diff --git a/locales/ar-SA/opencadstudio.ftl b/locales/ar-SA/opencadstudio.ftl
index d7f98e422..eea138efa 100644
--- a/locales/ar-SA/opencadstudio.ftl
+++ b/locales/ar-SA/opencadstudio.ftl
@@ -295,6 +295,9 @@ command-copy =
     .mode = COPY  أدخل خيار وضع النسخ [Single/Multiple] <Multiple>:
 
 common =
+    .compare-prompt = COMPARE  __ocs_fmt_0__ هنا فقط (أخضر)، __ocs_fmt_1__ في الرسم الآخر فقط (أحمر)__ocs_fmt_2__ [Next/Previous/eXit]:
+    .compare-error = COMPARE: __ocs_fmt_0__
+    .compare-with-drawing = مقارنة مع رسم
     .label-associative-array-created = __ocs_fmt_0__: تم إنشاء مصفوفة ترابطية.
     .assoc-array-array-path = مصفوفة (مسار)
     .assoc-array-array-polar = مصفوفة (قطبية)
diff --git a/locales/bg-BG/opencadstudio.ftl b/locales/bg-BG/opencadstudio.ftl
index cb7085f4d..feee17bdc 100644
--- a/locales/bg-BG/opencadstudio.ftl
+++ b/locales/bg-BG/opencadstudio.ftl
@@ -282,6 +282,9 @@ command-copy =
     .displacement = COPY  Задайте преместване:
     .mode = COPY  Въведете режим на копиране [Single/Multiple] <Multiple>:
 common =
+    .compare-prompt = COMPARE  __ocs_fmt_0__ само тук (зелено), __ocs_fmt_1__ само в другия чертеж (червено)__ocs_fmt_2__ [Next/Previous/eXit]:
+    .compare-error = COMPARE: __ocs_fmt_0__
+    .compare-with-drawing = Сравняване с чертеж
     .label-associative-array-created = __ocs_fmt_0__: създаден е асоциативен масив.
     .assoc-array-array-path = Масив (по път)
     .assoc-array-array-polar = Масив (полярен)
diff --git a/locales/cs-CZ/opencadstudio.ftl b/locales/cs-CZ/opencadstudio.ftl
index 71bf17c6f..a32db3547 100644
--- a/locales/cs-CZ/opencadstudio.ftl
+++ b/locales/cs-CZ/opencadstudio.ftl
@@ -282,6 +282,9 @@ command-copy =
     .mode = COPY  Zadejte režim kopírování [Single/Multiple] <Multiple>:
 
 common =
+    .compare-prompt = COMPARE  __ocs_fmt_0__ jen zde (zeleně), __ocs_fmt_1__ jen v druhém výkresu (červeně)__ocs_fmt_2__ [Next/Previous/eXit]:
+    .compare-error = COMPARE: __ocs_fmt_0__
+    .compare-with-drawing = Porovnat s výkresem
     .label-associative-array-created = __ocs_fmt_0__: vytvořeno asociativní pole.
     .assoc-array-array-path = Pole (podél cesty)
     .assoc-array-array-polar = Pole (kruhové)
diff --git a/locales/de-DE/opencadstudio.ftl b/locales/de-DE/opencadstudio.ftl
index 6ef673520..42ce8800d 100644
--- a/locales/de-DE/opencadstudio.ftl
+++ b/locales/de-DE/opencadstudio.ftl
@@ -283,6 +283,9 @@ command-copy =
     .mode = COPY  Kopiermodus eingeben [Single/Multiple] <Multiple>:
 
 common =
+    .compare-prompt = COMPARE  __ocs_fmt_0__ nur hier (grün), __ocs_fmt_1__ nur in der anderen Zeichnung (rot)__ocs_fmt_2__ [Next/Previous/eXit]:
+    .compare-error = COMPARE: __ocs_fmt_0__
+    .compare-with-drawing = Mit Zeichnung vergleichen
     .label-associative-array-created = __ocs_fmt_0__: assoziative Reihe erstellt.
     .assoc-array-array-path = Reihe (Pfad)
     .assoc-array-array-polar = Reihe (polar)
diff --git a/locales/el-GR/opencadstudio.ftl b/locales/el-GR/opencadstudio.ftl
index 48f3a6273..f5646e118 100644
--- a/locales/el-GR/opencadstudio.ftl
+++ b/locales/el-GR/opencadstudio.ftl
@@ -282,6 +282,9 @@ command-copy =
     .mode = COPY  Επιλέξτε λειτουργία αντιγραφής [Single/Multiple] <Multiple>:
 
 common =
+    .compare-prompt = COMPARE  __ocs_fmt_0__ μόνο εδώ (πράσινο), __ocs_fmt_1__ μόνο στο άλλο σχέδιο (κόκκινο)__ocs_fmt_2__ [Next/Previous/eXit]:
+    .compare-error = COMPARE: __ocs_fmt_0__
+    .compare-with-drawing = Σύγκριση με σχέδιο
     .label-associative-array-created = __ocs_fmt_0__: δημιουργήθηκε συσχετιστικός πίνακας.
     .assoc-array-array-path = Πίνακας (διαδρομή)
     .assoc-array-array-polar = Πίνακας (πολικός)
diff --git a/locales/en-US/opencadstudio.ftl b/locales/en-US/opencadstudio.ftl
index d1781a219..f2539ea74 100644
--- a/locales/en-US/opencadstudio.ftl
+++ b/locales/en-US/opencadstudio.ftl
@@ -282,6 +282,9 @@ command-copy =
     .mode = COPY  Enter a copy mode option [Single/Multiple] <Multiple>:
 
 common =
+    .compare-prompt = COMPARE  __ocs_fmt_0__ only here (green), __ocs_fmt_1__ only in the other drawing (red)__ocs_fmt_2__ [Next/Previous/eXit]:
+    .compare-error = COMPARE: __ocs_fmt_0__
+    .compare-with-drawing = Compare with drawing
     .label-associative-array-created = __ocs_fmt_0__: associative array created.
     .assoc-array-array-path = Array (Path)
     .assoc-array-array-polar = Array (Polar)
diff --git a/locales/es-ES/opencadstudio.ftl b/locales/es-ES/opencadstudio.ftl
index 96d19d420..47ec91dcf 100644
--- a/locales/es-ES/opencadstudio.ftl
+++ b/locales/es-ES/opencadstudio.ftl
@@ -283,6 +283,9 @@ command-copy =
     .mode = COPY  Indique modo de copia [Single/Multiple] <Multiple>:
 
 common =
+    .compare-prompt = COMPARE  __ocs_fmt_0__ solo aquí (verde), __ocs_fmt_1__ solo en el otro dibujo (rojo)__ocs_fmt_2__ [Next/Previous/eXit]:
+    .compare-error = COMPARE: __ocs_fmt_0__
+    .compare-with-drawing = Comparar con dibujo
     .label-associative-array-created = __ocs_fmt_0__: se ha creado una matriz asociativa.
     .assoc-array-array-path = Matriz (trayectoria)
     .assoc-array-array-polar = Matriz (polar)
diff --git a/locales/fi-FI/opencadstudio.ftl b/locales/fi-FI/opencadstudio.ftl
index 672a1be0e..1eb2acba2 100644
--- a/locales/fi-FI/opencadstudio.ftl
+++ b/locales/fi-FI/opencadstudio.ftl
@@ -282,6 +282,9 @@ command-copy =
     .mode = COPY  Valitse kopiointitila [Single/Multiple] <Multiple>:
 
 common =
+    .compare-prompt = COMPARE  __ocs_fmt_0__ vain täällä (vihreä), __ocs_fmt_1__ vain toisessa piirustuksessa (punainen)__ocs_fmt_2__ [Next/Previous/eXit]:
+    .compare-error = COMPARE: __ocs_fmt_0__
+    .compare-with-drawing = Vertaa piirustukseen
     .label-associative-array-created = __ocs_fmt_0__: assosiatiivinen taulukko luotu.
     .assoc-array-array-path = Taulukko (polku)
     .assoc-array-array-polar = Taulukko (polaarinen)
diff --git a/locales/fr-FR/opencadstudio.ftl b/locales/fr-FR/opencadstudio.ftl
index eb9f59748..1193628d7 100644
--- a/locales/fr-FR/opencadstudio.ftl
+++ b/locales/fr-FR/opencadstudio.ftl
@@ -283,6 +283,9 @@ command-copy =
     .mode = COPY  Entrez le mode de copie [Single/Multiple] <Multiple> :
 
 common =
+    .compare-prompt = COMPARE  __ocs_fmt_0__ seulement ici (vert), __ocs_fmt_1__ seulement dans l’autre dessin (rouge)__ocs_fmt_2__ [Next/Previous/eXit] :
+    .compare-error = COMPARE: __ocs_fmt_0__
+    .compare-with-drawing = Comparer avec un dessin
     .label-associative-array-created = __ocs_fmt_0__ : réseau associatif créé.
     .assoc-array-array-path = Réseau (trajectoire)
     .assoc-array-array-polar = Réseau (polaire)
diff --git a/locales/hi-IN/opencadstudio.ftl b/locales/hi-IN/opencadstudio.ftl
index 6c58c7b57..d3a7193ef 100644
--- a/locales/hi-IN/opencadstudio.ftl
+++ b/locales/hi-IN/opencadstudio.ftl
@@ -271,6 +271,9 @@ command-copy =
     .mode = COPY  कॉपी मोड विकल्प दर्ज करें [Single/Multiple] <Multiple>:
 
 common =
+    .compare-prompt = COMPARE  __ocs_fmt_0__ केवल यहाँ (हरा), __ocs_fmt_1__ केवल दूसरी ड्रॉइंग में (लाल)__ocs_fmt_2__ [Next/Previous/eXit]:
+    .compare-error = COMPARE: __ocs_fmt_0__
+    .compare-with-drawing = ड्रॉइंग से तुलना करें
     .label-associative-array-created = __ocs_fmt_0__: सहयोगी ऐरे बनाया गया।
     .assoc-array-array-path = ऐरे (पथ)
     .assoc-array-array-polar = ऐरे (ध्रुवीय)
diff --git a/locales/hu-HU/opencadstudio.ftl b/locales/hu-HU/opencadstudio.ftl
index 75d445a98..a5e19f84a 100644
--- a/locales/hu-HU/opencadstudio.ftl
+++ b/locales/hu-HU/opencadstudio.ftl
@@ -281,6 +281,9 @@ command-copy =
     .mode = COPY  Adja meg a másolási módot [Single/Multiple] <Multiple>:
 
 common =
+    .compare-prompt = COMPARE  __ocs_fmt_0__ csak itt (zöld), __ocs_fmt_1__ csak a másik rajzban (piros)__ocs_fmt_2__ [Next/Previous/eXit]:
+    .compare-error = COMPARE: __ocs_fmt_0__
+    .compare-with-drawing = Összehasonlítás rajzzal
     .label-associative-array-created = __ocs_fmt_0__: asszociatív tömb létrehozva.
     .assoc-array-array-path = Tömb (útvonal)
     .assoc-array-array-polar = Tömb (poláris)
diff --git a/locales/it-IT/opencadstudio.ftl b/locales/it-IT/opencadstudio.ftl
index fc91c30db..ee88209fc 100644
--- a/locales/it-IT/opencadstudio.ftl
+++ b/locales/it-IT/opencadstudio.ftl
@@ -282,6 +282,9 @@ command-copy =
     .mode = COPY  Specificare modalità di copia [Single/Multiple] <Multiple>:
 
 common =
+    .compare-prompt = COMPARE  __ocs_fmt_0__ solo qui (verde), __ocs_fmt_1__ solo nell'altro disegno (rosso)__ocs_fmt_2__ [Next/Previous/eXit]:
+    .compare-error = COMPARE: __ocs_fmt_0__
+    .compare-with-drawing = Confronta con disegno
     .label-associative-array-created = __ocs_fmt_0__: serie associativa creata.
     .assoc-array-array-path = Serie (percorso)
     .assoc-array-array-polar = Serie (polare)
diff --git a/locales/ja-JP/opencadstudio.ftl b/locales/ja-JP/opencadstudio.ftl
index 5fbb8a6e6..c404bf79d 100644
--- a/locales/ja-JP/opencadstudio.ftl
+++ b/locales/ja-JP/opencadstudio.ftl
@@ -273,6 +273,9 @@ command-copy =
     .mode = COPY  コピーモードを入力 [Single/Multiple] <Multiple>:
 
 common =
+    .compare-prompt = COMPARE  ここのみ __ocs_fmt_0__ (緑)、もう一方の図面のみ __ocs_fmt_1__ (赤)__ocs_fmt_2__ [Next/Previous/eXit]:
+    .compare-error = COMPARE: __ocs_fmt_0__
+    .compare-with-drawing = 図面と比較
     .label-associative-array-created = __ocs_fmt_0__: 自動調整配列複写を作成しました。
     .assoc-array-array-path = 配列複写 (パス)
     .assoc-array-array-polar = 配列複写 (円形状)
diff --git a/locales/ko-KR/opencadstudio.ftl b/locales/ko-KR/opencadstudio.ftl
index 8d25f85c4..9b090c1b2 100644
--- a/locales/ko-KR/opencadstudio.ftl
+++ b/locales/ko-KR/opencadstudio.ftl
@@ -282,6 +282,9 @@ command-copy =
     .mode = COPY  복사 모드 옵션 입력 [Single/Multiple] <Multiple>:
 
 common =
+    .compare-prompt = COMPARE  여기에만 __ocs_fmt_0__ (녹색), 다른 도면에만 __ocs_fmt_1__ (빨간색)__ocs_fmt_2__ [Next/Previous/eXit]:
+    .compare-error = COMPARE: __ocs_fmt_0__
+    .compare-with-drawing = 도면과 비교
     .label-associative-array-created = __ocs_fmt_0__: 연관 배열을 만들었습니다.
     .assoc-array-array-path = 배열 (경로)
     .assoc-array-array-polar = 배열 (원형)
diff --git a/locales/lo-LA/opencadstudio.ftl b/locales/lo-LA/opencadstudio.ftl
index c188faa06..daa8e1ac4 100644
--- a/locales/lo-LA/opencadstudio.ftl
+++ b/locales/lo-LA/opencadstudio.ftl
@@ -282,6 +282,9 @@ command-copy =
     .mode = COPY  ປ້ອນຕົວເລືອກໂໝດການຄັດລອກ [Single/Multiple] <Multiple>:
 
 common =
+    .compare-prompt = COMPARE  __ocs_fmt_0__ ຢູ່ນີ້ເທົ່ານັ້ນ (ຂຽວ), __ocs_fmt_1__ ຢູ່ໃນແບບອື່ນເທົ່ານັ້ນ (ແດງ)__ocs_fmt_2__ [Next/Previous/eXit]:
+    .compare-error = COMPARE: __ocs_fmt_0__
+    .compare-with-drawing = ປຽບທຽບກັບແບບ
     .label-associative-array-created = __ocs_fmt_0__: ສ້າງອາເຣແບບເຊື່ອມໂຍງແລ້ວ.
     .assoc-array-array-path = ອາເຣ (ເສັ້ນທາງ)
     .assoc-array-array-polar = ອາເຣ (ວົງມົນ)
diff --git a/locales/nl-NL/opencadstudio.ftl b/locales/nl-NL/opencadstudio.ftl
index f621a55f9..aa2947764 100644
--- a/locales/nl-NL/opencadstudio.ftl
+++ b/locales/nl-NL/opencadstudio.ftl
@@ -283,6 +283,9 @@ command-copy =
     .mode = COPY  Geef kopieermodus op [Single/Multiple] <Multiple>:
 
 common =
+    .compare-prompt = COMPARE  __ocs_fmt_0__ alleen hier (groen), __ocs_fmt_1__ alleen in de andere tekening (rood)__ocs_fmt_2__ [Next/Previous/eXit]:
+    .compare-error = COMPARE: __ocs_fmt_0__
+    .compare-with-drawing = Vergelijken met tekening
     .label-associative-array-created = __ocs_fmt_0__: associatieve reeks gemaakt.
     .assoc-array-array-path = Reeks (pad)
     .assoc-array-array-polar = Reeks (polair)
diff --git a/locales/pl-PL/opencadstudio.ftl b/locales/pl-PL/opencadstudio.ftl
index 648827533..e14539fb9 100644
--- a/locales/pl-PL/opencadstudio.ftl
+++ b/locales/pl-PL/opencadstudio.ftl
@@ -282,6 +282,9 @@ command-copy =
     .mode = COPY  Podaj tryb kopiowania [Single/Multiple] <Multiple>:
 
 common =
+    .compare-prompt = COMPARE  __ocs_fmt_0__ tylko tutaj (zielone), __ocs_fmt_1__ tylko w drugim rysunku (czerwone)__ocs_fmt_2__ [Next/Previous/eXit]:
+    .compare-error = COMPARE: __ocs_fmt_0__
+    .compare-with-drawing = Porównaj z rysunkiem
     .label-associative-array-created = __ocs_fmt_0__: utworzono szyk skojarzony.
     .assoc-array-array-path = Szyk (ścieżka)
     .assoc-array-array-polar = Szyk (biegunowy)
diff --git a/locales/pt-BR/opencadstudio.ftl b/locales/pt-BR/opencadstudio.ftl
index eacb449da..a27c55e6f 100644
--- a/locales/pt-BR/opencadstudio.ftl
+++ b/locales/pt-BR/opencadstudio.ftl
@@ -283,6 +283,9 @@ command-copy =
     .mode = COPY  Informe o modo de cópia [Single/Multiple] <Multiple>:
 
 common =
+    .compare-prompt = COMPARE  __ocs_fmt_0__ só aqui (verde), __ocs_fmt_1__ só no outro desenho (vermelho)__ocs_fmt_2__ [Next/Previous/eXit]:
+    .compare-error = COMPARE: __ocs_fmt_0__
+    .compare-with-drawing = Comparar com desenho
     .label-associative-array-created = __ocs_fmt_0__: matriz associativa criada.
     .assoc-array-array-path = Matriz (caminho)
     .assoc-array-array-polar = Matriz (polar)
diff --git a/locales/ru-RU/opencadstudio.ftl b/locales/ru-RU/opencadstudio.ftl
index eac8d2f50..8ce95ea49 100644
--- a/locales/ru-RU/opencadstudio.ftl
+++ b/locales/ru-RU/opencadstudio.ftl
@@ -286,6 +286,9 @@ command-copy =
     .mode = COPY  Задайте режим копирования [Single/Multiple] <Multiple>:
 
 common =
+    .compare-prompt = COMPARE  __ocs_fmt_0__ только здесь (зелёные), __ocs_fmt_1__ только в другом чертеже (красные)__ocs_fmt_2__ [Next/Previous/eXit]:
+    .compare-error = COMPARE: __ocs_fmt_0__
+    .compare-with-drawing = Сравнить с чертежом
     .label-associative-array-created = __ocs_fmt_0__: создан ассоциативный массив.
     .assoc-array-array-path = Массив (по траектории)
     .assoc-array-array-polar = Массив (круговой)
diff --git a/locales/tr-TR/opencadstudio.ftl b/locales/tr-TR/opencadstudio.ftl
index de6964037..5230c586a 100644
--- a/locales/tr-TR/opencadstudio.ftl
+++ b/locales/tr-TR/opencadstudio.ftl
@@ -268,6 +268,9 @@ command-copy =
     .mode = COPY  Kopyalama modu seçin [Single/Multiple] <Multiple>:
 
 common =
+    .compare-prompt = COMPARE  __ocs_fmt_0__ yalnızca burada (yeşil), __ocs_fmt_1__ yalnızca diğer çizimde (kırmızı)__ocs_fmt_2__ [Next/Previous/eXit]:
+    .compare-error = COMPARE: __ocs_fmt_0__
+    .compare-with-drawing = Çizimle karşılaştır
     .label-associative-array-created = __ocs_fmt_0__: ilişkisel dizi oluşturuldu.
     .assoc-array-array-path = Dizi (Yol)
     .assoc-array-array-polar = Dizi (Kutupsal)
diff --git a/locales/zh-CN/opencadstudio.ftl b/locales/zh-CN/opencadstudio.ftl
index c1c21d60e..87f586862 100644
--- a/locales/zh-CN/opencadstudio.ftl
+++ b/locales/zh-CN/opencadstudio.ftl
@@ -270,6 +270,9 @@ command-copy =
     .mode = COPY  输入复制模式选项 [Single/Multiple] <Multiple>:
 
 common =
+    .compare-prompt = COMPARE  仅此处 __ocs_fmt_0__ (绿色)，仅另一图形 __ocs_fmt_1__ (红色)__ocs_fmt_2__ [Next/Previous/eXit]:
+    .compare-error = COMPARE: __ocs_fmt_0__
+    .compare-with-drawing = 与图形比较
     .label-associative-array-created = __ocs_fmt_0__: 已创建关联阵列。
     .assoc-array-array-path = 阵列 (路径)
     .assoc-array-array-polar = 阵列 (环形)
diff --git a/locales/zh-TW/opencadstudio.ftl b/locales/zh-TW/opencadstudio.ftl
index 11dd5b6ee..57e1801ad 100644
--- a/locales/zh-TW/opencadstudio.ftl
+++ b/locales/zh-TW/opencadstudio.ftl
@@ -282,6 +282,9 @@ command-copy =
     .mode = COPY  輸入複製模式選項 [Single/Multiple] <Multiple>:
 
 common =
+    .compare-prompt = COMPARE  僅此處 __ocs_fmt_0__ (綠色)，僅另一圖面 __ocs_fmt_1__ (紅色)__ocs_fmt_2__ [Next/Previous/eXit]:
+    .compare-error = COMPARE: __ocs_fmt_0__
+    .compare-with-drawing = 與圖面比較
     .label-associative-array-created = __ocs_fmt_0__: 已建立關聯陣列。
     .assoc-array-array-path = 陣列 (路徑)
     .assoc-array-array-polar = 陣列 (環形)
diff --git a/src/app/command_driver/mod.rs b/src/app/command_driver/mod.rs
index 7c4a40807..9300ab80e 100644
--- a/src/app/command_driver/mod.rs
+++ b/src/app/command_driver/mod.rs
@@ -885,6 +885,11 @@ impl OpenCADStudio {
             CmdResult::ZoomToWindow { p1, p2 } => {
                 self.handle_zoom_to_window(p1, p2);
             }
+            CmdResult::Show { p1, p2 } => {
+                let i = self.active_tab;
+                self.tabs[i].scene.remember_current_view();
+                self.tabs[i].scene.zoom_to_window(p1.as_vec3(), p2.as_vec3());
+            }
             CmdResult::CommitAndZoom { entity, p1, p2 } => {
                 self.handle_commit_entities_and_exit(vec![entity], false, false);
                 self.handle_zoom_to_window(p1, p2);
diff --git a/src/app/commands/styleprops.rs b/src/app/commands/styleprops.rs
index fcf75ec7d..430256eaf 100644
--- a/src/app/commands/styleprops.rs
+++ b/src/app/commands/styleprops.rs
@@ -3335,6 +3335,42 @@ impl OpenCADStudio {
             // Read-only scan: flags entities on undefined layers and block
             // references to undefined block definitions. Reports only; it does
             // not auto-repair (so it can never make the drawing worse).
+            // COMPARE — overlay what differs from another drawing. Bare picks
+            // the drawing; with a path it compares at once.
+            "COMPARE" => {
+                return Some(Task::perform(
+                    async {
+                        crate::sys::file_dialog()
+                            .set_title(crate::t!("Compare with drawing").as_ref())
+                            .add_filter(crate::t!("Drawing").as_ref(), &["dwg", "dxf"])
+                            .pick_file()
+                            .await
+                            .map(|handle| crate::sys::handle_path(&handle))
+                    },
+                    |path| match path {
+                        Some(path) => Message::Command(format!("COMPARE {}", path.display())),
+                        None => Message::Noop,
+                    },
+                ));
+            }
+            cmd if cmd.starts_with("COMPARE ") => {
+                let path = std::path::PathBuf::from(cmd.trim_start_matches("COMPARE").trim());
+                match crate::io::load_file(&path) {
+                    Ok(other) => {
+                        let comparison =
+                            crate::scene::compare::compare(&self.tabs[i].scene, other);
+                        // The overlay shows at once, before the cursor moves.
+                        self.tabs[i].scene.set_preview_wires(comparison.overlay.clone());
+                        let command =
+                            crate::modules::manage::compare::CompareCommand::new(comparison);
+                        self.command_line.push_info(&command.prompt());
+                        self.tabs[i].active_cmd = Some(Box::new(command));
+                    }
+                    Err(error) => self
+                        .command_line
+                        .push_error(crate::tf!("COMPARE: {error}").as_ref()),
+                }
+            }
             "AUDIT" => {
                 use std::collections::BTreeSet;
                 let mut undefined_layers: BTreeSet<String> = BTreeSet::new();
diff --git a/src/command.rs b/src/command.rs
index b3b3a9b1c..6cd30c03c 100644
--- a/src/command.rs
+++ b/src/command.rs
@@ -1948,6 +1948,11 @@ pub enum CmdResult {
         p1: DVec3,
         p2: DVec3,
     },
+    /// Zoom to the given corner points; the command stays active.
+    Show {
+        p1: DVec3,
+        p2: DVec3,
+    },
     /// Commit `entity`, then zoom to the given corner points; end command.
     CommitAndZoom {
         entity: EntityType,
diff --git a/src/locale_catalog.rs b/src/locale_catalog.rs
index 9bb77b77b..4a4745e31 100644
--- a/src/locale_catalog.rs
+++ b/src/locale_catalog.rs
@@ -4227,6 +4227,9 @@ pub(super) fn message_attribute(source: &str) -> Option<(&'static str, &'static
         "UCS requires origin, X-axis point and XY-plane point." => Some(("common", "ucs-requires-origin-x-axis-point-and-xy-plane-point")),
         "DWGUNITS  current unit: {current}" => Some(("common", "dwgunits-current-unit")),
         "LAYTRANS: {why}." => Some(("common", "laytrans")),
+        "Compare with drawing" => Some(("common", "compare-with-drawing")),
+        "COMPARE: {error}" => Some(("common", "compare-error")),
+        "COMPARE  {added} only here (green), {removed} only in the other drawing (red){position} [Next/Previous/eXit]:" => Some(("common", "compare-prompt")),
         "LAYTRANS: no layer names in common — use LAYTRANS with no file to map them." => Some(("common", "laytrans-no-layer-names-in-common-use-laytrans-with-no-file-to-map-them")),
         "DWGUNITS: not a unit this drawing can use." => Some(("common", "dwgunits-not-a-unit-this-drawing-can-use")),
         "DWGUNITS: already in {label}." => Some(("common", "dwgunits-already-in")),
diff --git a/src/modules/manage/compare.rs b/src/modules/manage/compare.rs
new file mode 100644
index 000000000..45c4c05bd
--- /dev/null
+++ b/src/modules/manage/compare.rs
@@ -0,0 +1,104 @@
+// COMPARE — show what differs from another drawing and step through it.
+//
+//   COMPARE  <added> only here (green), <removed> only in the other drawing
+//   (red) [Next/Previous/eXit]:
+
+use crate::command::{CadCommand, CmdOption, CmdResult};
+use crate::scene::compare::Comparison;
+use crate::scene::WireModel;
+use glam::DVec3;
+
+pub struct CompareCommand {
+    comparison: Comparison,
+    /// The difference shown last; `None` before the first step.
+    current: Option<usize>,
+}
+
+impl CompareCommand {
+    pub fn new(comparison: Comparison) -> Self {
+        Self {
+            comparison,
+            current: None,
+        }
+    }
+
+    fn show(&mut self, forward: bool) -> CmdResult {
+        let count = self.comparison.spots.len();
+        if count == 0 {
+            return CmdResult::NeedPoint;
+        }
+        let next = match (self.current, forward) {
+            (None, true) => 0,
+            (None, false) => count - 1,
+            (Some(index), true) => (index + 1) % count,
+            (Some(index), false) => (index + count - 1) % count,
+        };
+        self.current = Some(next);
+        let (min, max) = self.comparison.spots[next];
+        // A margin around the difference so it is seen in its context.
+        let margin = ((max - min).length() * 0.5).max(1.0);
+        CmdResult::Show {
+            p1: min - DVec3::splat(margin),
+            p2: max + DVec3::splat(margin),
+        }
+    }
+}
+
+impl CadCommand for CompareCommand {
+    fn name(&self) -> &'static str {
+        "COMPARE"
+    }
+
+    fn prompt(&self) -> String {
+        let (added, removed) = (self.comparison.added, self.comparison.removed);
+        let position = match self.current {
+            Some(index) => format!(" {}/{}", index + 1, self.comparison.spots.len()),
+            None => String::new(),
+        };
+        crate::tf!(
+            "COMPARE  {added} only here (green), {removed} only in the other drawing (red){position} [Next/Previous/eXit]:"
+        )
+        .into_owned()
+    }
+
+    fn options(&self) -> Vec<CmdOption> {
+        vec![
+            CmdOption::new("Next", "N"),
+            CmdOption::new("Previous", "P"),
+            CmdOption::new("eXit", "X"),
+        ]
+    }
+
+    fn wants_text_input(&self) -> bool {
+        true
+    }
+
+    fn on_text_input(&mut self, text: &str) -> Option<CmdResult> {
+        match text.trim().trim_start_matches('_').to_ascii_uppercase().as_str() {
+            "" | "N" | "NEXT" => Some(self.show(true)),
+            "P" | "PREVIOUS" => Some(self.show(false)),
+            "X" | "EXIT" => Some(CmdResult::Cancel),
+            _ => None,
+        }
+    }
+
+    fn on_point(&mut self, _pt: DVec3) -> CmdResult {
+        CmdResult::NeedPoint
+    }
+
+    fn on_enter(&mut self) -> CmdResult {
+        self.show(true)
+    }
+
+    fn on_escape(&mut self) -> CmdResult {
+        CmdResult::Cancel
+    }
+
+    fn on_preview_wires(&mut self, _pt: DVec3) -> Vec<WireModel> {
+        // ponytail: the overlay is cloned per frame; cache it in the scene if
+        // comparisons of very large drawings stutter.
+        self.comparison.overlay.clone()
+    }
+}
+
+inventory::submit!(crate::command::CommandRegistration { names: &["COMPARE"] });
diff --git a/src/modules/manage/mod.rs b/src/modules/manage/mod.rs
index 48fda655e..7c7f3a7f0 100644
--- a/src/modules/manage/mod.rs
+++ b/src/modules/manage/mod.rs
@@ -2,6 +2,7 @@
 
 mod about;
 mod audit;
+pub mod compare;
 mod cui_export;
 mod cui_import;
 mod find_nonpurgeable;
diff --git a/src/scene/compare.rs b/src/scene/compare.rs
new file mode 100644
index 000000000..dd18ef101
--- /dev/null
+++ b/src/scene/compare.rs
@@ -0,0 +1,151 @@
+//! COMPARE: what differs between this drawing and another one. Objects are
+//! matched by what they draw — type, layer and their tessellated geometry —
+//! so a copy that kept its geometry matches whatever its handle, and an
+//! object that moved or changed shows as removed in one place and added in
+//! the other.
+
+use codec::{CadDocument, Handle};
+use glam::DVec3;
+use rustc_hash::FxHashMap;
+
+use crate::scene::{Scene, WireModel};
+
+/// The result of a comparison, ready to draw over the current drawing.
+pub struct Comparison {
+    /// Objects only this drawing has.
+    pub added: usize,
+    /// Objects only the other drawing has.
+    pub removed: usize,
+    /// Their outlines: added in green, removed in red.
+    pub overlay: Vec<WireModel>,
+    /// Each difference's extent, in reading order, to step through.
+    pub spots: Vec<(DVec3, DVec3)>,
+}
+
+const ADDED: [f32; 4] = [0.25, 0.85, 0.35, 1.0];
+const REMOVED: [f32; 4] = [0.95, 0.3, 0.25, 1.0];
+
+fn wires_by_entity(scene: &Scene) -> FxHashMap<Handle, Vec<WireModel>> {
+    let mut map: FxHashMap<Handle, Vec<WireModel>> = FxHashMap::default();
+    for wire in scene.entity_wires().iter() {
+        if let Some(handle) = Scene::handle_from_wire_name(&wire.name) {
+            map.entry(handle).or_default().push(wire.clone());
+        }
+    }
+    map
+}
+
+fn point(wire: &WireModel, index: usize) -> DVec3 {
+    let high = wire.points[index];
+    let low = wire.points_low.get(index).copied().unwrap_or([0.0; 3]);
+    DVec3::new(
+        f64::from(high[0]) + f64::from(low[0]),
+        f64::from(high[1]) + f64::from(low[1]),
+        f64::from(high[2]) + f64::from(low[2]),
+    )
+}
+
+/// What an object draws, as a comparable key: its type, its layer and its
+/// outline points rounded to 1e-4 drawing units.
+fn signature(document: &CadDocument, handle: Handle, wires: &[WireModel]) -> String {
+    let mut key = match document.get_entity(handle) {
+        Some(entity) => format!(
+            "{}|{}",
+            crate::entities::names::ui_name(entity),
+            entity.common().layer
+        ),
+        None => String::new(),
+    };
+    for wire in wires {
+        key.push('#');
+        for index in 0..wire.points.len() {
+            let p = point(wire, index);
+            if !p.is_finite() {
+                key.push('/');
+                continue;
+            }
+            let q = (p * 1e4).round();
+            key.push_str(&format!("{},{},{};", q.x, q.y, q.z));
+        }
+    }
+    key
+}
+
+fn extent(wires: &[WireModel]) -> Option<(DVec3, DVec3)> {
+    let mut bounds: Option<(DVec3, DVec3)> = None;
+    for wire in wires {
+        for index in 0..wire.points.len() {
+            let p = point(wire, index);
+            if !p.is_finite() {
+                continue;
+            }
+            bounds = Some(match bounds {
+                None => (p, p),
+                Some((min, max)) => (min.min(p), max.max(p)),
+            });
+        }
+    }
+    bounds
+}
+
+/// Compare `current` with the drawing `other`, in the space `current`
+/// shows.
+pub fn compare(current: &Scene, other: CadDocument) -> Comparison {
+    let mut other_scene = Scene::new();
+    other_scene.document = other;
+    other_scene.bump_geometry();
+    let here = wires_by_entity(current);
+    let there = wires_by_entity(&other_scene);
+
+    let mut unmatched: FxHashMap<String, Vec<Handle>> = FxHashMap::default();
+    for (handle, wires) in &there {
+        unmatched
+            .entry(signature(&other_scene.document, *handle, wires))
+            .or_default()
+            .push(*handle);
+    }
+    let mut overlay = Vec::new();
+    let mut spots = Vec::new();
+    let mut added = 0;
+    let mut mark = |wires: &[WireModel], color: [f32; 4]| {
+        if let Some(bounds) = extent(wires) {
+            spots.push(bounds);
+        }
+        overlay.extend(wires.iter().cloned().map(|mut wire| {
+            wire.color = color;
+            wire.selected = false;
+            wire.line_weight_px = wire.line_weight_px.max(2.0);
+            wire
+        }));
+    };
+    for (handle, wires) in &here {
+        let key = signature(&current.document, *handle, wires);
+        match unmatched.get_mut(&key).and_then(Vec::pop) {
+            Some(_) => {}
+            None => {
+                added += 1;
+                mark(wires, ADDED);
+            }
+        }
+    }
+    let mut removed = 0;
+    for handle in unmatched.into_values().flatten() {
+        if let Some(wires) = there.get(&handle) {
+            removed += 1;
+            mark(wires, REMOVED);
+        }
+    }
+    // Reading order: top to bottom, then left to right.
+    spots.sort_by(|a, b| {
+        b.1.y
+            .partial_cmp(&a.1.y)
+            .unwrap_or(std::cmp::Ordering::Equal)
+            .then(a.0.x.partial_cmp(&b.0.x).unwrap_or(std::cmp::Ordering::Equal))
+    });
+    Comparison {
+        added,
+        removed,
+        overlay,
+        spots,
+    }
+}
diff --git a/src/scene/mod.rs b/src/scene/mod.rs
index 4546c5fe7..8f19519e2 100644
--- a/src/scene/mod.rs
+++ b/src/scene/mod.rs
@@ -7,6 +7,7 @@
 //   cache   — block-definition and property caches
 pub mod annotative;
 pub mod assoc_array;
+pub mod compare;
 pub mod block_service;
 pub mod cache;
 pub mod convert;