diff --git a/api/document/js/Api.ts b/api/document/js/Api.ts
index 07d84ad5a..1eb45a14c 100644
--- a/api/document/js/Api.ts
+++ b/api/document/js/Api.ts
@@ -36,6 +36,7 @@ export interface ApiContent {
   inlines: ApiContent[];
   text: string;
   footnote_node?: ApiNode;
+  href?: string;
 }
 
 export class Api<T> {
diff --git a/api/document/js/__tests__/Api.test.ts b/api/document/js/__tests__/Api.test.ts
index 6f590f539..ccb6dfd73 100644
--- a/api/document/js/__tests__/Api.test.ts
+++ b/api/document/js/__tests__/Api.test.ts
@@ -23,6 +23,7 @@ const api = new Api<string>({
 });
 
 describe('fetch()', () => {
+  axios.get = jest.fn(async () => ({ data: '' }));
   it('passes the correct args', () => {
     api.fetch();
     expect(axios.get).toHaveBeenCalledWith(
diff --git a/api/document/js/__tests__/menu.test.ts b/api/document/js/__tests__/menu.test.ts
index 83d2324b6..5a68592c3 100644
--- a/api/document/js/__tests__/menu.test.ts
+++ b/api/document/js/__tests__/menu.test.ts
@@ -21,6 +21,7 @@ describe('menu', () => {
       'Undo last change',
       'Redo last undone change',
       'Append paragraph',
+      'Add or remove link',
       'Append bullet list',
       'Append ordered list',
       'Outdent list',
diff --git a/api/document/js/__tests__/parse-doc.test.ts b/api/document/js/__tests__/parse-doc.test.ts
index 4f3e305c0..444674d51 100644
--- a/api/document/js/__tests__/parse-doc.test.ts
+++ b/api/document/js/__tests__/parse-doc.test.ts
@@ -1,6 +1,6 @@
 import axios from 'axios';
 
-import { ApiContent } from '../Api';
+import { ApiContent, ApiNode } from '../Api';
 import parseDoc, { convertContent } from '../parse-doc';
 import { apiFactory } from '../serialize-doc';
 import schema from '../schema';
@@ -117,6 +117,54 @@ describe('parseDoc()', () => {
     expect(lis[1].content.child(1).type.name).toBe('para');
   });
 
+  it('loads links', () => {
+    // This checks link parsing but doesn't check any of the interaction
+    // involved, such as making sure a prompt actually pops up in response
+    // to a button click.
+    const node: ApiNode = {
+      node_type: 'para',
+      content: [
+        {
+          content_type: '__text__',
+          text: 'Initial ',
+          inlines: [],
+        },
+        {
+          content_type: 'external_link',
+          href: 'http://example.org',
+          text: 'content.',
+          inlines: [{ content_type: '__text__', text: 'content.', inlines: [] }],
+        },
+
+      ],
+      children: [],
+    };
+
+    const result = parseDoc(node); // The top-level node.
+    expect(result.type.name).toBe('para'); 
+    expect(result.content.size).toEqual('Initial content.'.length + 2); // Node boundaries add two.
+    expect(result.childCount).toEqual(1); // One inner node.
+
+    const paraText = result.child(0); // The inner paraText node.
+    expect(paraText.content.size).toEqual('Initial content.'.length);
+    expect(paraText.type.name).toEqual('paraText');
+    expect(paraText.childCount).toEqual(2); // The two inline children of the inner node.
+
+    const plainText = paraText.child(0); // The first inline child, plain text.
+    expect(plainText.type.name).toEqual('text');
+    expect(plainText.text).toEqual('Initial ');
+
+    const externalLink = paraText.child(1); // The second inline child, containing the link.
+    expect(externalLink.type.name).toEqual('text');
+    expect(externalLink.text).toEqual('content.');
+    expect(externalLink.marks.length).toEqual(1); // Just one link.
+
+    const mark = externalLink.marks[0]; // The link markup.
+    expect(mark.type.name).toEqual('external_link');
+    expect(mark.attrs.href).toEqual('http://example.org');
+
+  });
+
   describe('unimplementedNode', () => {
     it('saves original data', () => {
       const node = {
diff --git a/api/document/js/menu.ts b/api/document/js/menu.ts
index b3e0098cf..89404176c 100644
--- a/api/document/js/menu.ts
+++ b/api/document/js/menu.ts
@@ -1,3 +1,4 @@
+import { toggleMark } from 'prosemirror-commands';
 import { menuBar, undoItem, redoItem, MenuItem, MenuItemSpec } from 'prosemirror-menu';
 
 import { JsonApi } from './Api';
@@ -11,6 +12,7 @@ import {
   outdentLi,
 } from './commands';
 import icons from './icons';
+import schema from './schema';
 
 function makeButton(content) {
   return new MenuItem({
@@ -33,13 +35,14 @@ export default function menu(api: JsonApi) {
         // prosemirror-menu. For more details, see:
         //
         // https://github.com/ProseMirror/prosemirror-menu/issues/12
-        undoItem as any as MenuItem,
-        redoItem as any as MenuItem,
+        undoItem as any as MenuItem, // title: 'Undo last change'
+        redoItem as any as MenuItem, // title: 'Redo last undone change'
         makeButton({
           label: 'P',
           run: appendParagraphNear,
           title: 'Append paragraph',
         }),
+        linkItem(schema.marks.external_link), // title: 'Add or remove link'
         makeButton({
           icon: icons.newBulletList,
           run: appendBulletListNear,
@@ -69,10 +72,47 @@ export default function menu(api: JsonApi) {
         }),
         makeButton({
           label: 'Save then XML',
-          title: 'Save document then edit as XML',
           run: makeSaveThenXml(api),
+          title: 'Save document then edit as XML',
         }),
       ],
     ],
   });
 }
+
+function markActive(state, type) {
+  const { from, $from, to, empty } = state.selection;
+  if (empty) {
+    return type.isInSet(state.storedMarks || $from.marks());
+  }
+  return state.doc.rangeHasMark(from, to, type);
+}
+
+function externalLink(state, dispatch, view, markType) {
+  // This function might belong in ./commands
+  if (markActive(state, markType)) {
+    toggleMark(markType)(state, dispatch);
+    return true;
+  }
+  // We need a replacement for prompt here.
+  toggleMark(schema.marks.external_link, {
+    href: prompt('URL', 'URL: '),
+  })(view.state, view.dispatch);
+  view.focus();
+  return true;
+}
+
+function linkItem(markType) {
+  return new MenuItem({
+    class: 'menuitem-clickable',
+    // These defaults are needed due to a doc issue. See
+    // https://github.com/ProseMirror/prosemirror-menu/issues/15
+    css: '',
+    execEvent: 'mousedown',
+    title: 'Add or remove link',
+    label: 'A',
+    active(state) { return markActive(state, markType); },
+    enable(state) { return !state.selection.empty; },
+    run(state, dispatch, view) { return externalLink(state, dispatch, view, markType); },
+  });
+}
diff --git a/api/document/js/parse-doc.ts b/api/document/js/parse-doc.ts
index b8c121910..643034e51 100644
--- a/api/document/js/parse-doc.ts
+++ b/api/document/js/parse-doc.ts
@@ -101,4 +101,5 @@ const NODE_TYPE_CONVERTERS: NodeConverterMap = {
 
 const CONTENT_TYPE_CONVERTERS = {
   unimplementedMark: content => factory.unimplementedMark(content),
+  external_link: content => factory.external_link(content.href),
 };
diff --git a/api/document/js/schema.ts b/api/document/js/schema.ts
index 2c5cce174..84c3b743a 100644
--- a/api/document/js/schema.ts
+++ b/api/document/js/schema.ts
@@ -79,17 +79,25 @@ const schema = new Schema({
       },
       toDOM(node) {
         const nodeType = node.attrs.data.node_type || '[no-node-type]';
-        return ['div', { class: 'unimplemented' }, nodeType];
+        return ['div', { class: 'unimplemented whatever' }, nodeType];
       },
     },
     ...listSchemaNodes,
   },
   marks: {
+    external_link: {
+      attrs: {
+        href: {},
+      },
+      toDOM(data) {
+        return ['a', { class: `external-link`, href: data.attrs.href }];
+      },
+    },
     unimplementedMark: {
       attrs: {
         data: {}, // will hold unrendered content
       },
-      toDOM: () => ['span', { class: 'unimplemented' }],
+      toDOM: data => ['span', { class: `unimplemented` }],
     },
   },
 });
@@ -151,6 +159,8 @@ export const factory = {
     schema.nodes.policy.create({}, children || []),
   sec: (children?: Node[] | Fragment) =>
     schema.nodes.sec.create({}, children || []),
+  external_link: (href: string) =>
+    schema.marks.external_link.create({ href }),
   unimplementedMark: (original: any) =>
     schema.marks.unimplementedMark.create({ data: original }),
   unimplementedNode: (original: any) =>
diff --git a/api/document/js/serialize-doc.ts b/api/document/js/serialize-doc.ts
index 54c7ffb91..e2d699438 100644
--- a/api/document/js/serialize-doc.ts
+++ b/api/document/js/serialize-doc.ts
@@ -94,8 +94,10 @@ function defaultNodeConverter(node: Node): ApiNode {
 }
 
 const MARK_CONVERTERS = {
-  unimplementedMark: node =>
-    apiFactory.content(node.type.name, node.attrs.data),
+  unimplementedMark: mark =>
+    apiFactory.content(mark.type.name, mark.attrs.data),
+  external_link: mark =>
+  apiFactory.content(mark.type.name, { href: mark.attrs.href }),
 };