diff --git a/src/editor/model.js b/src/editor/model.js
index 2f1e5218d8..c5b80247f6 100644
--- a/src/editor/model.js
+++ b/src/editor/model.js
@@ -16,6 +16,8 @@ limitations under the License.
 */
 
 import {diffAtCaret, diffDeletion} from "./diff";
+import DocumentPosition from "./position";
+import Range from "./range";
 
 export default class EditorModel {
     constructor(parts, partCreator, updateCallback = null) {
@@ -197,7 +199,7 @@ export default class EditorModel {
         this._updateCallback(pos);
     }
 
-    _mergeAdjacentParts(docPos) {
+    _mergeAdjacentParts() {
         let prevPart;
         for (let i = 0; i < this._parts.length; ++i) {
             let part = this._parts[i];
@@ -339,19 +341,32 @@ export default class EditorModel {
 
         return new DocumentPosition(index, totalOffset - currentOffset);
     }
-}
 
-class DocumentPosition {
-    constructor(index, offset) {
-        this._index = index;
-        this._offset = offset;
+    startRange(position) {
+        return new Range(this, position);
     }
 
-    get index() {
-        return this._index;
-    }
-
-    get offset() {
-        return this._offset;
+    // called from Range.replace
+    replaceRange(startPosition, endPosition, parts) {
+        const newStartPartIndex = this._splitAt(startPosition);
+        const idxDiff = newStartPartIndex - startPosition.index;
+        // if both position are in the same part, and we split it at start position,
+        // the offset of the end position needs to be decreased by the offset of the start position
+        const removedOffset = startPosition.index === endPosition.index ? startPosition.offset : 0;
+        const adjustedEndPosition = new DocumentPosition(
+            endPosition.index + idxDiff,
+            endPosition.offset - removedOffset,
+        );
+        const newEndPartIndex = this._splitAt(adjustedEndPosition);
+        for (let i = newEndPartIndex - 1; i >= newStartPartIndex; --i) {
+            this._removePart(i);
+        }
+        let insertIdx = newStartPartIndex;
+        for (const part of parts) {
+            this._insertPart(insertIdx, part);
+            insertIdx += 1;
+        }
+        this._mergeAdjacentParts();
+        this._updateCallback();
     }
 }
diff --git a/src/editor/position.js b/src/editor/position.js
new file mode 100644
index 0000000000..c771482012
--- /dev/null
+++ b/src/editor/position.js
@@ -0,0 +1,38 @@
+/*
+Copyright 2019 The Matrix.org Foundation C.I.C.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+export default class DocumentPosition {
+    constructor(index, offset) {
+        this._index = index;
+        this._offset = offset;
+    }
+
+    get index() {
+        return this._index;
+    }
+
+    get offset() {
+        return this._offset;
+    }
+
+    compare(otherPos) {
+        if (this._index === otherPos._index) {
+            return this._offset - otherPos._offset;
+        } else {
+            return this._index - otherPos._index;
+        }
+    }
+}
diff --git a/src/editor/range.js b/src/editor/range.js
new file mode 100644
index 0000000000..e2ecc5d12b
--- /dev/null
+++ b/src/editor/range.js
@@ -0,0 +1,53 @@
+/*
+Copyright 2019 The Matrix.org Foundation C.I.C.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+export default class Range {
+    constructor(model, startPosition, endPosition = startPosition) {
+        this._model = model;
+        this._start = startPosition;
+        this._end = endPosition;
+    }
+
+    moveStart(delta) {
+        this._start = this._start.forwardsWhile(this._model, () => {
+            delta -= 1;
+            return delta >= 0;
+        });
+    }
+
+    expandBackwardsWhile(predicate) {
+        this._start = this._start.backwardsWhile(this._model, predicate);
+    }
+
+    get text() {
+        let text = "";
+        this._start.iteratePartsBetween(this._end, this._model, (part, startIdx, endIdx) => {
+            const t = part.text.substring(startIdx, endIdx);
+            text = text + t;
+        });
+        return text;
+    }
+
+    replace(parts) {
+        const newLength = parts.reduce((sum, part) => sum + part.text.length, 0);
+        let oldLength = 0;
+        this._start.iteratePartsBetween(this._end, this._model, (part, startIdx, endIdx) => {
+            oldLength += endIdx - startIdx;
+        });
+        this._model.replaceRange(this._start, this._end, parts);
+        return newLength - oldLength;
+    }
+}
diff --git a/test/editor/range-test.js b/test/editor/range-test.js
new file mode 100644
index 0000000000..5a95da952d
--- /dev/null
+++ b/test/editor/range-test.js
@@ -0,0 +1,88 @@
+/*
+Copyright 2019 The Matrix.org Foundation C.I.C.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+import expect from 'expect';
+import EditorModel from "../../src/editor/model";
+import {createPartCreator} from "./mock";
+
+function createRenderer() {
+    const render = (c) => {
+        render.caret = c;
+        render.count += 1;
+    };
+    render.count = 0;
+    render.caret = null;
+    return render;
+}
+
+const pillChannel = "#riot-dev:matrix.org";
+
+describe('editor/range', function() {
+    it('range on empty model', function() {
+        const renderer = createRenderer();
+        const pc = createPartCreator();
+        const model = new EditorModel([], pc, renderer);
+        const range = model.startRange(model.positionForOffset(0, true));  // after "world"
+        let called = false;
+        range.expandBackwardsWhile(chr => {
+            called = true;
+            return true;
+        });
+        expect(called).toBe(false);
+        expect(range.text).toBe("");
+    });
+    it('range replace within a part', function() {
+        const renderer = createRenderer();
+        const pc = createPartCreator();
+        const model = new EditorModel([pc.plain("hello world!!!!")], pc, renderer);
+        const range = model.startRange(model.positionForOffset(11));  // after "world"
+        range.expandBackwardsWhile((index, offset) => model.parts[index].text[offset] !== " ");
+        expect(range.text).toBe("world");
+        range.replace([pc.roomPill(pillChannel)]);
+        console.log({parts: JSON.stringify(model.serializeParts())});
+        expect(model.parts[0].type).toBe("plain");
+        expect(model.parts[0].text).toBe("hello ");
+        expect(model.parts[1].type).toBe("room-pill");
+        expect(model.parts[1].text).toBe(pillChannel);
+        expect(model.parts[2].type).toBe("plain");
+        expect(model.parts[2].text).toBe("!!!!");
+        expect(model.parts.length).toBe(3);
+        expect(renderer.count).toBe(1);
+    });
+    it('range replace across parts', function() {
+        const renderer = createRenderer();
+        const pc = createPartCreator();
+        const model = new EditorModel([
+            pc.plain("try to re"),
+            pc.plain("pla"),
+            pc.plain("ce "),
+            pc.plain("me"),
+        ], pc, renderer);
+        const range = model.startRange(model.positionForOffset(14));  // after "replace"
+        range.expandBackwardsWhile((index, offset) => model.parts[index].text[offset] !== " ");
+        expect(range.text).toBe("replace");
+        console.log("range.text", {text: range.text});
+        range.replace([pc.roomPill(pillChannel)]);
+        expect(model.parts[0].type).toBe("plain");
+        expect(model.parts[0].text).toBe("try to ");
+        expect(model.parts[1].type).toBe("room-pill");
+        expect(model.parts[1].text).toBe(pillChannel);
+        expect(model.parts[2].type).toBe("plain");
+        expect(model.parts[2].text).toBe(" me");
+        expect(model.parts.length).toBe(3);
+        expect(renderer.count).toBe(1);
+    });
+});