diff --git a/IPython/html/nbconvert/handlers.py b/IPython/html/nbconvert/handlers.py
index f6e1094..40c820e 100644
--- a/IPython/html/nbconvert/handlers.py
+++ b/IPython/html/nbconvert/handlers.py
@@ -114,6 +114,7 @@ class NbconvertPostHandler(IPythonHandler):
         exporter = get_exporter(format, config=self.config)
         
         model = self.get_json_body()
+        name = model.get('name', 'notebook.ipynb')
         nbnode = to_notebook_json(model['content'])
         
         try:
@@ -121,7 +122,7 @@ class NbconvertPostHandler(IPythonHandler):
         except Exception as e:
             raise web.HTTPError(500, "nbconvert failed: %s" % e)
 
-        if respond_zip(self, nbnode.metadata.name, output, resources):
+        if respond_zip(self, name, output, resources):
             return
 
         # MIME type
diff --git a/IPython/html/nbconvert/tests/test_nbconvert_handlers.py b/IPython/html/nbconvert/tests/test_nbconvert_handlers.py
index ea44217..904bc98 100644
--- a/IPython/html/nbconvert/tests/test_nbconvert_handlers.py
+++ b/IPython/html/nbconvert/tests/test_nbconvert_handlers.py
@@ -10,7 +10,7 @@ import requests
 
 from IPython.html.utils import url_path_join
 from IPython.html.tests.launchnotebook import NotebookTestBase, assert_http_error
-from IPython.nbformat.current import (new_notebook, write, new_worksheet,
+from IPython.nbformat.current import (new_notebook, write,
                                       new_heading_cell, new_code_cell,
                                       new_output)
 
@@ -43,7 +43,8 @@ class NbconvertAPI(object):
 
 png_green_pixel = base64.encodestring(b'\x89PNG\r\n\x1a\n\x00\x00\x00\rIHDR\x00'
 b'\x00\x00\x01\x00\x00x00\x01\x08\x02\x00\x00\x00\x90wS\xde\x00\x00\x00\x0cIDAT'
-b'\x08\xd7c\x90\xfb\xcf\x00\x00\x02\\\x01\x1e.~d\x87\x00\x00\x00\x00IEND\xaeB`\x82')
+b'\x08\xd7c\x90\xfb\xcf\x00\x00\x02\\\x01\x1e.~d\x87\x00\x00\x00\x00IEND\xaeB`\x82'
+).decode('ascii')
 
 class APITest(NotebookTestBase):
     def setUp(self):
@@ -52,19 +53,20 @@ class APITest(NotebookTestBase):
         if not os.path.isdir(pjoin(nbdir, 'foo')):
             os.mkdir(pjoin(nbdir, 'foo'))
         
-        nb = new_notebook(name='testnb')
+        nb = new_notebook()
         
-        ws = new_worksheet()
-        nb.worksheets = [ws]
-        ws.cells.append(new_heading_cell(u'Created by test ³'))
-        cc1 = new_code_cell(input=u'print(2*6)')
-        cc1.outputs.append(new_output(output_text=u'12', output_type='stream'))
-        cc1.outputs.append(new_output(output_png=png_green_pixel, output_type='pyout'))
-        ws.cells.append(cc1)
+        nb.cells.append(new_heading_cell(u'Created by test ³'))
+        cc1 = new_code_cell(source=u'print(2*6)')
+        cc1.outputs.append(new_output(output_type="stream", data=u'12'))
+        cc1.outputs.append(new_output(output_type="execute_result",
+            mime_bundle={'image/png' : png_green_pixel},
+            prompt_number=1,
+        ))
+        nb.cells.append(cc1)
         
         with io.open(pjoin(nbdir, 'foo', 'testnb.ipynb'), 'w',
                      encoding='utf-8') as f:
-            write(nb, f, format='ipynb')
+            write(nb, f)
 
         self.nbconvert_api = NbconvertAPI(self.base_url())
 
diff --git a/IPython/html/services/contents/manager.py b/IPython/html/services/contents/manager.py
index bdff6e8..ba06072 100644
--- a/IPython/html/services/contents/manager.py
+++ b/IPython/html/services/contents/manager.py
@@ -234,8 +234,7 @@ class ContentsManager(LoggingConfigurable):
             model = {}
         if 'content' not in model and model.get('type', None) != 'directory':
             if ext == '.ipynb':
-                metadata = current.new_metadata(name=u'')
-                model['content'] = current.new_notebook(metadata=metadata)
+                model['content'] = current.new_notebook()
                 model['type'] = 'notebook'
                 model['format'] = 'json'
             else:
diff --git a/IPython/html/services/contents/tests/test_contents_api.py b/IPython/html/services/contents/tests/test_contents_api.py
index bac91de..bb5a175 100644
--- a/IPython/html/services/contents/tests/test_contents_api.py
+++ b/IPython/html/services/contents/tests/test_contents_api.py
@@ -15,7 +15,7 @@ import requests
 from IPython.html.utils import url_path_join, url_escape
 from IPython.html.tests.launchnotebook import NotebookTestBase, assert_http_error
 from IPython.nbformat import current
-from IPython.nbformat.current import (new_notebook, write, read, new_worksheet,
+from IPython.nbformat.current import (new_notebook, write, read,
                                       new_heading_cell, to_notebook_json)
 from IPython.nbformat import v2
 from IPython.utils import py3compat
@@ -142,7 +142,7 @@ class APITest(NotebookTestBase):
             # create a notebook
             with io.open(pjoin(nbdir, d, '%s.ipynb' % name), 'w',
                          encoding='utf-8') as f:
-                nb = new_notebook(name=name)
+                nb = new_notebook()
                 write(nb, f, format='ipynb')
 
             # create a text file
@@ -286,14 +286,14 @@ class APITest(NotebookTestBase):
         self.assertEqual(model['content'], '')
 
     def test_upload_untitled(self):
-        nb = new_notebook(name='Upload test')
+        nb = new_notebook()
         nbmodel = {'content': nb, 'type': 'notebook'}
         resp = self.api.upload_untitled(path=u'å b',
                                               body=json.dumps(nbmodel))
         self._check_created(resp, 'Untitled0.ipynb', u'å b')
 
     def test_upload(self):
-        nb = new_notebook(name=u'ignored')
+        nb = new_notebook()
         nbmodel = {'content': nb, 'type': 'notebook'}
         resp = self.api.upload(u'Upload tést.ipynb', path=u'å b',
                                               body=json.dumps(nbmodel))
@@ -355,7 +355,6 @@ class APITest(NotebookTestBase):
         resp = self.api.read(u'Upload tést.ipynb', u'å b')
         data = resp.json()
         self.assertEqual(data['content']['nbformat'], current.nbformat)
-        self.assertEqual(data['content']['orig_nbformat'], 2)
 
     def test_copy_untitled(self):
         resp = self.api.copy_untitled(u'ç d.ipynb', path=u'å b')
@@ -416,9 +415,7 @@ class APITest(NotebookTestBase):
         resp = self.api.read('a.ipynb', 'foo')
         nbcontent = json.loads(resp.text)['content']
         nb = to_notebook_json(nbcontent)
-        ws = new_worksheet()
-        nb.worksheets = [ws]
-        ws.cells.append(new_heading_cell(u'Created by test ³'))
+        nb.cells.append(new_heading_cell(u'Created by test ³'))
 
         nbmodel= {'name': 'a.ipynb', 'path':'foo', 'content': nb, 'type': 'notebook'}
         resp = self.api.save('a.ipynb', path='foo', body=json.dumps(nbmodel))
@@ -426,11 +423,11 @@ class APITest(NotebookTestBase):
         nbfile = pjoin(self.notebook_dir.name, 'foo', 'a.ipynb')
         with io.open(nbfile, 'r', encoding='utf-8') as f:
             newnb = read(f, format='ipynb')
-        self.assertEqual(newnb.worksheets[0].cells[0].source,
+        self.assertEqual(newnb.cells[0].source,
                          u'Created by test ³')
         nbcontent = self.api.read('a.ipynb', 'foo').json()['content']
         newnb = to_notebook_json(nbcontent)
-        self.assertEqual(newnb.worksheets[0].cells[0].source,
+        self.assertEqual(newnb.cells[0].source,
                          u'Created by test ³')
 
         # Save and rename
@@ -455,10 +452,8 @@ class APITest(NotebookTestBase):
         # Modify it
         nbcontent = json.loads(resp.text)['content']
         nb = to_notebook_json(nbcontent)
-        ws = new_worksheet()
-        nb.worksheets = [ws]
         hcell = new_heading_cell('Created by test')
-        ws.cells.append(hcell)
+        nb.cells.append(hcell)
         # Save
         nbmodel= {'name': 'a.ipynb', 'path':'foo', 'content': nb, 'type': 'notebook'}
         resp = self.api.save('a.ipynb', path='foo', body=json.dumps(nbmodel))
@@ -469,14 +464,14 @@ class APITest(NotebookTestBase):
 
         nbcontent = self.api.read('a.ipynb', 'foo').json()['content']
         nb = to_notebook_json(nbcontent)
-        self.assertEqual(nb.worksheets[0].cells[0].source, 'Created by test')
+        self.assertEqual(nb.cells[0].source, 'Created by test')
 
         # Restore cp1
         r = self.api.restore_checkpoint('a.ipynb', 'foo', cp1['id'])
         self.assertEqual(r.status_code, 204)
         nbcontent = self.api.read('a.ipynb', 'foo').json()['content']
         nb = to_notebook_json(nbcontent)
-        self.assertEqual(nb.worksheets, [])
+        self.assertEqual(nb.cells, [])
 
         # Delete cp1
         r = self.api.delete_checkpoint('a.ipynb', 'foo', cp1['id'])
diff --git a/IPython/html/services/contents/tests/test_manager.py b/IPython/html/services/contents/tests/test_manager.py
index d5dfff4..558f73a 100644
--- a/IPython/html/services/contents/tests/test_manager.py
+++ b/IPython/html/services/contents/tests/test_manager.py
@@ -95,11 +95,9 @@ class TestContentsManager(TestCase):
         return os_path
 
     def add_code_cell(self, nb):
-        output = current.new_output("display_data", output_javascript="alert('hi');")
+        output = current.new_output("display_data", {'application/javascript': "alert('hi');"})
         cell = current.new_code_cell("print('hi')", outputs=[output])
-        if not nb.worksheets:
-            nb.worksheets.append(current.new_worksheet())
-        nb.worksheets[0].cells.append(cell)
+        nb.cells.append(cell)
 
     def new_notebook(self):
         cm = self.contents_manager
@@ -309,13 +307,13 @@ class TestContentsManager(TestCase):
         nb, name, path = self.new_notebook()
 
         cm.mark_trusted_cells(nb, name, path)
-        for cell in nb.worksheets[0].cells:
+        for cell in nb.cells:
             if cell.cell_type == 'code':
                 assert not cell.metadata.trusted
 
         cm.trust_notebook(name, path)
         nb = cm.get_model(name, path)['content']
-        for cell in nb.worksheets[0].cells:
+        for cell in nb.cells:
             if cell.cell_type == 'code':
                 assert cell.metadata.trusted
 
diff --git a/IPython/html/services/sessions/tests/test_sessions_api.py b/IPython/html/services/sessions/tests/test_sessions_api.py
index 9623415..643fd68 100644
--- a/IPython/html/services/sessions/tests/test_sessions_api.py
+++ b/IPython/html/services/sessions/tests/test_sessions_api.py
@@ -62,7 +62,7 @@ class SessionAPITest(NotebookTestBase):
 
         with io.open(pjoin(nbdir, 'foo', 'nb1.ipynb'), 'w',
                      encoding='utf-8') as f:
-            nb = new_notebook(name='nb1')
+            nb = new_notebook()
             write(nb, f, format='ipynb')
 
         self.sess_api = SessionAPI(self.base_url())
diff --git a/IPython/html/static/notebook/js/codecell.js b/IPython/html/static/notebook/js/codecell.js
index c6d19c8..ca5b6f3 100644
--- a/IPython/html/static/notebook/js/codecell.js
+++ b/IPython/html/static/notebook/js/codecell.js
@@ -382,13 +382,11 @@ define([
 
 
     CodeCell.prototype.collapse_output = function () {
-        this.collapsed = true;
         this.output_area.collapse();
     };
 
 
     CodeCell.prototype.expand_output = function () {
-        this.collapsed = false;
         this.output_area.expand();
         this.output_area.unscroll_area();
     };
@@ -399,7 +397,6 @@ define([
     };
 
     CodeCell.prototype.toggle_output = function () {
-        this.collapsed = Boolean(1 - this.collapsed);
         this.output_area.toggle_output();
     };
 
@@ -467,22 +464,18 @@ define([
     CodeCell.prototype.fromJSON = function (data) {
         Cell.prototype.fromJSON.apply(this, arguments);
         if (data.cell_type === 'code') {
-            if (data.input !== undefined) {
-                this.set_text(data.input);
+            if (data.source !== undefined) {
+                this.set_text(data.source);
                 // make this value the starting point, so that we can only undo
                 // to this state, instead of a blank cell
                 this.code_mirror.clearHistory();
                 this.auto_highlight();
             }
-            if (data.prompt_number !== undefined) {
-                this.set_input_prompt(data.prompt_number);
-            } else {
-                this.set_input_prompt();
-            }
+            this.set_input_prompt(data.prompt_number);
             this.output_area.trusted = data.metadata.trusted || false;
             this.output_area.fromJSON(data.outputs);
-            if (data.collapsed !== undefined) {
-                if (data.collapsed) {
+            if (data.metadata.collapsed !== undefined) {
+                if (data.metadata.collapsed) {
                     this.collapse_output();
                 } else {
                     this.expand_output();
@@ -494,16 +487,17 @@ define([
 
     CodeCell.prototype.toJSON = function () {
         var data = Cell.prototype.toJSON.apply(this);
-        data.input = this.get_text();
+        data.source = this.get_text();
         // is finite protect against undefined and '*' value
         if (isFinite(this.input_prompt_number)) {
             data.prompt_number = this.input_prompt_number;
+        } else {
+            data.prompt_number = null;
         }
         var outputs = this.output_area.toJSON();
         data.outputs = outputs;
-        data.language = 'python';
         data.metadata.trusted = this.output_area.trusted;
-        data.collapsed = this.output_area.collapsed;
+        data.metadata.collapsed = this.output_area.collapsed;
         return data;
     };
 
diff --git a/IPython/html/static/notebook/js/notebook.js b/IPython/html/static/notebook/js/notebook.js
index 8181138..98c6111 100644
--- a/IPython/html/static/notebook/js/notebook.js
+++ b/IPython/html/static/notebook/js/notebook.js
@@ -121,10 +121,8 @@ define([
         this.autosave_timer = null;
         // autosave *at most* every two minutes
         this.minimum_autosave_interval = 120000;
-        // single worksheet for now
-        this.worksheet_metadata = {};
         this.notebook_name_blacklist_re = /[\/\\:]/;
-        this.nbformat = 3; // Increment this when changing the nbformat
+        this.nbformat = 4; // Increment this when changing the nbformat
         this.nbformat_minor = 0; // Increment this when changing the nbformat
         this.codemirror_mode = 'ipython';
         this.create_elements();
@@ -1785,8 +1783,6 @@ define([
     /**
      * Load a notebook from JSON (.ipynb).
      * 
-     * This currently handles one worksheet: others are deleted.
-     * 
      * @method fromJSON
      * @param {Object} data JSON representation of a notebook
      */
@@ -1818,50 +1814,22 @@ define([
             this.set_codemirror_mode(cm_mode);
         }
         
-        // Only handle 1 worksheet for now.
-        var worksheet = content.worksheets[0];
-        if (worksheet !== undefined) {
-            if (worksheet.metadata) {
-                this.worksheet_metadata = worksheet.metadata;
-            }
-            var new_cells = worksheet.cells;
-            ncells = new_cells.length;
-            var cell_data = null;
-            var new_cell = null;
-            for (i=0; i<ncells; i++) {
-                cell_data = new_cells[i];
-                // VERSIONHACK: plaintext -> raw
-                // handle never-released plaintext name for raw cells
-                if (cell_data.cell_type === 'plaintext'){
-                    cell_data.cell_type = 'raw';
-                }
-
-                new_cell = this.insert_cell_at_index(cell_data.cell_type, i);
-                new_cell.fromJSON(cell_data);
-                if (new_cell.cell_type == 'code' && !new_cell.output_area.trusted) {
-                    trusted = false;
-                }
+        var new_cells = content.cells;
+        ncells = new_cells.length;
+        var cell_data = null;
+        var new_cell = null;
+        for (i=0; i<ncells; i++) {
+            cell_data = new_cells[i];
+            new_cell = this.insert_cell_at_index(cell_data.cell_type, i);
+            new_cell.fromJSON(cell_data);
+            if (new_cell.cell_type == 'code' && !new_cell.output_area.trusted) {
+                trusted = false;
             }
         }
         if (trusted !== this.trusted) {
             this.trusted = trusted;
             this.events.trigger("trust_changed.Notebook", trusted);
         }
-        if (content.worksheets.length > 1) {
-            dialog.modal({
-                notebook: this,
-                keyboard_manager: this.keyboard_manager,
-                title : "Multiple worksheets",
-                body : "This notebook has " + data.worksheets.length + " worksheets, " +
-                    "but this version of IPython can only handle the first.  " +
-                    "If you save this notebook, worksheets after the first will be lost.",
-                buttons : {
-                    OK : {
-                        class : "btn-danger"
-                    }
-                }
-            });
-        }
     };
 
     /**
@@ -1871,6 +1839,10 @@ define([
      * @return {Object} A JSON-friendly representation of this notebook.
      */
     Notebook.prototype.toJSON = function () {
+        // remove the conversion indicator, which only belongs in-memory
+        delete this.metadata.orig_nbformat;
+        delete this.metadata.orig_nbformat_minor;
+
         var cells = this.get_cells();
         var ncells = cells.length;
         var cell_array = new Array(ncells);
@@ -1883,11 +1855,7 @@ define([
             cell_array[i] = cell.toJSON();
         }
         var data = {
-            // Only handle 1 worksheet for now.
-            worksheets : [{
-                cells: cell_array,
-                metadata: this.worksheet_metadata
-            }],
+            cells: cell_array,
             metadata : this.metadata
         };
         if (trusted != this.trusted) {
@@ -2337,10 +2305,13 @@ define([
         }
         this.set_dirty(false);
         this.scroll_to_top();
-        if (data.orig_nbformat !== undefined && data.nbformat !== data.orig_nbformat) {
+        var nbmodel = data.content;
+        var orig_nbformat = nbmodel.metadata.orig_nbformat;
+        var orig_nbformat_minor = nbmodel.metadata.orig_nbformat_minor;
+        if (orig_nbformat !== undefined && nbmodel.nbformat !== orig_nbformat) {
             var msg = "This notebook has been converted from an older " +
-            "notebook format (v"+data.orig_nbformat+") to the current notebook " +
-            "format (v"+data.nbformat+"). The next time you save this notebook, the " +
+            "notebook format (v"+orig_nbformat+") to the current notebook " +
+            "format (v"+nbmodel.nbformat+"). The next time you save this notebook, the " +
             "newer notebook format will be used and older versions of IPython " +
             "may not be able to read it. To keep the older version, close the " +
             "notebook without saving it.";
@@ -2355,10 +2326,10 @@ define([
                     }
                 }
             });
-        } else if (data.orig_nbformat_minor !== undefined && data.nbformat_minor !== data.orig_nbformat_minor) {
+        } else if (orig_nbformat_minor !== undefined && nbmodel.nbformat_minor !== orig_nbformat_minor) {
             var that = this;
-            var orig_vs = 'v' + data.nbformat + '.' + data.orig_nbformat_minor;
-            var this_vs = 'v' + data.nbformat + '.' + this.nbformat_minor;
+            var orig_vs = 'v' + nbmodel.nbformat + '.' + orig_nbformat_minor;
+            var this_vs = 'v' + nbmodel.nbformat + '.' + this.nbformat_minor;
             var msg = "This notebook is version " + orig_vs + ", but we only fully support up to " +
             this_vs + ".  You can still work with this notebook, but some features " +
             "introduced in later notebook versions may not be available.";
diff --git a/IPython/html/static/notebook/js/outputarea.js b/IPython/html/static/notebook/js/outputarea.js
index 3be41f5..3732563 100644
--- a/IPython/html/static/notebook/js/outputarea.js
+++ b/IPython/html/static/notebook/js/outputarea.js
@@ -211,7 +211,7 @@ define([
         var content = msg.content;
         if (msg_type === "stream") {
             json.text = content.text;
-            json.stream = content.name;
+            json.name = content.name;
         } else if (msg_type === "display_data") {
             json = content.data;
             json.output_type = msg_type;
@@ -234,6 +234,7 @@ define([
     
     
     OutputArea.prototype.rename_keys = function (data, key_map) {
+        // TODO: This is now unused, should it be removed?
         var remapped = {};
         for (var key in data) {
             var new_key = key_map[key] || key;
@@ -260,7 +261,10 @@ define([
         // TODO: right now everything is a string, but JSON really shouldn't be.
         // nbformat 4 will fix that.
         $.map(OutputArea.output_types, function(key){
-            if (json[key] !== undefined && typeof json[key] !== 'string') {
+            if (key !== 'application/json' &&
+                json[key] !== undefined &&
+                typeof json[key] !== 'string'
+            ) {
                 console.log("Invalid type for " + key, json[key]);
                 delete json[key];
             }
@@ -449,23 +453,18 @@ define([
 
 
     OutputArea.prototype.append_stream = function (json) {
-        // temporary fix: if stream undefined (json file written prior to this patch),
-        // default to most likely stdout:
-        if (json.stream === undefined){
-            json.stream = 'stdout';
-        }
-        var text = json.text;
-        var subclass = "output_"+json.stream;
+        var text = json.data;
+        var subclass = "output_"+json.name;
         if (this.outputs.length > 0){
             // have at least one output to consider
             var last = this.outputs[this.outputs.length-1];
-            if (last.output_type == 'stream' && json.stream == last.stream){
+            if (last.output_type == 'stream' && json.name == last.name){
                 // latest output was in the same stream,
                 // so append directly into its pre tag
                 // escape ANSI & HTML specials:
-                last.text = utils.fixCarriageReturn(last.text + json.text);
+                last.data = utils.fixCarriageReturn(last.data + json.data);
                 var pre = this.element.find('div.'+subclass).last().find('pre');
-                var html = utils.fixConsole(last.text);
+                var html = utils.fixConsole(last.data);
                 // The only user content injected with this HTML call is
                 // escaped by the fixConsole() method.
                 pre.html(html);
@@ -852,70 +851,33 @@ define([
 
     // JSON serialization
 
-    OutputArea.prototype.fromJSON = function (outputs) {
+    OutputArea.prototype.fromJSON = function (outputs, metadata) {
         var len = outputs.length;
-        var data;
+        metadata = metadata || {};
 
         for (var i=0; i<len; i++) {
-            data = outputs[i];
-            var msg_type = data.output_type;
-            if (msg_type == "pyout") {
-                // pyout message has been renamed to execute_result,
-                // but the nbformat has not been updated,
-                // so transform back to pyout for json.
-                msg_type = data.output_type = "execute_result";
-            } else if (msg_type == "pyerr") {
-                // pyerr message has been renamed to error,
-                // but the nbformat has not been updated,
-                // so transform back to pyerr for json.
-                msg_type = data.output_type = "error";
+            this.append_output(outputs[i]);
+        }
+
+        if (metadata.collapsed !== undefined) {
+            this.collapsed = metadata.collapsed;
+            if (metadata.collapsed) {
+                this.collapse_output();
             }
-            if (msg_type === "display_data" || msg_type === "execute_result") {
-                // convert short keys to mime keys
-                // TODO: remove mapping of short keys when we update to nbformat 4
-                 data = this.rename_keys(data, OutputArea.mime_map_r);
-                 data.metadata = this.rename_keys(data.metadata, OutputArea.mime_map_r);
-                 // msg spec JSON is an object, nbformat v3 JSON is a JSON string
-                 if (data["application/json"] !== undefined && typeof data["application/json"] === 'string') {
-                     data["application/json"] = JSON.parse(data["application/json"]);
-                 }
+        }
+        if (metadata.autoscroll !== undefined) {
+            this.collapsed = metadata.collapsed;
+            if (metadata.collapsed) {
+                this.collapse_output();
+            } else {
+                this.expand_output();
             }
-            
-            this.append_output(data);
         }
     };
 
 
     OutputArea.prototype.toJSON = function () {
-        var outputs = [];
-        var len = this.outputs.length;
-        var data;
-        for (var i=0; i<len; i++) {
-            data = this.outputs[i];
-            var msg_type = data.output_type;
-            if (msg_type === "display_data" || msg_type === "execute_result") {
-                  // convert mime keys to short keys
-                 data = this.rename_keys(data, OutputArea.mime_map);
-                 data.metadata = this.rename_keys(data.metadata, OutputArea.mime_map);
-                 // msg spec JSON is an object, nbformat v3 JSON is a JSON string
-                 if (data.json !== undefined && typeof data.json !== 'string') {
-                     data.json = JSON.stringify(data.json);
-                 }
-            }
-            if (msg_type == "execute_result") {
-                // pyout message has been renamed to execute_result,
-                // but the nbformat has not been updated,
-                // so transform back to pyout for json.
-                data.output_type = "pyout";
-            } else if (msg_type == "error") {
-                // pyerr message has been renamed to error,
-                // but the nbformat has not been updated,
-                // so transform back to pyerr for json.
-                data.output_type = "pyerr";
-            }
-            outputs[i] = data;
-        }
-        return outputs;
+        return this.outputs;
     };
 
     /**
@@ -948,29 +910,6 @@ define([
     OutputArea.minimum_scroll_threshold = 20;
 
 
-
-    OutputArea.mime_map = {
-        "text/plain" : "text",
-        "text/html" : "html",
-        "image/svg+xml" : "svg",
-        "image/png" : "png",
-        "image/jpeg" : "jpeg",
-        "text/latex" : "latex",
-        "application/json" : "json",
-        "application/javascript" : "javascript",
-    };
-
-    OutputArea.mime_map_r = {
-        "text" : "text/plain",
-        "html" : "text/html",
-        "svg" : "image/svg+xml",
-        "png" : "image/png",
-        "jpeg" : "image/jpeg",
-        "latex" : "text/latex",
-        "json" : "application/json",
-        "javascript" : "application/javascript",
-    };
-
     OutputArea.display_order = [
         'application/javascript',
         'text/html',
diff --git a/IPython/html/tests/notebook/output.js b/IPython/html/tests/notebook/output.js
index 1fcfe44..b519b64 100644
--- a/IPython/html/tests/notebook/output.js
+++ b/IPython/html/tests/notebook/output.js
@@ -29,7 +29,7 @@ casper.notebook_test(function () {
                 var ex = expected[i];
                 this.test.assertEquals(r.output_type, ex.output_type, "output  " + i);
                 if (r.output_type === 'stream') {
-                    this.test.assertEquals(r.stream, ex.stream, "stream  " + i);
+                    this.test.assertEquals(r.name, ex.name, "stream  " + i);
                     this.test.assertEquals(r.text, ex.text, "content " + i);
                 }
             }
@@ -57,7 +57,7 @@ casper.notebook_test(function () {
         "print(3)"
         ].join("\n"), [{
             output_type: "stream",
-            stream: "stdout",
+            name: "stdout",
             text: "1\n2\n3\n"
         }]
     );
@@ -69,11 +69,11 @@ casper.notebook_test(function () {
         "print(3, file=sys.stderr)"
         ].join("\n"), [{
             output_type: "stream",
-            stream: "stdout",
+            name: "stdout",
             text: "1\n2\n"
         },{
             output_type: "stream",
-            stream: "stderr",
+            name: "stderr",
             text: "3\n"
         }]
     );
@@ -85,13 +85,13 @@ casper.notebook_test(function () {
         "print(3)"
         ].join("\n"), [{
             output_type: "stream",
-            stream: "stdout",
+            name: "stdout",
             text: "1\n"
         },{
             output_type: "display_data",
         },{
             output_type: "stream",
-            stream: "stdout",
+            name: "stdout",
             text: "3\n"
         }]
     );
diff --git a/IPython/html/tests/notebook/roundtrip.js b/IPython/html/tests/notebook/roundtrip.js
index 38ef881..a243784 100644
--- a/IPython/html/tests/notebook/roundtrip.js
+++ b/IPython/html/tests/notebook/roundtrip.js
@@ -14,7 +14,7 @@ mime =  {
         "json" : "application/json",
         "javascript" : "application/javascript",
     };
-    
+
 var black_dot_jpeg="u\"\"\"/9j/4AAQSkZJRgABAQEASABIAAD/2wBDACodICUgGiolIiUvLSoyP2lEPzo6P4FcYUxpmYagnpaG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\nEH//2Q==\"\"\"";
 var black_dot_png = 'u\"iVBORw0KGgoAAAANSUhEUgAAAAEAAAABAQMAAAAl21bKAAAAA1BMVEUAAACnej3aAAAAAWJLR0QA\\niAUdSAAAAAlwSFlzAAALEwAACxMBAJqcGAAAAAd0SU1FB94BCRQnOqNu0b4AAAAKSURBVAjXY2AA\\nAAACAAHiIbwzAAAAAElFTkSuQmCC\"';
 var svg = "\"<svg width='1cm' height='1cm' viewBox='0 0 1000 500'><defs><style>rect {fill:red;}; </style></defs><rect id='r1' x='200' y='100' width='600' height='300' /></svg>\"";
@@ -24,8 +24,10 @@ var svg = "\"<svg width='1cm' height='1cm' viewBox='0 0 1000 500'><defs><style>r
 // name, and that fromJSON also gets its long mimetype name
 function assert_has(short_name, json, result, result2) {
     long_name = mime[short_name];
-    this.test.assertTrue(json[0].hasOwnProperty(short_name),
-            'toJSON()   representation uses ' + short_name);
+    this.test.assertFalse(json[0].hasOwnProperty(short_name),
+            "toJSON()   representation doesn't use " + short_name);
+    this.test.assertTrue(json[0].hasOwnProperty(long_name),
+            'toJSON()   representation uses ' + long_name);
     this.test.assertTrue(result.hasOwnProperty(long_name),
             'toJSON()   original embedded JSON keeps ' + long_name);
     this.test.assertTrue(result2.hasOwnProperty(long_name),
@@ -34,8 +36,8 @@ function assert_has(short_name, json, result, result2) {
           
 // helper function for checkout that the first two cells have a particular
 // output_type (either 'execute_result' or 'display_data'), and checks the to/fromJSON
-// for a set of mimetype keys, using their short names ('javascript', 'text',
-// 'png', etc).
+// for a set of mimetype keys, ensuring the old short names ('javascript', 'text',
+// 'png', etc) are not used.
 function check_output_area(output_type, keys) {
     this.wait_for_output(0);
     json = this.evaluate(function() {
diff --git a/IPython/html/tests/test_files.py b/IPython/html/tests/test_files.py
index 3328212..b891618 100644
--- a/IPython/html/tests/test_files.py
+++ b/IPython/html/tests/test_files.py
@@ -10,8 +10,8 @@ pjoin = os.path.join
 import requests
 import json
 
-from IPython.nbformat.current import (new_notebook, write, new_worksheet,
-                              new_heading_cell, new_code_cell,
+from IPython.nbformat.current import (new_notebook, write,
+                              new_markdown_cell, new_code_cell,
                               new_output)
 
 from IPython.html.utils import url_path_join
@@ -62,18 +62,18 @@ class FilesTest(NotebookTestBase):
         nbdir = self.notebook_dir.name
         base = self.base_url()
 
-        nb = new_notebook(name='testnb')
-        
-        ws = new_worksheet()
-        nb.worksheets = [ws]
-        ws.cells.append(new_heading_cell(u'Created by test ³'))
-        cc1 = new_code_cell(input=u'print(2*6)')
-        cc1.outputs.append(new_output(output_text=u'12', output_type='stream'))
-        ws.cells.append(cc1)
+        nb = new_notebook(
+            cells=[
+                new_markdown_cell(u'Created by test ³'),
+                new_code_cell("print(2*6)", outputs=[
+                    new_output("stream", text="12"),
+                ])
+            ]
+        )
 
         with io.open(pjoin(nbdir, 'testnb.ipynb'), 'w', 
             encoding='utf-8') as f:
-            write(nb, f, format='ipynb')
+            write(nb, f)
 
         with io.open(pjoin(nbdir, 'test.bin'), 'wb') as f:
             f.write(b'\xff' + os.urandom(5))