
+export function promisedMiniXhr (url) {
+  return new Promise((resolve, reject) => {
+    minixhr(url, (json, event) => {
+      resolve({ json, event })
+    })
+  })
 }
diff --git a/src/app/editor/example-contracts.js b/src/app/editor/example-contracts.js
index 945abe0349..34c6ea9a64 100644
--- a/src/app/editor/example-contracts.js
+++ b/src/app/editor/example-contracts.js
@@ -1,5 +1,15 @@
 'use strict'
 
+const basic = `pragma solidity >=0.2.0 <0.7.0;
+
+/**
+ * @title Basic contract
+ */
+contract Basic {
+    uint someVar;
+    constructor() public {}
+}`
+
 const storage = `pragma solidity >=0.4.22 <0.7.0;
 
 /**
@@ -245,5 +255,6 @@ module.exports = {
   storage: { name: '1_Storage.sol', content: storage },
   owner: { name: '2_Owner.sol', content: owner },
   ballot: { name: '3_Ballot.sol', content: ballot },
-  ballot_test: { name: '4_Ballot_test.sol', content: ballotTest }
+  ballot_test: { name: '4_Ballot_test.sol', content: ballotTest },
+  basic: { name: 'basic.sol', content: basic }
 }
diff --git a/src/app/files/fileProvider.js b/src/app/files/fileProvider.js
index 116f42b368..1fa54ab11c 100644
--- a/src/app/files/fileProvider.js
+++ b/src/app/files/fileProvider.js
@@ -93,7 +93,10 @@ class FileProvider {
     cb = cb || function () {}
     var unprefixedpath = this.removePrefix(path)
     var exists = window.remixFileSystem.existsSync(unprefixedpath)
-    if (exists && window.remixFileSystem.readFileSync(unprefixedpath, 'utf8') === content) return true
+    if (exists && window.remixFileSystem.readFileSync(unprefixedpath, 'utf8') === content) {
+      cb()
+      return true
+    }
     if (!exists && unprefixedpath.indexOf('/') !== -1) {
       this.createDir(path)
     }
diff --git a/src/app/tabs/compile-tab.js b/src/app/tabs/compile-tab.js
index a5d8e4de10..52de47dd7e 100644
--- a/src/app/tabs/compile-tab.js
+++ b/src/app/tabs/compile-tab.js
@@ -116,6 +116,7 @@ class CompileTab extends ViewPlugin {
     this.fileManager.events.on('noFileSelected', this.data.eventHandlers.onNoFileSelected)
 
     this.data.eventHandlers.onCompilationFinished = (success, data, source) => {
+      this._view.errorContainer.appendChild(yo`<span data-id="compilationFinishedWith_${this.getCurrentVersion()}"></span>`)
       if (success) {
         // forwarding the event to the appManager infra
         this.emit('compilationFinished', source.target, source, 'soljson', data)
@@ -411,7 +412,7 @@ class CompileTab extends ViewPlugin {
   render () {
     if (this._view.el) return this._view.el
     this.onActivationInternal()
-    this._view.errorContainer = yo`<div class="${css.errorBlobs} p-4"></div>`
+    this._view.errorContainer = yo`<div class="${css.errorBlobs} p-4" data-id="compiledErrors" ></div>`
     this._view.contractSelection = this.contractSelection()
     this._view.compilerContainer = this.compilerContainer.render()
     this.compilerContainer.activate()
diff --git a/src/app/tabs/compileTab/compilerContainer.js b/src/app/tabs/compileTab/compilerContainer.js
index 5c51fd8ce9..b91f933bf3 100644
--- a/src/app/tabs/compileTab/compilerContainer.js
+++ b/src/app/tabs/compileTab/compilerContainer.js
@@ -1,12 +1,11 @@
 
 const yo = require('yo-yo')
-const minixhr = require('minixhr')
 const helper = require('../../../lib/helper')
 const addTooltip = require('../../ui/tooltip')
 const semver = require('semver')
 const modalDialogCustom = require('../../ui/modal-dialog-custom')
 const css = require('../styles/compile-tab-styles')
-import { canUseWorker } from '../../compiler/compiler-utils'
+import { canUseWorker, baseURLBin, baseURLWasm, urlFromVersion, pathToURL, promisedMiniXhr } from '../../compiler/compiler-utils'
 
 class CompilerContainer {
 
@@ -24,8 +23,7 @@ class CompilerContainer {
       timeout: 300,
       allversions: null,
       selectedVersion: null,
-      defaultVersion: 'soljson-v0.6.6+commit.6c089d02.js', // this default version is defined: in makeMockCompiler (for browser test) and in package.json (downloadsolc_root) for the builtin compiler
-      baseurl: 'https://solc-bin.ethereum.org/bin'
+      defaultVersion: 'soljson-v0.6.6+commit.6c089d02.js' // this default version is defined: in makeMockCompiler (for browser test) and in package.json (downloadsolc_root) for the builtin compiler
     }
   }
 
@@ -383,13 +381,13 @@ class CompilerContainer {
       if (this.data.selectedVersion.indexOf('soljson') !== 0 || helper.checkSpecialChars(this.data.selectedVersion)) {
         return console.log('loading ' + this.data.selectedVersion + ' not allowed')
       }
-      url = `${this.data.baseurl}/${this.data.selectedVersion}`
+      url = `${urlFromVersion(this.data.selectedVersion)}`
     }
 
     // Workers cannot load js on "file:"-URLs and we get a
     // "Uncaught RangeError: Maximum call stack size exceeded" error on Chromium,
     // resort to non-worker version in that case.
-    if (canUseWorker(this.data.selectedVersion)) {
+    if (this.data.selectedVersion !== 'builtin' && canUseWorker(this.data.selectedVersion)) {
       this.compileTabLogic.compiler.loadVersion(true, url)
       this.setVersionText('(loading using worker)')
     } else {
@@ -413,27 +411,42 @@ class CompilerContainer {
     if (this._view.version) this._view.version.innerText = text
   }
 
-  fetchAllVersion (callback) {
-    minixhr(`${this.data.baseurl}/list.json`, (json, event) => {
-      // @TODO: optimise and cache results to improve app loading times #2461
-      var allversions, selectedVersion
-      if (event.type !== 'error') {
-        try {
-          const data = JSON.parse(json)
-          allversions = data.builds.slice().reverse()
-          selectedVersion = this.data.defaultVersion
-          if (this.queryParams.get().version) selectedVersion = this.queryParams.get().version
-        } catch (e) {
-          addTooltip('Cannot load compiler version list. It might have been blocked by an advertisement blocker. Please try deactivating any of them from this page and reload.')
-        }
-      } else {
-        allversions = [{ path: 'builtin', longVersion: 'latest local version' }]
-        selectedVersion = 'builtin'
+  // fetching both normal and wasm builds and creating a [version, baseUrl] map
+  async fetchAllVersion (callback) {
+    let allVersions, selectedVersion, allVersionsWasm
+    // fetch normal builds
+    const binRes = await promisedMiniXhr(`${baseURLBin}/list.json`)
+    // fetch wasm builds
+    const wasmRes = await promisedMiniXhr(`${baseURLWasm}/list.json`)
+    if (binRes.event.type === 'error' && wasmRes.event.type === 'error') {
+      allVersions = [{ path: 'builtin', longVersion: 'latest local version' }]
+      selectedVersion = 'builtin'
+      callback(allVersions, selectedVersion)
+    }
+    try {
+      allVersions = JSON.parse(binRes.json).builds.slice().reverse()
+      selectedVersion = this.data.defaultVersion
+      if (this.queryParams.get().version) selectedVersion = this.queryParams.get().version
+      if (wasmRes.event.type !== 'error') {
+        allVersionsWasm = JSON.parse(wasmRes.json).builds.slice().reverse()
       }
-      callback(allversions, selectedVersion)
-    })
+    } catch (e) {
+      addTooltip('Cannot load compiler version list. It might have been blocked by an advertisement blocker. Please try deactivating any of them from this page and reload. Error: ' + e)
+    }
+    // replace in allVersions those compiler builds which exist in allVersionsWasm with new once
+    if (allVersionsWasm && allVersions) {
+      allVersions.forEach((compiler, index) => {
+        const wasmIndex = allVersionsWasm.findIndex(wasmCompiler => { return wasmCompiler.longVersion === compiler.longVersion })
+        if (wasmIndex !== -1) {
+          allVersions[index] = allVersionsWasm[wasmIndex]
+          pathToURL[compiler.path] = baseURLWasm
+        } else {
+          pathToURL[compiler.path] = baseURLBin
+        }
+      })
+    }
+    callback(allVersions, selectedVersion)
   }
-
   scheduleCompilation () {
     if (!this.config.get('autoCompile')) return
     if (this.data.compileTimeout) window.clearTimeout(this.data.compileTimeout)
diff --git a/src/app/tabs/test-tab.js b/src/app/tabs/test-tab.js
index 2dfb270a9f..abc9986a1d 100644
--- a/src/app/tabs/test-tab.js
+++ b/src/app/tabs/test-tab.js
@@ -4,7 +4,7 @@ var tooltip = require('../ui/tooltip')
 var css = require('./styles/test-tab-styles')
 var remixTests = require('remix-tests')
 import { ViewPlugin } from '@remixproject/engine'
-import { canUseWorker, baseUrl } from '../compiler/compiler-utils'
+import { canUseWorker, urlFromVersion } from '../compiler/compiler-utils'
 
 const TestTabLogic = require('./testTab/testTab')
 
@@ -301,7 +301,7 @@ module.exports = class TestTab extends ViewPlugin {
       let runningTest = {}
       runningTest[path] = { content }
       const {currentVersion, evmVersion, optimize} = this.compileTab.getCurrentCompilerConfig()
-      const currentCompilerUrl = baseUrl + '/' + currentVersion
+      const currentCompilerUrl = urlFromVersion(currentVersion)
       const compilerConfig = {
         currentCompilerUrl,
         evmVersion,
@@ -327,7 +327,7 @@ module.exports = class TestTab extends ViewPlugin {
       const runningTest = {}
       runningTest[testFilePath] = { content }
       const {currentVersion, evmVersion, optimize} = this.compileTab.getCurrentCompilerConfig()
-      const currentCompilerUrl = baseUrl + '/' + currentVersion
+      const currentCompilerUrl = urlFromVersion(currentVersion)
       const compilerConfig = {
         currentCompilerUrl,
         evmVersion,
diff --git a/src/lib/helper.js b/src/lib/helper.js
index cda3bfe519..15f692fcc1 100644
--- a/src/lib/helper.js
+++ b/src/lib/helper.js
@@ -84,4 +84,3 @@ function find (args, query) {
   })
   return isMatch
 }
-
diff --git a/test-browser/commands/noWorkerErrorFor.js b/test-browser/commands/noWorkerErrorFor.js
new file mode 100644
index 0000000000..614e710c14
--- /dev/null
+++ b/test-browser/commands/noWorkerErrorFor.js
@@ -0,0 +1,28 @@
+const EventEmitter = require('events')
+
+class NoWorkerErrorFor extends EventEmitter {
+  command (version) {
+    this.api.perform((done) => {
+      noWorkerErrorFor(this.api, version, () => {
+        done()
+        this.emit('complete')
+      })
+    })
+    return this
+  }
+}
+
+function noWorkerErrorFor (browser, version, callback) {
+  browser
+    .setSolidityCompilerVersion(version)
+    .click('*[data-id="compilerContainerCompileBtn"]')
+    .waitForElementPresent('*[data-id="compilationFinishedWith_' + version + '"]', 10000)
+    .notContainsText('*[data-id="compiledErrors"]', 'worker error:undefined')
+    .notContainsText('*[data-id="compiledErrors"]', 'Uncaught RangeError: Maximum call stack size exceeded')
+    .notContainsText('*[data-id="compiledErrors"]', 'RangeError: Maximum call stack size exceeded')
+    .perform(() => {
+      callback()
+    })
+}
+
+module.exports = NoWorkerErrorFor
diff --git a/test-browser/tests/runAndDeploy.js b/test-browser/tests/runAndDeploy.js
index 7f705171b3..1fddeedb54 100644
--- a/test-browser/tests/runAndDeploy.js
+++ b/test-browser/tests/runAndDeploy.js
@@ -31,8 +31,7 @@ module.exports = {
     .assert.elementNotPresent('*[data-id="settingsRemixRunSignMsgHash"]')
     .assert.elementNotPresent('*[data-id="settingsRemixRunSignMsgSignature"]')
     .modalFooterOKClick()
-    .pause(2000)
-    .waitForElementPresent('*[data-id="modalDialogContainer"]')
+    .waitForElementPresent('*[data-id="modalDialogContainer"]', 12000)
     .assert.elementPresent('*[data-id="settingsRemixRunSignMsgHash"]')
     .assert.elementPresent('*[data-id="settingsRemixRunSignMsgSignature"]')
     .modalFooterOKClick()
@@ -145,8 +144,8 @@ module.exports = {
     .clickLaunchIcon('udapp')
     .waitForElementPresent('*[data-id="Deploy - transact (not payable)"]')
     .click('*[data-id="Deploy - transact (not payable)"]')
-    .pause(2000)
-    .waitForElementPresent('*[data-id="modalDialogContainer"]')
+    .waitForElementPresent('*[data-id="modalDialogContainer"]', 15000)
+    .pause(10000)
     .assert.containsText('*[data-id="modalDialogModalBody"]', 'You are creating a transaction on the main network. Click confirm if you are sure to continue.')
     .modalFooterCancelClick()
   },
diff --git a/test-browser/tests/solidityUnittests.test.js b/test-browser/tests/solidityUnittests.test.js
index 3a4882ad51..cdb99c4e03 100644
--- a/test-browser/tests/solidityUnittests.test.js
+++ b/test-browser/tests/solidityUnittests.test.js
@@ -86,7 +86,7 @@ module.exports = {
     .scrollAndClick('*[data-id="testTabRunTestsTabRunAction"]')
     .pause(5000)
     .click('*[data-id="testTabRunTestsTabStopAction"]')
-    .pause(2000)
+    .pause(1000)
     .assert.containsText('*[data-id="testTabRunTestsTabStopAction"]', 'Stopping')
     .waitForElementPresent('*[data-id="testTabSolidityUnitTestsOutputheader"]', 40000)
     .assert.containsText('*[data-id="testTabSolidityUnitTestsOutput"]', 'browser/ks2b_test.sol')
diff --git a/test-browser/tests/usingWebWorker.test.js b/test-browser/tests/usingWebWorker.test.js
new file mode 100644
index 0000000000..c59da319d3
--- /dev/null
+++ b/test-browser/tests/usingWebWorker.test.js
@@ -0,0 +1,37 @@
+'use strict'
+var examples = require('../../src/app/editor/example-contracts')
+var init = require('../helpers/init')
+var sauce = require('./sauce')
+
+var sources = [
+  {'browser/basic.sol': {content: examples.basic.content}}
+]
+
+module.exports = {
+  before: function (browser, done) {
+    init(browser, done)
+  },
+  '@sources': function () {
+    return sources
+  },
+  'Using Web Worker': function (browser) {
+    browser
+    .waitForElementVisible('*[data-id="remixIdeIconPanel"]', 10000)
+    .clickLaunchIcon('fileExplorers')
+    .openFile('browser/basic.sol')
+    .clickLaunchIcon('solidity')
+    .execute(() => {
+      document.getElementById('nightlies').checked = true
+    })
+    .noWorkerErrorFor('soljson-v0.3.4+commit.7dab890.js')
+    .noWorkerErrorFor('soljson-v0.6.5+commit.f956cc89.js')
+    .noWorkerErrorFor('soljson-v0.6.8-nightly.2020.5.14+commit.a6d0067b.js')
+    .noWorkerErrorFor('soljson-v0.6.0-nightly.2019.12.17+commit.d13438ee.js')
+    .noWorkerErrorFor('soljson-v0.4.26+commit.4563c3fc.js')
+    .execute(() => {
+      document.getElementById('nightlies').checked = false
+    })
+  },
+
+  tearDown: sauce
+}