diff --git a/Cargo.lock b/Cargo.lock
index 79498923d..097361d61 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -1094,6 +1094,16 @@ name = "craft-docpath"
 version = "0.1.0"
 source = "git+https://github.com/storytold/craft-libs?rev=92d392cff132eaf53e13afff77f38b5c11b73aa0#92d392cff132eaf53e13afff77f38b5c11b73aa0"
 
+[[package]]
+name = "craft-ecproj-format"
+version = "0.1.0"
+source = "git+https://github.com/storytold/craft-libs?rev=246e8f837347ac642d6852df89e1425630111d21#246e8f837347ac642d6852df89e1425630111d21"
+dependencies = [
+ "serde",
+ "serde_json",
+ "thiserror 2.0.21",
+]
+
 [[package]]
 name = "craft-fonts-build"
 version = "0.1.0"
@@ -1783,6 +1793,7 @@ dependencies = [
 name = "effectcraft-project"
 version = "0.19.0"
 dependencies = [
+ "craft-ecproj-format",
  "effectcraft-color",
  "effectcraft-geom",
  "effectcraft-keyframe",
diff --git a/Cargo.toml b/Cargo.toml
index eae73bbca..6f8552723 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -14,6 +14,7 @@ repository = "https://github.com/storytold/effectcraft"
 craft-pdf = { git = "https://github.com/storytold/craft-libs", rev = "92d392cff132eaf53e13afff77f38b5c11b73aa0", version = "=0.1.0", default-features = false, features = ["read"] }
 craft-docpath = { version = "0.1.0", git = "https://github.com/storytold/craft-libs", rev = "92d392cff132eaf53e13afff77f38b5c11b73aa0" }
 craft-quit = { version = "0.1.0", git = "https://github.com/storytold/craft-libs", rev = "92d392cff132eaf53e13afff77f38b5c11b73aa0" }
+craft-ecproj-format = { version = "0.1.0", git = "https://github.com/storytold/craft-libs", rev = "246e8f837347ac642d6852df89e1425630111d21" }
 # craft-update: app-specific pretend versions apply to startup and manual checks.
 craft-update = { git = "https://github.com/storytold/craft-libs", version = "=0.1.0", rev = "c5a1cbfb5f9049f9270955caffb5bee5997aebf7", features = ["egui"] }
 # internal
diff --git a/crates/project/Cargo.toml b/crates/project/Cargo.toml
index 72d40db34..db11fea11 100644
--- a/crates/project/Cargo.toml
+++ b/crates/project/Cargo.toml
@@ -14,6 +14,7 @@ effectcraft-time = { workspace = true }
 effectcraft-geom = { workspace = true }
 effectcraft-color = { workspace = true }
 effectcraft-keyframe = { workspace = true }
+craft-ecproj-format = { workspace = true }
 serde = { workspace = true }
 serde_json = { workspace = true }
 thiserror = { workspace = true }
diff --git a/crates/project/src/item.rs b/crates/project/src/item.rs
index b2b64ed2c..1ef3d1f0a 100644
--- a/crates/project/src/item.rs
+++ b/crates/project/src/item.rs
@@ -272,26 +272,13 @@ impl Project {
     /// [`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}))",
-                self.schema
-            )));
-        }
-        #[derive(Serialize)]
-        struct File<'a> {
-            #[serde(rename = "savedBy")]
-            saved_by: &'a str,
-            #[serde(flatten)]
-            view: &'a SavedView,
-            #[serde(flatten)]
-            project: &'a Project,
-        }
-        let file = File { saved_by: APP_VERSION, view, project: self };
+        craft_ecproj_format::check_schema(self.schema)
+            .map_err(|e| ProjectError::Invalid(format!("the project can't be saved: it holds a value a project file can't store ({e})")))?;
+        let file = craft_ecproj_format::File::new(APP_VERSION, view, 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 = 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}")))?;
+        let text =
+            if compact { file.to_json_compact() } else { file.to_json() }.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})")))?;
@@ -312,9 +299,7 @@ impl Project {
     /// hostile file still opens, within bounds, and the user can be told what changed.
     pub fn from_json_repaired(s: &str) -> Result<(Project, Vec<String>), ProjectError> {
         let mut p: Project = serde_json::from_str(s).map_err(|e| ProjectError::Invalid(e.to_string()))?;
-        if p.schema > SCHEMA_VERSION {
-            return Err(ProjectError::Invalid(format!("project schema {} is newer than this version supports ({SCHEMA_VERSION})", p.schema)));
-        }
+        craft_ecproj_format::check_schema(p.schema).map_err(|e| ProjectError::Invalid(e.to_string()))?;
         p.fix_next_id();
         let mut notes = vec![];
         for item in p.items.values_mut() {
diff --git a/crates/project/src/settings.rs b/crates/project/src/settings.rs
index 5d3d57204..aace78cdc 100644
--- a/crates/project/src/settings.rs
+++ b/crates/project/src/settings.rs
@@ -4,7 +4,7 @@ use super::{BTreeMap, ColorSpace, Deserialize, Label, Serialize, Tick};
 /// The project file schema. 2: effects on layers without a source rectangle (shape, text)
 /// measure positions from the top-left of their comp-sized bounds (effect space), not from
 /// the layer's origin; projects from schema 1 are converted when opened (#227).
-pub const SCHEMA_VERSION: u32 = 2;
+pub use craft_ecproj_format::SCHEMA_VERSION;
 
 /// The first schema in which effect positions are in effect space (see [`SCHEMA_VERSION`]).
 pub const SCHEMA_EFFECT_SPACE: u32 = 2;
@@ -13,14 +13,7 @@ pub const SCHEMA_EFFECT_SPACE: u32 = 2;
 pub const APP_VERSION: &str = env!("CARGO_PKG_VERSION");
 
 /// The EffectCraft version that wrote a project file (its `savedBy`), when it says.
-pub fn saved_by(text: &str) -> Option<String> {
-    #[derive(Deserialize)]
-    struct Meta {
-        #[serde(rename = "savedBy", default)]
-        saved_by: Option<String>,
-    }
-    serde_json::from_str::<Meta>(text).ok()?.saved_by
-}
+pub use craft_ecproj_format::saved_by;
 
 /// The compositions that were open when a project file was saved and their current times
 /// (`activeComp`, `openComps` and `compTimes` next to `savedBy`), so it reopens where it was left
diff --git a/crates/project/src/tests.rs b/crates/project/src/tests.rs
index afd3d3f03..a3e41adb5 100644
--- a/crates/project/src/tests.rs
+++ b/crates/project/src/tests.rs
@@ -193,6 +193,22 @@ fn saved_files_reopen_in_pretty_and_compact_form() {
     assert_eq!(Project::from_json(&p.to_json_compact()).unwrap(), p, "compact JSON");
 }
 
+/// A project file read back and saved again is the same text, indented and compact (Save Compact
+/// Project Files), with its saved view.
+#[test]
+fn project_files_save_again_byte_for_byte() {
+    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() };
+    for compact in [false, true] {
+        let text = p.to_file_json_with_view(&view, compact).unwrap();
+        let prefix = if compact { "{\"savedBy\":\"" } else { "{\n  \"savedBy\": \"" };
+        assert!(text.starts_with(&format!("{prefix}{}\"", crate::APP_VERSION)), "compact {compact}: {text}");
+        assert_eq!(text.contains('\n'), !compact);
+        let again = Project::from_json(&text).unwrap().to_file_json_with_view(&crate::saved_view(&text), compact).unwrap();
+        assert_eq!(again, text, "compact {compact}");
+    }
+}
+
 #[test]
 fn project_files_remember_the_open_comps() {
     let (p, cid) = project_with_layer();