diff --git a/crates/engine/src/cmd/app_more.rs b/crates/engine/src/cmd/app_more.rs
index f607c8288..5bd897ba9 100644
--- a/crates/engine/src/cmd/app_more.rs
+++ b/crates/engine/src/cmd/app_more.rs
@@ -152,7 +152,7 @@ fn clear_recent_presets(s: &mut Session, _: &Value) -> Result<Value> {
 
 fn save_copy_xml(s: &mut Session, p: &Value) -> Result<Value> {
     let path = str_p(p, "path").ok_or_else(|| bad("file.saveCopyAsXml", "missing `path` (.ecprojx)"))?;
-    let xml = crate::xml_project::to_xml(&s.project.to_file_json_with_view(&s.saved_view())?).map_err(EngineError::Other)?;
+    let xml = crate::xml_project::to_xml(&s.project.to_file_json_with_view(&s.saved_view(), false)?).map_err(EngineError::Other)?;
     s.services.write_file(path, xml.as_bytes()).map_err(|e| EngineError::Other(format!("cannot write {path}: {e}")))?;
     s.toast(format!("Saved an XML copy to {path}"));
     Ok(json!({"path": path, "bytes": xml.len()}))
diff --git a/crates/engine/src/cmd/file.rs b/crates/engine/src/cmd/file.rs
index 194845803..beb161a53 100644
--- a/crates/engine/src/cmd/file.rs
+++ b/crates/engine/src/cmd/file.rs
@@ -87,7 +87,8 @@ pub(crate) fn open(s: &mut Session, p: &Value) -> Result<Value> {
 /// project opened from an XML copy saves as XML again). Fails, writing nothing, when the project
 /// wouldn't read back.
 pub(crate) fn file_text(s: &Session, path: &str) -> Result<String> {
-    let json = s.project.to_file_json_with_view(&s.saved_view())?;
+    let compact = s.prefs.project.compact_project_files && !crate::xml_project::is_xml_path(path);
+    let json = s.project.to_file_json_with_view(&s.saved_view(), compact)?;
     if crate::xml_project::is_xml_path(path) { crate::xml_project::to_xml(&json).map_err(EngineError::Other) } else { Ok(json) }
 }
 
diff --git a/crates/engine/src/settings/prefs/dialog.rs b/crates/engine/src/settings/prefs/dialog.rs
index e3f2006d8..d330ce190 100644
--- a/crates/engine/src/settings/prefs/dialog.rs
+++ b/crates/engine/src/settings/prefs/dialog.rs
@@ -122,6 +122,11 @@ pub fn pages() -> Vec<Page> {
                 Section("New Project"),
                 s("project.useTemplate", "New Project Loads Template", B, true),
                 s("project.templatePath", "Template Project", Kind::Path, true),
+                Section("Project Files"),
+                s("project.compactProjectFiles", "Save Compact Project Files", B, true),
+                Note(
+                    "Saves .ecproj files as compact JSON on one line: smaller and faster to save and open, but hard to read or diff in version control. Off, they are indented, one value per line.",
+                ),
                 Section("Auto-Save"),
                 s("autoSave.enabled", "Automatically Save Projects", B, true),
                 s("autoSave.intervalMinutes", "Save Every", Kind::Int(1, 240, "Minutes"), true),
diff --git a/crates/engine/src/settings/prefs/sections.rs b/crates/engine/src/settings/prefs/sections.rs
index e0bea8b85..aa683e2b8 100644
--- a/crates/engine/src/settings/prefs/sections.rs
+++ b/crates/engine/src/settings/prefs/sections.rs
@@ -62,6 +62,9 @@ page!(ProjectPrefs {
     /// Open a template project for File ▸ New ▸ New Project.
     use_template: bool = false,
     template_path: String = String::new(),
+    /// Write `.ecproj` files as compact JSON on one line (smaller, faster to save and open). Off:
+    /// indented, one value per line, so they read and diff cleanly in version control.
+    compact_project_files: bool = false,
 });
 
 page!(AutoSave {
diff --git a/crates/engine/src/tests/settings.rs b/crates/engine/src/tests/settings.rs
index 81bed3c43..03003a77b 100644
--- a/crates/engine/src/tests/settings.rs
+++ b/crates/engine/src/tests/settings.rs
@@ -389,6 +389,23 @@ fn new_project_template_and_default_renderer() {
     let _ = std::fs::remove_dir_all(d);
 }
 
+#[test]
+fn project_files_are_indented_unless_compact_is_on() {
+    let d = tmp("compact-project-files");
+    let path = d.join("p.ecproj");
+    let mut s = session_with_comp();
+    s.execute("file.saveAs", json!({"path": path.to_string_lossy()})).unwrap();
+    let pretty = std::fs::read_to_string(&path).unwrap();
+    assert!(pretty.starts_with("{\n  \"savedBy\""), "indented by default");
+    s.execute("prefs.set", json!({"key": "project.compactProjectFiles", "value": true})).unwrap();
+    s.execute("file.saveAs", json!({"path": path.to_string_lossy()})).unwrap();
+    let compact = std::fs::read_to_string(&path).unwrap();
+    assert!(!compact.contains('\n'), "one line when Save Compact Project Files is on");
+    let open = |text: &str| effectcraft_project::Project::from_json(text).unwrap();
+    assert_eq!(open(&compact), open(&pretty), "both read back as the same project");
+    let _ = std::fs::remove_dir_all(d);
+}
+
 // ---------------------------------------------------------------- shortcuts
 
 #[test]
diff --git a/crates/project/src/item.rs b/crates/project/src/item.rs
index 22759e27d..b2b64ed2c 100644
--- a/crates/project/src/item.rs
+++ b/crates/project/src/item.rs
@@ -267,10 +267,11 @@ impl Project {
     /// (NaN or infinity, written as `null`, and nesting too deep to parse) are refused on every
     /// save; debug builds also read the text back.
     pub fn to_file_json(&self) -> Result<String, ProjectError> {
-        self.to_file_json_with_view(&SavedView::default())
+        self.to_file_json_with_view(&SavedView::default(), false)
     }
-    /// [`Project::to_file_json`] that also records the open compositions ([`SavedView`]).
-    pub fn to_file_json_with_view(&self, view: &SavedView) -> Result<String, ProjectError> {
+    /// [`Project::to_file_json`] that also records the open compositions ([`SavedView`]), on one
+    /// line when `compact` (Settings ▸ Project ▸ Save Compact Project Files).
+    pub fn to_file_json_with_view(&self, view: &SavedView, compact: bool) -> Result<String, ProjectError> {
         if self.schema > SCHEMA_VERSION {
             return Err(ProjectError::Invalid(format!(
                 "the project can't be saved: it holds a value a project file can't store (project schema {} is newer than this version supports ({SCHEMA_VERSION}))",
@@ -289,7 +290,8 @@ impl Project {
         let file = File { saved_by: APP_VERSION, view, project: self };
         file_check::check(&file)
             .map_err(|e| ProjectError::Invalid(format!("the project can't be saved: it holds a value a project file can't store ({e})")))?;
-        let text = serde_json::to_string_pretty(&file).map_err(|e| ProjectError::Invalid(format!("the project can't be saved: {e}")))?;
+        let text = if compact { serde_json::to_string(&file) } else { serde_json::to_string_pretty(&file) }
+            .map_err(|e| ProjectError::Invalid(format!("the project can't be saved: {e}")))?;
         #[cfg(debug_assertions)]
         Project::from_json(&text)
             .map_err(|e| ProjectError::Invalid(format!("the project can't be saved: it holds a value a project file can't store ({e})")))?;
diff --git a/crates/project/src/tests.rs b/crates/project/src/tests.rs
index f9ee16167..c0bdb012f 100644
--- a/crates/project/src/tests.rs
+++ b/crates/project/src/tests.rs
@@ -183,7 +183,7 @@ fn project_files_refuse_newer_schemas() {
         crate::SCHEMA_VERSION
     );
     assert_eq!(p.to_file_json().unwrap_err().to_string(), expected);
-    assert_eq!(p.to_file_json_with_view(&crate::SavedView::default()).unwrap_err().to_string(), expected);
+    assert_eq!(p.to_file_json_with_view(&crate::SavedView::default(), false).unwrap_err().to_string(), expected);
 }
 
 #[test]
@@ -197,7 +197,7 @@ fn saved_files_reopen_in_pretty_and_compact_form() {
 fn project_files_remember_the_open_comps() {
     let (p, cid) = project_with_layer();
     let view = crate::SavedView { active_comp: Some(cid), open_comps: vec![cid], comp_times: [(cid, effectcraft_time::Tick(4_237_833_600))].into() };
-    let text = p.to_file_json_with_view(&view).unwrap();
+    let text = p.to_file_json_with_view(&view, false).unwrap();
     assert_eq!(crate::saved_view(&text), view);
     assert_eq!(Project::from_json(&text).unwrap(), p, "the view is not part of the project");
     // Files from before #748 have no view; a garbled one is ignored, not an error.
diff --git a/docs/preferences.md b/docs/preferences.md
index ce96da0bf..2402b9a32 100644
--- a/docs/preferences.md
+++ b/docs/preferences.md
@@ -42,6 +42,7 @@ Commands (CLI, MCP, control channel):
 - `startup.windowGraphics`: Window Graphics (`auto` / `gl`), what the desktop window draws with from the next launch. `auto` lets the platform pick (DirectX 12, Vulkan or Metal); `gl` uses OpenGL, with CPU compositing, for graphics drivers that crash with the others. A launch leaves a `launch-pending` marker in the settings folder until its window has been drawing for a few seconds (or the app quits normally before that); a launch that stops earlier (a graphics driver crashing as the window opens or as its surface is re-created) leaves the marker behind, and the next launch switches to `gl` and says so (not on macOS, which has no OpenGL backend). `WGPU_BACKEND` overrides both.
 - `project.useTemplate`: New Project Loads Template
 - `project.templatePath`: Template Project
+- `project.compactProjectFiles`: Save Compact Project Files (default off). Off: File ▸ Save writes `.ecproj` files as indented JSON, one value per line, easy to read and diff in version control. On: compact JSON on one line, smaller and faster to save and open. Either opens the same; auto-saves, XML copies and template packages are not affected.
 - `autoSave.enabled`: Automatically Save Projects
 - `autoSave.intervalMinutes`: Save Every
 - `autoSave.maxVersions`: Maximum Project Versions