diff --git a/examples/html-editor/index.js b/examples/html-editor/index.js
index 4d8fe7ab..307cb34a 100644
--- a/examples/html-editor/index.js
+++ b/examples/html-editor/index.js
@@ -10,8 +10,23 @@ let y = new Y({
   }
 })
 window.yXml = y
+window.yXmlType = y.get('xml', Y.XmlFragment)
 window.onload = function () {
   console.log('start!')
   // Bind children of XmlFragment to the document.body
-  y.get('xml', Y.XmlFragment).bindToDom(document.body)
+  window.yXmlType.bindToDom(document.body)
+}
+window.undoManager = new Y.utils.UndoManager(window.yXmlType)
+
+document.onkeydown = function interceptUndoRedo (e) {
+  if (e.keyCode === 90 && e.ctrlKey) {
+    if (!e.shiftKey) {
+      console.info('Undo!')
+      window.undoManager.undo()
+    } else {
+      console.info('Redo!')
+      window.undoManager.redo()
+    }
+    e.preventDefault()
+  }
 }
diff --git a/src/Store/StateStore.js b/src/Store/StateStore.js
index a4492f2c..0d547e87 100644
--- a/src/Store/StateStore.js
+++ b/src/Store/StateStore.js
@@ -38,6 +38,10 @@ export default class StateStore {
   }
   setState (user, state) {
     // TODO: modify missingi structs here
+    const beforeState = this.y._transaction.beforeState
+    if (!beforeState.has(user)) {
+      beforeState.set(user, this.getState(user))
+    }
     this.state.set(user, state)
   }
 }
diff --git a/src/Struct/Item.js b/src/Struct/Item.js
index ef6e41b4..62a598f3 100644
--- a/src/Struct/Item.js
+++ b/src/Struct/Item.js
@@ -52,6 +52,19 @@ export default class Item {
     this._parentSub = null
     this._deleted = false
   }
+  /**
+   * Copy the effect of struct
+   */
+  _copy () {
+    let struct = new this.constructor()
+    struct._origin = this._left
+    struct._left = this._left
+    struct._right = this
+    struct._right_origin = this
+    struct._parent = this._parent
+    struct._parentSub = this._parentSub
+    return struct
+  }
   get _lastId () {
     return new ID(this._id.user, this._id.clock + this._length - 1)
   }
@@ -83,6 +96,7 @@ export default class Item {
       del._integrate(y, true)
     }
     transactionTypeChanged(y, this._parent, this._parentSub)
+    y._transaction.deletedStructs.add(this)
   }
   /**
    * This is called right before this struct receives any children.
diff --git a/src/Struct/ItemJSON.js b/src/Struct/ItemJSON.js
index 3c5fba14..8c6610bc 100644
--- a/src/Struct/ItemJSON.js
+++ b/src/Struct/ItemJSON.js
@@ -6,6 +6,11 @@ export default class ItemJSON extends Item {
     super()
     this._content = null
   }
+  _copy () {
+    let struct = super._copy()
+    struct._content = this._content
+    return struct
+  }
   get _length () {
     return this._content.length
   }
diff --git a/src/Struct/ItemString.js b/src/Struct/ItemString.js
index 3409ae42..50ea4839 100644
--- a/src/Struct/ItemString.js
+++ b/src/Struct/ItemString.js
@@ -6,6 +6,11 @@ export default class ItemString extends Item {
     super()
     this._content = null
   }
+  _copy () {
+    let struct = super._copy()
+    struct._content = this._content
+    return struct
+  }
   get _length () {
     return this._content.length
   }
diff --git a/src/Struct/Type.js b/src/Struct/Type.js
index a865d4b3..bf1952cd 100644
--- a/src/Struct/Type.js
+++ b/src/Struct/Type.js
@@ -37,6 +37,48 @@ export default class Type extends Item {
     this._start = null
     this._y = null
     this._eventHandler = new EventHandler()
+    this._deepEventHandler = new EventHandler()
+  }
+  _callEventHandler (event) {
+    this._eventHandler.callEventListeners(event)
+    let type = this
+    while (type !== this._y) {
+      type._deepEventHandler.callEventListeners(event)
+      type = type._parent
+    }
+  }
+  _copy (undeleteChildren) {
+    let copy = super._copy()
+    let map = new Map()
+    copy._map = map
+    for (let [key, value] of this._map) {
+      if (undeleteChildren.has(value) || !value.deleted) {
+        let _item = value._copy(undeleteChildren)
+        _item._parent = copy
+        map.set(key, value._copy(undeleteChildren))
+      }
+    }
+    let prevUndeleted = null
+    copy._start = null
+    let item = this._start
+    while (item !== null) {
+      if (undeleteChildren.has(item) || !item.deleted) {
+        let _item = item._copy(undeleteChildren)
+        _item._left = prevUndeleted
+        _item._origin = prevUndeleted
+        _item._right = null
+        _item._right_origin = null
+        _item._parent = copy
+        if (prevUndeleted === null) {
+          copy._start = _item
+        } else {
+          prevUndeleted._right = _item
+        }
+        prevUndeleted = _item
+      }
+      item = item._right
+    }
+    return copy
   }
   _transact (f) {
     const y = this._y
@@ -49,9 +91,15 @@ export default class Type extends Item {
   observe (f) {
     this._eventHandler.addEventListener(f)
   }
+  observeDeep (f) {
+    this._deepEventHandler.addEventListener(f)
+  }
   unobserve (f) {
     this._eventHandler.removeEventListener(f)
   }
+  unobserveDeep (f) {
+    this._deepEventHandler.removeEventListener(f)
+  }
   _integrate (y) {
     y._transaction.newTypes.add(this)
     super._integrate(y)
diff --git a/src/Transaction.js b/src/Transaction.js
index 95cd3a5c..3376620a 100644
--- a/src/Transaction.js
+++ b/src/Transaction.js
@@ -5,8 +5,10 @@ export default class Transaction {
     // types added during transaction
     this.newTypes = new Set()
     // changed types (does not include new types)
-    // maps from type to parentSubs (item.parentSub = null for array elements)
+    // maps from type to parentSubs (item._parentSub = null for array elements)
     this.changedTypes = new Map()
+    this.deletedStructs = new Set()
+    this.beforeState = new Map()
   }
 }
 
diff --git a/src/Type/YArray.js b/src/Type/YArray.js
index 58b60f15..85a9bb88 100644
--- a/src/Type/YArray.js
+++ b/src/Type/YArray.js
@@ -11,7 +11,7 @@ class YArrayEvent {
 
 export default class YArray extends Type {
   _callObserver (parentSubs, remote) {
-    this._eventHandler.callEventListeners(new YArrayEvent(this, remote))
+    this._callEventHandler(new YArrayEvent(this, remote))
   }
   get (pos) {
     let n = this._start
diff --git a/src/Type/YMap.js b/src/Type/YMap.js
index 8c76686b..ccab1010 100644
--- a/src/Type/YMap.js
+++ b/src/Type/YMap.js
@@ -13,7 +13,7 @@ class YMapEvent {
 
 export default class YMap extends Type {
   _callObserver (parentSubs, remote) {
-    this._eventHandler.callEventListeners(new YMapEvent(this, parentSubs, remote))
+    this._callEventHandler(new YMapEvent(this, parentSubs, remote))
   }
   toJSON () {
     const map = {}
diff --git a/src/Type/y-xml/YXmlElement.js b/src/Type/y-xml/YXmlElement.js
index 9cc664d7..64eb7a6f 100644
--- a/src/Type/y-xml/YXmlElement.js
+++ b/src/Type/y-xml/YXmlElement.js
@@ -1,5 +1,3 @@
-/* global MutationObserver */
-
 // import diff from 'fast-diff'
 import { defaultDomFilter } from './utils.js'
 
@@ -23,12 +21,18 @@ export default class YXmlElement extends YXmlFragment {
       this._domFilter = arg2
     }
   }
+  _copy (undeleteChildren) {
+    let struct = super._copy(undeleteChildren)
+    struct.nodeName = this.nodeName
+    return struct
+  }
   _setDom (dom) {
     if (this._dom != null) {
       throw new Error('Only call this method if you know what you are doing ;)')
     } else if (dom._yxml != null) { // TODO do i need to check this? - no.. but for dev purps..
       throw new Error('Already bound to an YXml type')
     } else {
+      this._dom = dom
       dom._yxml = this
       // tag is already set in constructor
       // set attributes
@@ -43,9 +47,7 @@ export default class YXmlElement extends YXmlFragment {
         this.setAttribute(attrName, attrValue)
       }
       this.insertDomElements(0, Array.prototype.slice.call(dom.childNodes))
-      if (MutationObserver != null) {
-        this._dom = this._bindToDom(dom)
-      }
+      this._bindToDom(dom)
       return dom
     }
   }
@@ -112,6 +114,7 @@ export default class YXmlElement extends YXmlFragment {
     let dom = this._dom
     if (dom == null) {
       dom = document.createElement(this.nodeName)
+      this._dom = dom
       dom._yxml = this
       let attrs = this.getAttributes()
       for (let key in attrs) {
@@ -120,9 +123,7 @@ export default class YXmlElement extends YXmlFragment {
       this.forEach(yxml => {
         dom.appendChild(yxml.getDom())
       })
-      if (MutationObserver !== null) {
-        this._dom = this._bindToDom(dom)
-      }
+      this._bindToDom(dom)
     }
     return dom
   }
diff --git a/src/Type/y-xml/YXmlFragment.js b/src/Type/y-xml/YXmlFragment.js
index 7f6519fc..ffa3f558 100644
--- a/src/Type/y-xml/YXmlFragment.js
+++ b/src/Type/y-xml/YXmlFragment.js
@@ -1,11 +1,13 @@
 /* global MutationObserver */
 
 import { defaultDomFilter, applyChangesFromDom, reflectChangesOnDom } from './utils.js'
+import { beforeTransactionSelectionFixer, afterTransactionSelectionFixer } from './selection.js'
 
 import YArray from '../YArray.js'
 import YXmlText from './YXmlText.js'
 import YXmlEvent from './YXmlEvent.js'
 import { logID } from '../../MessageHandler/messageToString.js'
+import diff from 'fast-diff'
 
 function domToYXml (parent, doms) {
   const types = []
@@ -52,8 +54,6 @@ export default class YXmlFragment extends YArray {
         token = true
       }
     }
-    // Apply Y.Xml events to dom
-    this.observe(reflectChangesOnDom)
   }
   enableSmartScrolling (scrollElement) {
     this._scrollElement = scrollElement
@@ -68,7 +68,7 @@ export default class YXmlFragment extends YArray {
     })
   }
   _callObserver (parentSubs, remote) {
-    this._eventHandler.callEventListeners(new YXmlEvent(this, parentSubs, remote))
+    this._callEventHandler(new YXmlEvent(this, parentSubs, remote))
   }
   toString () {
     return this.map(xml => xml.toString()).join('')
@@ -111,57 +111,91 @@ export default class YXmlFragment extends YArray {
       throw new Error('Not able to bind to a DOM element, because MutationObserver is not available!')
     }
     dom.innerHTML = ''
+    this._dom = dom
+    dom._yxml = this
     this.forEach(t => {
       dom.insertBefore(t.getDom(), null)
     })
-    this._dom = dom
-    dom._yxml = this
     this._bindToDom(dom)
   }
   // binds to a dom element
   // Only call if dom and YXml are isomorph
   _bindToDom (dom) {
+    if (this._parent === null || this._parent._dom != null || typeof MutationObserver === 'undefined') {
+      // only bind if parent did not already bind
+      return
+    }
+    this._y.on('beforeTransaction', () => {
+      this._domObserverListener(this._domObserver.takeRecords())
+    })
+    this._y.on('beforeTransaction', beforeTransactionSelectionFixer)
+    this._y.on('afterTransaction', afterTransactionSelectionFixer)
+    // Apply Y.Xml events to dom
+    this.observeDeep(reflectChangesOnDom.bind(this))
+    // Apply Dom changes on Y.Xml
     this._domObserverListener = mutations => {
       this._mutualExclude(() => {
         this._y.transact(() => {
-          let diffChildren = false
+          let diffChildren = new Set()
           mutations.forEach(mutation => {
-            if (mutation.type === 'attributes') {
-              let name = mutation.attributeName
-              // check if filter accepts attribute
-              if (this._domFilter(this._dom, [name]).length > 0) {
-                var val = mutation.target.getAttribute(name)
-                if (this.getAttribute(name) !== val) {
-                  if (val == null) {
-                    this.removeAttribute(name)
-                  } else {
-                    this.setAttribute(name, val)
+            const dom = mutation.target
+            const yxml = dom._yxml
+            if (yxml == null) {
+              // dom element is filtered
+              return
+            }
+            switch (mutation.type) {
+              case 'characterData':
+                var diffs = diff(yxml.toString(), dom.nodeValue)
+                var pos = 0
+                for (var i = 0; i < diffs.length; i++) {
+                  var d = diffs[i]
+                  if (d[0] === 0) { // EQUAL
+                    pos += d[1].length
+                  } else if (d[0] === -1) { // DELETE
+                    yxml.delete(pos, d[1].length)
+                  } else { // INSERT
+                    yxml.insert(pos, d[1])
+                    pos += d[1].length
                   }
                 }
-              }
-            } else if (mutation.type === 'childList') {
-              diffChildren = true
+                break
+              case 'attributes':
+                let name = mutation.attributeName
+                // check if filter accepts attribute
+                if (this._domFilter(dom, [name]).length > 0) {
+                  var val = dom.getAttribute(name)
+                  if (yxml.getAttribute(name) !== val) {
+                    if (val == null) {
+                      yxml.removeAttribute(name)
+                    } else {
+                      yxml.setAttribute(name, val)
+                    }
+                  }
+                }
+                break
+              case 'childList':
+                diffChildren.add(mutation.target)
+                break
             }
           })
-          if (diffChildren) {
-            applyChangesFromDom(this)
+          for (let dom of diffChildren) {
+            if (dom._yxml != null) {
+              applyChangesFromDom(dom)
+            }
           }
         })
       })
     }
     this._domObserver = new MutationObserver(this._domObserverListener)
-    const observeOptions = { childList: true }
-    if (this instanceof YXmlFragment._YXmlElement) {
-      observeOptions.attributes = true
-    }
-    this._domObserver.observe(dom, observeOptions)
+    this._domObserver.observe(dom, {
+      childList: true,
+      attributes: true,
+      characterData: true,
+      subtree: true
+    })
     return dom
   }
-  _beforeChange () {
-    if (this._domObserver != null) {
-      this._domObserverListener(this._domObserver.takeRecords())
-    }
-  }
   _logString () {
     const left = this._left !== null ? this._left._lastId : null
     const origin = this._origin !== null ? this._origin._lastId : null
diff --git a/src/Type/y-xml/YXmlText.js b/src/Type/y-xml/YXmlText.js
index cff8f487..e8c48c18 100644
--- a/src/Type/y-xml/YXmlText.js
+++ b/src/Type/y-xml/YXmlText.js
@@ -1,9 +1,4 @@
-/* global MutationObserver */
-
-import diff from 'fast-diff'
 import YText from '../YText.js'
-import { getAnchorViewPosition, fixScrollPosition, getBoundingClientRect } from './utils.js'
-import { beforeTransactionSelectionFixer, afterTransactionSelectionFixer } from './selection.js'
 
 export default class YXmlText extends YText {
   constructor (arg1) {
@@ -25,6 +20,7 @@ export default class YXmlText extends YText {
     if (dom !== null) {
       this._setDom(arg1)
     }
+    /*
     var token = true
     this._mutualExclude = f => {
       if (token) {
@@ -54,11 +50,7 @@ export default class YXmlText extends YText {
         })
       }
     })
-  }
-  _integrate (y) {
-    super._integrate(y)
-    y.on('beforeTransaction', beforeTransactionSelectionFixer)
-    y.on('afterTransaction', afterTransactionSelectionFixer)
+    */
   }
   setDomFilter () {}
   enableSmartScrolling (scrollElement) {
@@ -74,42 +66,15 @@ export default class YXmlText extends YText {
     // set marker
     this._dom = dom
     dom._yxml = this
-    if (typeof MutationObserver === 'undefined') {
-      return
-    }
-    this._domObserverListener = () => {
-      this._mutualExclude(() => {
-        var diffs = diff(this.toString(), dom.nodeValue)
-        var pos = 0
-        for (var i = 0; i < diffs.length; i++) {
-          var d = diffs[i]
-          if (d[0] === 0) { // EQUAL
-            pos += d[1].length
-          } else if (d[0] === -1) { // DELETE
-            this.delete(pos, d[1].length)
-          } else { // INSERT
-            this.insert(pos, d[1])
-            pos += d[1].length
-          }
-        }
-      })
-    }
-    this._domObserver = new MutationObserver(this._domObserverListener)
-    this._domObserver.observe(this._dom, { characterData: true })
   }
   getDom () {
-    if (this._dom == null) {
+    if (this._dom === null) {
       const dom = document.createTextNode(this.toString())
       this._setDom(dom)
       return dom
     }
     return this._dom
   }
-  _beforeChange () {
-    if (this._domObserver != null && this._y !== null) { // TODO: do I need th y condition
-      this._domObserverListener(this._domObserver.takeRecords())
-    }
-  }
   _delete (y, createDelete) {
     this._unbindFromDom()
     super._delete(y, createDelete)
diff --git a/src/Type/y-xml/utils.js b/src/Type/y-xml/utils.js
index 0f035323..6c351129 100644
--- a/src/Type/y-xml/utils.js
+++ b/src/Type/y-xml/utils.js
@@ -1,3 +1,4 @@
+import YXmlText from './YXmlText.js'
 
 export function defaultDomFilter (node, attributes) {
   return attributes
@@ -81,11 +82,12 @@ function _insertNodeHelper (yxml, prevExpectedNode, child) {
  *       You can detect that a node was moved because expectedId
  *       !== actualId in the list
  */
-export function applyChangesFromDom (yxml) {
+export function applyChangesFromDom (dom) {
+  const yxml = dom._yxml
   const y = yxml._y
   let knownChildren =
     new Set(
-      Array.prototype.map.call(yxml._dom.childNodes, child => child._yxml)
+      Array.prototype.map.call(dom.childNodes, child => child._yxml)
       .filter(id => id !== undefined)
     )
   // 1. Check if any of the nodes was deleted
@@ -95,7 +97,7 @@ export function applyChangesFromDom (yxml) {
     }
   })
   // 2. iterate
-  let childNodes = yxml._dom.childNodes
+  let childNodes = dom.childNodes
   let len = childNodes.length
   let prevExpectedNode = null
   let expectedNode = iterateUntilUndeleted(yxml._start)
@@ -137,33 +139,36 @@ export function reflectChangesOnDom (event) {
   const yxml = event.target
   const dom = yxml._dom
   if (dom != null) {
-    yxml._mutualExclude(() => {
+    this._mutualExclude(() => {
       // TODO: do this once before applying stuff
       // let anchorViewPosition = getAnchorViewPosition(yxml._scrollElement)
-
-      // update attributes
-      event.attributesChanged.forEach(attributeName => {
-        const value = yxml.getAttribute(attributeName)
-        if (value === undefined) {
-          dom.removeAttribute(attributeName)
-        } else {
-          dom.setAttribute(attributeName, value)
-        }
-      })
-      if (event.childListChanged) {
-        // create fragment of undeleted nodes
-        const fragment = document.createDocumentFragment()
-        yxml.forEach(function (t) {
-          fragment.append(t.getDom())
+      if (yxml.constructor === YXmlText) {
+        yxml._dom.nodeValue = yxml.toString()
+      } else {
+        // update attributes
+        event.attributesChanged.forEach(attributeName => {
+          const value = yxml.getAttribute(attributeName)
+          if (value === undefined) {
+            dom.removeAttribute(attributeName)
+          } else {
+            dom.setAttribute(attributeName, value)
+          }
         })
-        // remove remainding nodes
-        let lastChild = dom.lastChild
-        while (lastChild !== null) {
-          dom.removeChild(lastChild)
-          lastChild = dom.lastChild
+        if (event.childListChanged) {
+          // create fragment of undeleted nodes
+          const fragment = document.createDocumentFragment()
+          yxml.forEach(function (t) {
+            fragment.append(t.getDom())
+          })
+          // remove remainding nodes
+          let lastChild = dom.lastChild
+          while (lastChild !== null) {
+            dom.removeChild(lastChild)
+            lastChild = dom.lastChild
+          }
+          // insert fragment of undeleted nodes
+          dom.append(fragment)
         }
-        // insert fragment of undeleted nodes
-        dom.append(fragment)
       }
       /* TODO: smartscrolling
       .. else if (event.type === 'childInserted' || event.type === 'insert') {
diff --git a/src/Util/EventHandler.js b/src/Util/EventHandler.js
index d92d3184..1928adac 100644
--- a/src/Util/EventHandler.js
+++ b/src/Util/EventHandler.js
@@ -20,7 +20,8 @@ export default class EventHandler {
   callEventListeners (event) {
     for (var i = 0; i < this.eventListeners.length; i++) {
       try {
-        this.eventListeners[i](event)
+        const f = this.eventListeners[i]
+        f(event)
       } catch (e) {
         /*
           Your observer threw an error. This error was caught so that Yjs
diff --git a/src/Util/UndoManager.js b/src/Util/UndoManager.js
new file mode 100644
index 00000000..aed06735
--- /dev/null
+++ b/src/Util/UndoManager.js
@@ -0,0 +1,92 @@
+import ID from './ID.js'
+
+class ReverseOperation {
+  constructor (y) {
+    const beforeState = y._transaction.beforeState
+    this.toState = new ID(y.userID, y.ss.getState(y.userID) - 1)
+    if (beforeState.has(y.userID)) {
+      this.fromState = new ID(y.userID, beforeState.get(y.userID))
+    } else {
+      this.fromState = this.toState
+    }
+    this.deletedStructs = y._transaction.deletedStructs
+  }
+}
+
+function isStructInScope (y, struct, scope) {
+  while (struct !== y) {
+    if (struct === scope) {
+      return true
+    }
+    struct = struct._parent
+  }
+  return false
+}
+
+export default class UndoManager {
+  constructor (scope) {
+    this._undoBuffer = []
+    this._redoBuffer = []
+    this._scope = scope
+    this._undoing = false
+    this._redoing = false
+    const y = scope._y
+    this.y = y
+    y.on('afterTransaction', (y, remote) => {
+      if (!remote && (y._transaction.beforeState.has(y.userID) || y._transaction.deletedStructs.size > 0)) {
+        let reverseOperation = new ReverseOperation(y)
+        if (!this._undoing) {
+          this._undoBuffer.push(reverseOperation)
+          if (!this._redoing) {
+            this._redoBuffer = []
+          }
+        } else {
+          this._redoBuffer.push(reverseOperation)
+        }
+      }
+    })
+  }
+  undo () {
+    this._undoing = true
+    this._applyReverseOperation(this._undoBuffer)
+    this._undoing = false
+  }
+  redo () {
+    this._redoing = true
+    this._applyReverseOperation(this._redoBuffer)
+    this._redoing = false
+  }
+  _applyReverseOperation (reverseBuffer) {
+    this.y.transact(() => {
+      let performedUndo = false
+      while (!performedUndo && reverseBuffer.length > 0) {
+        let undoOp = reverseBuffer.pop()
+        // make sure that it is possible to iterate {from}-{to}
+        this.y.os.getItemCleanStart(undoOp.fromState)
+        this.y.os.getItemCleanEnd(undoOp.toState)
+        this.y.os.iterate(undoOp.fromState, undoOp.toState, op => {
+          if (!op._deleted && isStructInScope(this.y, op, this._scope)) {
+            performedUndo = true
+            op._delete(this.y)
+          }
+        })
+        for (let op of undoOp.deletedStructs) {
+          if (
+            isStructInScope(this.y, op, this._scope) &&
+            op._parent !== this.y &&
+            !op._parent._deleted &&
+            (
+              op._parent._id.user !== this.y.userID ||
+              op._parent._id.clock < undoOp.fromState.clock ||
+              op._parent._id.clock > undoOp.fromState.clock
+            )
+          ) {
+            performedUndo = true
+            op = op._copy(undoOp.deletedStructs)
+            op._integrate(this.y)
+          }
+        }
+      }
+    })
+  }
+}
diff --git a/src/Y.js b/src/Y.js
index 87b4866f..746aeda9 100644
--- a/src/Y.js
+++ b/src/Y.js
@@ -4,6 +4,7 @@ import StateStore from './Store/StateStore.js'
 import { generateUserID } from './Util/generateUserID.js'
 import RootID from './Util/RootID.js'
 import NamedEventHandler from './Util/NamedEventHandler.js'
+import UndoManager from './Util/UndoManager.js'
 
 import { messageToString, messageToRoomname } from './MessageHandler/messageToString.js'
 
@@ -132,7 +133,8 @@ Y.XmlFragment = YXmlFragment
 Y.XmlText = YXmlText
 
 Y.utils = {
-  BinaryDecoder
+  BinaryDecoder,
+  UndoManager
 }
 
 Y.debug = debug