diff --git a/src/jvmMain/kotlin/com/sunnychung/application/multiplatform/hellohttp/ux/bigtext/BigTextTransformer.kt b/src/jvmMain/kotlin/com/sunnychung/application/multiplatform/hellohttp/ux/bigtext/BigTextTransformer.kt
index faa7304d..844b03e4 100644
--- a/src/jvmMain/kotlin/com/sunnychung/application/multiplatform/hellohttp/ux/bigtext/BigTextTransformer.kt
+++ b/src/jvmMain/kotlin/com/sunnychung/application/multiplatform/hellohttp/ux/bigtext/BigTextTransformer.kt
@@ -16,5 +16,5 @@ interface BigTextTransformer {
 
     fun replace(range: IntRange, text: String, offsetMapping: BigTextTransformOffsetMapping)
 
-//    fun restoreToOriginal(range: IntRange)
+    fun restoreToOriginal(range: IntRange)
 }
diff --git a/src/jvmMain/kotlin/com/sunnychung/application/multiplatform/hellohttp/ux/bigtext/BigTextTransformerImpl.kt b/src/jvmMain/kotlin/com/sunnychung/application/multiplatform/hellohttp/ux/bigtext/BigTextTransformerImpl.kt
index 978d4194..72a8df08 100644
--- a/src/jvmMain/kotlin/com/sunnychung/application/multiplatform/hellohttp/ux/bigtext/BigTextTransformerImpl.kt
+++ b/src/jvmMain/kotlin/com/sunnychung/application/multiplatform/hellohttp/ux/bigtext/BigTextTransformerImpl.kt
@@ -92,19 +92,24 @@ class BigTextTransformerImpl(internal val delegate: BigTextImpl) : BigTextImpl(c
         return BigTextTransformNodeValue()
     }
 
-    fun insertOriginal(pos: Int, nodeValue: BigTextNodeValue) {
-        require(pos in 0 .. originalLength) { "Out of bound. pos = $pos, originalLength = $originalLength" }
+    fun insertOriginal(
+        pos: Int,
+        nodeValue: BigTextNodeValue,
+        bufferOffsetStart: Int = nodeValue.bufferOffsetStart,
+        bufferOffsetEndExclusive: Int = nodeValue.bufferOffsetEndExclusive,
+    ) {
+        require(pos in 0..originalLength) { "Out of bound. pos = $pos, originalLength = $originalLength" }
 
         insertChunkAtPosition(
             position = pos,
-            chunkedStringLength = nodeValue.bufferLength,
+            chunkedStringLength = bufferOffsetEndExclusive - bufferOffsetStart,
             ownership = BufferOwnership.Delegated,
             buffer = nodeValue.buffer,
-            range = nodeValue.bufferOffsetStart until nodeValue.bufferOffsetEndExclusive
+            range = bufferOffsetStart until bufferOffsetEndExclusive
         ) {
             bufferIndex = -1
-            bufferOffsetStart = nodeValue.bufferOffsetStart
-            bufferOffsetEndExclusive = nodeValue.bufferOffsetEndExclusive
+            this.bufferOffsetStart = bufferOffsetStart
+            this.bufferOffsetEndExclusive = bufferOffsetEndExclusive
             this.buffer = nodeValue.buffer
             this.bufferOwnership = BufferOwnership.Delegated
 
@@ -521,6 +526,41 @@ class BigTextTransformerImpl(internal val delegate: BigTextImpl) : BigTextImpl(c
     override fun replace(range: IntRange, text: String) = transformReplace(range, text)
 
     override fun replace(range: IntRange, text: String, offsetMapping: BigTextTransformOffsetMapping) = transformReplace(range, text, offsetMapping)
+
+    override fun restoreToOriginal(range: IntRange) {
+        val renderPositionAtOriginalStart = findTransformedPositionByOriginalPosition(range.start)
+        val renderPositionAtOriginalEnd = findTransformedPositionByOriginalPosition(range.endInclusive)
+
+        deleteTransformIf(range)
+        deleteOriginal(range)
+
+        // insert the original text from `delegate`
+        val originalNodeStart = delegate.tree.findNodeByCharIndex(range.start)
+            ?: throw IndexOutOfBoundsException("Original node at position ${range.start} not found")
+        var nodePositionStart = delegate.tree.findPositionStart(originalNodeStart)
+        var insertPoint = range.start
+        var node = originalNodeStart
+        var insertOffsetStart = node.value.bufferOffsetStart + (range.start - nodePositionStart)
+        do {
+            val insertOffsetEndExclusive = if ((nodePositionStart + node.value.bufferLength) > (range.endInclusive + 1)) {
+                node.value.bufferOffsetStart + (range.endInclusive + 1 - nodePositionStart)
+            } else {
+                node.value.bufferOffsetEndExclusive
+            }
+            insertOriginal(insertPoint, node.value, insertOffsetStart, insertOffsetEndExclusive)
+
+            if (insertPoint + (insertOffsetEndExclusive - insertOffsetStart) > range.endInclusive) {
+                break
+            }
+
+            node = delegate.tree.nextNode(node)!!
+            nodePositionStart = delegate.tree.findPositionStart(node)
+            insertPoint += insertOffsetEndExclusive - insertOffsetStart
+            insertOffsetStart = node.value.bufferOffsetStart
+        } while (nodePositionStart <= range.endInclusive)
+
+        layout(maxOf(0, renderPositionAtOriginalStart - 1), minOf(length, renderPositionAtOriginalEnd + 1))
+    }
 }
 
 fun RedBlackTree<BigTextTransformNodeValue>.Node.transformedOffset(): Int =
diff --git a/src/jvmTest/kotlin/com/sunnychung/application/multiplatform/hellohttp/test/bigtext/transform/BigTextTransformerImplTest.kt b/src/jvmTest/kotlin/com/sunnychung/application/multiplatform/hellohttp/test/bigtext/transform/BigTextTransformerImplTest.kt
index 26c3f999..5ecce278 100644
--- a/src/jvmTest/kotlin/com/sunnychung/application/multiplatform/hellohttp/test/bigtext/transform/BigTextTransformerImplTest.kt
+++ b/src/jvmTest/kotlin/com/sunnychung/application/multiplatform/hellohttp/test/bigtext/transform/BigTextTransformerImplTest.kt
@@ -3,6 +3,7 @@ package com.sunnychung.application.multiplatform.hellohttp.test.bigtext.transfor
 import com.sunnychung.application.multiplatform.hellohttp.test.bigtext.randomString
 import com.sunnychung.application.multiplatform.hellohttp.ux.bigtext.BigText
 import com.sunnychung.application.multiplatform.hellohttp.ux.bigtext.BigTextImpl
+import com.sunnychung.application.multiplatform.hellohttp.ux.bigtext.BigTextTransformOffsetMapping
 import com.sunnychung.application.multiplatform.hellohttp.ux.bigtext.BigTextTransformerImpl
 import com.sunnychung.application.multiplatform.hellohttp.ux.bigtext.isD
 import org.junit.jupiter.api.BeforeEach
@@ -895,6 +896,67 @@ class BigTextTransformerImplTest {
         }
     }
 
+    @ParameterizedTest
+    @ValueSource(ints = [1048576, 64, 16])
+    fun restoreToOriginal(chunkSize: Int) {
+        val initialText = "12345678901234567890123456789012345678901234567890123456789012345678901234567890"
+        val original = BigTextImpl(chunkSize = chunkSize)
+        original.append(initialText)
+        val transformed = BigTextTransformerImpl(original)
+
+        transformed.replace(11 .. 18, "ABCD", BigTextTransformOffsetMapping.Incremental)
+        "12345678901ABCD0123456789012345678901234567890123456789012345678901234567890".let { expected ->
+            assertEquals(expected, transformed.buildString())
+            assertEquals(initialText, original.buildString())
+            assertAllSubstring(expected, transformed)
+        }
+
+        transformed.insertAt(61, "EFGHIJ")
+        "12345678901ABCD012345678901234567890123456789012345678901EFGHIJ2345678901234567890".let { expected ->
+            assertEquals(expected, transformed.buildString())
+            assertEquals(initialText, original.buildString())
+            assertAllSubstring(expected, transformed)
+        }
+
+        transformed.restoreToOriginal(0 .. initialText.length - 1)
+        initialText.let { expected ->
+            assertEquals(expected, transformed.buildString())
+            assertEquals(expected, original.buildString())
+            assertAllSubstring(expected, transformed)
+        }
+    }
+
+    @ParameterizedTest
+    @ValueSource(ints = [1048576, 64, 16])
+    fun restoreToOriginalThenOriginalDelete(chunkSize: Int) {
+        val initialText = "12345678901234567890123456789012345678901234567890123456789012345678901234567890"
+        val original = BigTextImpl(chunkSize = chunkSize)
+        original.append(initialText)
+        val transformed = BigTextTransformerImpl(original)
+
+        transformed.replace(11 .. 18, "ABCD", BigTextTransformOffsetMapping.WholeBlock)
+        "12345678901ABCD0123456789012345678901234567890123456789012345678901234567890".let { expected ->
+            assertEquals(expected, transformed.buildString())
+            assertEquals(initialText, original.buildString())
+            assertAllSubstring(expected, transformed)
+        }
+
+        transformed.restoreToOriginal(11 .. 18)
+        initialText.let { expected ->
+            assertEquals(expected, transformed.buildString())
+            assertEquals(expected, original.buildString())
+            assertAllSubstring(expected, transformed)
+        }
+
+        original.delete(18 .. 18)
+
+        "1234567890123456780123456789012345678901234567890123456789012345678901234567890".let { expected ->
+            assertEquals(expected, original.buildString())
+            assertEquals(expected, transformed.buildString())
+            assertAllSubstring(expected, transformed)
+        }
+    }
+
     @BeforeEach
     fun beforeEach() {
         isD = false