diff --git a/.eslintrc.json b/.eslintrc.json
index 2cb6635e3c1330..339e9ac6111fe4 100644
--- a/.eslintrc.json
+++ b/.eslintrc.json
@@ -63,6 +63,8 @@
 		"one-var": "off",
 		"padded-blocks": [ "error", "never" ],
 		"quote-props": [ "error", "as-needed", { "keywords": true } ],
+		"react/prop-types": "off",
+		"react/display-name": "off",
 		"semi": "error",
 		"semi-spacing": "error",
 		"space-before-blocks": [ "error", "always" ],
@@ -74,7 +76,6 @@
 				"!": true
 			}
 		} ],
-		"valid-jsdoc": [ "error", { "requireReturn": false } ],
-		"react/prop-types": "off"
+		"valid-jsdoc": [ "error", { "requireReturn": false } ]
 	}
 }
diff --git a/blocks/index.js b/blocks/index.js
index 83d496a96f7aa3..714407089947f0 100644
--- a/blocks/index.js
+++ b/blocks/index.js
@@ -7,4 +7,11 @@ export { query };
 export { default as Editable } from './components/editable';
 export { default as parse } from './parser';
 export { getCategories } from './categories';
-export { registerBlock, unregisterBlock, getBlockSettings, getBlocks } from './registration';
+export {
+	registerBlock,
+	unregisterBlock,
+	setUnknownTypeHandler,
+	getUnknownTypeHandler,
+	getBlockSettings,
+	getBlocks
+} from './registration';
diff --git a/blocks/parser.js b/blocks/parser.js
index d89ea1fddd5551..39d74c6a36b018 100644
--- a/blocks/parser.js
+++ b/blocks/parser.js
@@ -7,24 +7,26 @@ import * as query from 'hpq';
  * Internal dependencies
  */
 import { parse as grammarParse } from './post.pegjs';
-import { getBlockSettings } from './registration';
+import { getBlockSettings, getUnknownTypeHandler } from './registration';
 
 /**
  * Returns the block attributes of a registered block node given its settings.
  *
- * @param  {Object}   blockNode     Parsed block node
- * @param  {Object}   blockSettings Block settings
- * @return {Object}                 Block state, or undefined if type unknown
+ * @param  {Object} blockNode     Parsed block node
+ * @param  {Object} blockSettings Block settings
+ * @return {Object}               Block attributes
  */
 export function getBlockAttributes( blockNode, blockSettings ) {
 	const { rawContent } = blockNode;
 
 	// Merge attributes from parse with block implementation
 	let { attrs } = blockNode;
-	if ( 'function' === typeof blockSettings.attributes ) {
-		attrs = { ...attrs, ...blockSettings.attributes( rawContent ) };
-	} else if ( blockSettings.attributes ) {
-		attrs = { ...attrs, ...query.parse( rawContent, blockSettings.attributes ) };
+	if ( blockSettings ) {
+		if ( 'function' === typeof blockSettings.attributes ) {
+			attrs = { ...attrs, ...blockSettings.attributes( rawContent ) };
+		} else if ( blockSettings.attributes ) {
+			attrs = { ...attrs, ...query.parse( rawContent, blockSettings.attributes ) };
+		}
 	}
 
 	return attrs;
@@ -38,11 +40,21 @@ export function getBlockAttributes( blockNode, blockSettings ) {
  */
 export default function parse( content ) {
 	return grammarParse( content ).reduce( ( memo, blockNode ) => {
-		const settings = getBlockSettings( blockNode.blockType );
+		// Use type from block node, otherwise find unknown handler
+		let { blockType = getUnknownTypeHandler() } = blockNode;
+
+		// Try finding settings for known block type, else again fall back
+		let settings = getBlockSettings( blockType );
+		if ( ! settings ) {
+			blockType = getUnknownTypeHandler();
+			settings = getBlockSettings( blockType );
+		}
 
+		// Include in set only if settings were determined
 		if ( settings ) {
 			memo.push( {
-				blockType: blockNode.blockType,
+				blockType,
+				rawContent: blockNode.rawContent,
 				attributes: getBlockAttributes( blockNode, settings )
 			} );
 		}
diff --git a/blocks/post.pegjs b/blocks/post.pegjs
index af19f0f396a418..b77b8a82ac14b3 100644
--- a/blocks/post.pegjs
+++ b/blocks/post.pegjs
@@ -20,7 +20,6 @@ WP_Block_Html
   = ts:(!WP_Block_Balanced c:Any { return c })+
   {
     return {
-      blockType: 'html',
       attrs: {},
       rawContent: ts.join( '' )
     }
diff --git a/blocks/registration.js b/blocks/registration.js
index f3593ce9b09f8e..3dcd1f86b356c6 100644
--- a/blocks/registration.js
+++ b/blocks/registration.js
@@ -3,10 +3,17 @@
 /**
  * Block settings keyed by block slug.
  *
- * @var {Object} blocks
+ * @type {Object}
  */
 const blocks = {};
 
+/**
+ * Slug of block handling unknown types.
+ *
+ * @type {?string}
+ */
+let unknownTypeHandler;
+
 /**
  * Registers a new block provided a unique slug and an object defining its
  * behavior. Once registered, the block is made available as an option to any
@@ -60,6 +67,25 @@ export function unregisterBlock( slug ) {
 	return oldBlock;
 }
 
+/**
+ * Assigns slug of block handling unknown block types.
+ *
+ * @param {string} slug Block slug
+ */
+export function setUnknownTypeHandler( slug ) {
+	unknownTypeHandler = slug;
+}
+
+/**
+ * Retrieves slug of block handling unknown block types, or undefined if no
+ * handler has been defined.
+ *
+ * @return {?string} Blog slug
+ */
+export function getUnknownTypeHandler() {
+	return unknownTypeHandler;
+}
+
 /**
  * Returns settings associated with a registered block.
  *
diff --git a/blocks/test/parser.js b/blocks/test/parser.js
index 907489f7552e50..41dd68a5a45454 100644
--- a/blocks/test/parser.js
+++ b/blocks/test/parser.js
@@ -8,10 +8,11 @@ import { text } from 'hpq';
  * Internal dependencies
  */
 import { default as parse, getBlockAttributes } from '../parser';
-import { getBlocks, unregisterBlock, registerBlock } from '../registration';
+import { getBlocks, unregisterBlock, setUnknownTypeHandler, registerBlock } from '../registration';
 
 describe( 'block parser', () => {
-	beforeEach( () => {
+	afterEach( () => {
+		setUnknownTypeHandler( undefined );
 		getBlocks().forEach( ( block ) => {
 			unregisterBlock( block.slug );
 		} );
@@ -50,36 +51,78 @@ describe( 'block parser', () => {
 
 			const blockNode = {
 				blockType: 'core/test-block',
-				attrs: {},
+				attrs: {
+					align: 'left'
+				},
 				rawContent: '<span>Ribs <strong>& Chicken</strong></span>'
 			};
 
 			expect( getBlockAttributes( blockNode, blockSettings ) ).to.eql( {
+				align: 'left',
 				emphasis: '& Chicken'
 			} );
 		} );
+
+		it( 'should return parsed attributes for block without attributes defined', () => {
+			const blockSettings = {};
+
+			const blockNode = {
+				blockType: 'core/test-block',
+				attrs: {
+					align: 'left'
+				},
+				rawContent: '<span>Ribs <strong>& Chicken</strong></span>'
+			};
+
+			expect( getBlockAttributes( blockNode, blockSettings ) ).to.eql( {
+				align: 'left'
+			} );
+		} );
 	} );
 
 	describe( 'parse()', () => {
-		it( 'should parse the post content properly and ignore unknown blocks', () => {
-			const blockSettings = {
+		it( 'should parse the post content, ignoring unknown blocks', () => {
+			registerBlock( 'core/test-block', {
 				attributes: function( rawContent ) {
 					return {
 						content: rawContent + ' & Chicken'
 					};
 				}
-			};
-			registerBlock( 'core/test-block', blockSettings );
+			} );
 
-			const postContent = '<!-- wp:core/test-block -->Ribs<!-- /wp:core/test-block -->' +
-				'<!-- wp:core/unknown-block -->Ribs<!-- /wp:core/unknown-block -->';
+			const parsed = parse(
+				'<!-- wp:core/test-block -->Ribs<!-- /wp:core/test-block -->' +
+				'<p>Broccoli</p>' +
+				'<!-- wp:core/unknown-block -->Ribs<!-- /wp:core/unknown-block -->'
+			);
 
-			expect( parse( postContent ) ).to.eql( [ {
+			expect( parsed ).to.eql( [ {
 				blockType: 'core/test-block',
 				attributes: {
 					content: 'Ribs & Chicken'
-				}
+				},
+				rawContent: 'Ribs'
 			} ] );
 		} );
+
+		it( 'should parse the post content, using unknown block handler', () => {
+			registerBlock( 'core/test-block', {} );
+			registerBlock( 'core/unknown-block', {} );
+
+			setUnknownTypeHandler( 'core/unknown-block' );
+
+			const parsed = parse(
+				'<!-- wp:core/test-block -->Ribs<!-- /wp:core/test-block -->' +
+				'<p>Broccoli</p>' +
+				'<!-- wp:core/unknown-block -->Ribs<!-- /wp:core/unknown-block -->'
+			);
+
+			expect( parsed ).to.have.lengthOf( 3 );
+			expect( parsed.map( ( { blockType } ) => blockType ) ).to.eql( [
+				'core/test-block',
+				'core/unknown-block',
+				'core/unknown-block'
+			] );
+		} );
 	} );
 } );
diff --git a/blocks/test/registration.js b/blocks/test/registration.js
index ee6e15137c17d3..3af2d10dfe6c18 100644
--- a/blocks/test/registration.js
+++ b/blocks/test/registration.js
@@ -9,18 +9,26 @@ import sinon from 'sinon';
 /**
  * Internal dependencies
  */
-import { getBlocks, unregisterBlock, registerBlock, getBlockSettings } from '../registration';
+import {
+	registerBlock,
+	unregisterBlock,
+	setUnknownTypeHandler,
+	getUnknownTypeHandler,
+	getBlockSettings,
+	getBlocks
+} from '../registration';
 
 describe( 'blocks', () => {
 	// Reset block state before each test.
 	beforeEach( () => {
-		getBlocks().forEach( block => {
-			unregisterBlock( block.slug );
-		} );
 		sinon.stub( console, 'error' );
 	} );
 
 	afterEach( () => {
+		getBlocks().forEach( block => {
+			unregisterBlock( block.slug );
+		} );
+		setUnknownTypeHandler( undefined );
 		console.error.restore();
 	} );
 
@@ -86,6 +94,20 @@ describe( 'blocks', () => {
 		} );
 	} );
 
+	describe( 'setUnknownTypeHandler()', () => {
+		it( 'assigns unknown type handler', () => {
+			setUnknownTypeHandler( 'core/test-block' );
+
+			expect( getUnknownTypeHandler() ).to.equal( 'core/test-block' );
+		} );
+	} );
+
+	describe( 'getUnknownTypeHandler()', () => {
+		it( 'defaults to undefined', () => {
+			expect( getUnknownTypeHandler() ).to.be.undefined();
+		} );
+	} );
+
 	describe( 'getBlockSettings()', () => {
 		it( 'should return { slug } for blocks with no settings', () => {
 			registerBlock( 'core/test-block' );
diff --git a/editor/blocks/freeform/index.js b/editor/blocks/freeform/index.js
new file mode 100644
index 00000000000000..b31c419aaf2d6e
--- /dev/null
+++ b/editor/blocks/freeform/index.js
@@ -0,0 +1,23 @@
+const { html } = wp.blocks.query;
+
+wp.blocks.registerBlock( 'core/freeform', {
+	title: 'Freeform',
+
+	icon: 'text',
+
+	category: 'common',
+
+	attributes: {
+		html: html()
+	},
+
+	edit( { attributes } ) {
+		return <div contentEditable>{ attributes.html }</div>;
+	},
+
+	save( { attributes } ) {
+		return attributes.html;
+	}
+} );
+
+wp.blocks.setUnknownTypeHandler( 'core/freeform' );
diff --git a/editor/blocks/index.js b/editor/blocks/index.js
index 7319406b858f04..a31abdee56c194 100644
--- a/editor/blocks/index.js
+++ b/editor/blocks/index.js
@@ -1 +1,2 @@
+import './freeform';
 import './text';
diff --git a/editor/blocks/text/index.js b/editor/blocks/text/index.js
index 863256be4a27d4..6acb2083751216 100644
--- a/editor/blocks/text/index.js
+++ b/editor/blocks/text/index.js
@@ -10,7 +10,7 @@ wp.blocks.registerBlock( 'core/text', {
 		value: html()
 	},
 
-	edit( attributes, onChange ) {
+	edit( { attributes, onChange } ) {
 		return (
 			<Editable
 				value={ attributes.value }
@@ -19,7 +19,7 @@ wp.blocks.registerBlock( 'core/text', {
 		);
 	},
 
-	save( attributes ) {
+	save( { attributes } ) {
 		return <p>{ attributes.value }</p>;
 	}
 } );
diff --git a/editor/editor/mode/visual.js b/editor/editor/mode/visual.js
index 945783aecddae1..97346147f12800 100644
--- a/editor/editor/mode/visual.js
+++ b/editor/editor/mode/visual.js
@@ -19,13 +19,25 @@ function Blocks( { blocks, onChange } ) {
 
 	return (
 		<div className="editor-mode-visual">
-			<div>
-				{ blocks.map( ( block, index ) =>
-					<div key={ index }>
-						{ wp.blocks.getBlockSettings( block.blockType ).edit( block.attributes, onChangeBlock( index ) ) }
-					</div>
-				) }
-			</div>
+			{ blocks.map( ( block, index ) => {
+				const settings = wp.blocks.getBlockSettings( block.blockType );
+
+				let BlockEdit;
+				if ( settings ) {
+					BlockEdit = settings.edit || settings.save;
+				}
+
+				if ( ! BlockEdit ) {
+					return;
+				}
+
+				return (
+					<BlockEdit
+						key={ index }
+						attributes={ block.attributes }
+						onChange={ onChangeBlock( index ) } />
+				);
+			} ) }
 			<InserterButton />
 		</div>
 	);