diff --git a/crates/ui-egui/src/io.rs b/crates/ui-egui/src/io.rs
index 73c5da31..ecfb281b 100644
--- a/crates/ui-egui/src/io.rs
+++ b/crates/ui-egui/src/io.rs
@@ -134,12 +134,25 @@ pub(crate) fn write_named(app: &mut VectorcraftApp, path: Option<String>, name:
 }
 
 /// Where a file goes when no path was given: the suggested name on the web (a download), else the
-/// save panel's choice.
+/// save panel's choice, given the suggested name's extension when it names no file type (a name
+/// typed without one).
 fn pick_path(app: &mut VectorcraftApp, pick: &FilePick) -> Result<String, String> {
     if is_web(app) {
         return Ok(pick.name.clone());
     }
-    app.services.pick_save.as_mut().and_then(|f| f(pick)).ok_or_else(|| "cancelled".into())
+    let picked = app.services.pick_save.as_mut().and_then(|f| f(pick)).ok_or("cancelled")?;
+    Ok(with_extension(&picked, &fileio::extension(&pick.name), |_| true))
+}
+
+/// `path` as typed in a save panel: kept when it ends in `ext` or its extension names a format
+/// `keeps` takes, else with `.ext` added.
+fn with_extension(path: &str, ext: &str, keeps: impl Fn(&Format) -> bool) -> String {
+    let has = fileio::extension(path);
+    if ext.is_empty() || has.eq_ignore_ascii_case(ext) || fileio::format_for_name(path).is_some_and(keeps) {
+        path.to_string()
+    } else {
+        format!("{path}.{ext}")
+    }
 }
 
 /// The active document's file name with extension `ext`, and its folder.
@@ -172,10 +185,7 @@ pub fn remember_view(app: &mut VectorcraftApp) {
 /// A path typed in a save panel: kept when its extension names a save format (the panel's file
 /// type), else `f`'s extension is added.
 fn with_save_extension(path: &str, f: &Format) -> String {
-    match fileio::format_for_name(path) {
-        Some(g) if SAVE_FORMATS.contains(&g.id) => path.to_string(),
-        _ => format!("{path}.{}", f.extensions[0]),
-    }
+    with_extension(path, f.extensions[0], |g| SAVE_FORMATS.contains(&g.id))
 }
 
 /// Write every file of an export (one per artboard, linked images) for the destination `path`.
diff --git a/crates/ui-egui/src/lib.rs b/crates/ui-egui/src/lib.rs
index 3e168386..059e0106 100644
--- a/crates/ui-egui/src/lib.rs
+++ b/crates/ui-egui/src/lib.rs
@@ -74,6 +74,8 @@ mod tests_recovery;
 #[cfg(test)]
 mod tests_save;
 #[cfg(test)]
+mod tests_saveext;
+#[cfg(test)]
 mod tests_slices;
 #[cfg(test)]
 mod tests_svg;
diff --git a/crates/ui-egui/src/tests_saveext.rs b/crates/ui-egui/src/tests_saveext.rs
new file mode 100644
index 00000000..e1a896b6
--- /dev/null
+++ b/crates/ui-egui/src/tests_saveext.rs
@@ -0,0 +1,74 @@
+//! A name typed in a save panel without an extension gets the chosen format's: Save, Save As,
+//! Save a Copy, Export, Export Selection and other writes through a save panel.
+
+use std::cell::RefCell;
+use std::rc::Rc;
+
+use serde_json::json;
+use vectorcraft_engine::Session;
+
+use crate::{FilePick, Services, VectorcraftApp, io};
+
+type Written = Rc<RefCell<Vec<String>>>;
+
+/// An app with a document whose save panel answers `typed` and whose writer records the paths.
+fn saving_app(typed: &'static str) -> (VectorcraftApp, Written) {
+    let written = Written::default();
+    let w = written.clone();
+    let services = Services {
+        write: Some(Box::new(move |p: &str, _: &[u8]| {
+            w.borrow_mut().push(p.to_string());
+            Ok(())
+        })),
+        pick_save: Some(Box::new(move |_: &FilePick| Some(typed.to_string()))),
+        ..Default::default()
+    };
+    let mut app = VectorcraftApp::new(Session::new(), services);
+    app.run("file.new", json!({"width": 100, "height": 100})).unwrap();
+    app.run("shape.rectangle", json!({"x": 10, "y": 10, "width": 30, "height": 20})).unwrap();
+    (app, written)
+}
+
+fn last(w: &Written) -> String {
+    w.borrow().last().cloned().unwrap_or_default()
+}
+
+#[test]
+fn saves_add_the_format_extension_to_a_bare_name() {
+    let (mut app, w) = saving_app("/tmp/Untitled-1");
+    app.run("file.save", json!({})).unwrap();
+    assert_eq!(last(&w), "/tmp/Untitled-1.vectorcraft");
+    assert_eq!(app.session.active().unwrap().path.as_deref(), Some("/tmp/Untitled-1.vectorcraft"));
+    let (mut app, w) = saving_app("/tmp/copy");
+    app.run("file.saveCopy", json!({"format": "svg", "svg": {}})).unwrap();
+    assert_eq!(last(&w), "/tmp/copy.svg");
+    let (mut app, w) = saving_app("/tmp/as");
+    app.run("file.saveAs", json!({"format": "pdf", "options": {}})).unwrap();
+    assert_eq!(last(&w), "/tmp/as.pdf");
+}
+
+#[test]
+fn exports_add_the_format_extension_to_a_bare_name() {
+    let (mut app, w) = saving_app("/tmp/art");
+    io::export(&mut app, Some("png"), None, &json!({})).unwrap();
+    assert_eq!(last(&w), "/tmp/art.png");
+    app.run("select.all", json!({})).unwrap();
+    app.run("document.exportSelection", json!({})).unwrap();
+    assert_eq!(last(&w), "/tmp/art.png", "Export Selection: its default format");
+    io::save_command_output(&mut app, "document.export", "txt", json!({"format": "txt"})).unwrap();
+    assert_eq!(last(&w), "/tmp/art.txt");
+}
+
+#[test]
+fn typed_extensions_are_kept() {
+    let (mut app, w) = saving_app("/tmp/art.svg");
+    io::export(&mut app, Some("svg"), None, &json!({})).unwrap();
+    assert_eq!(last(&w), "/tmp/art.svg");
+    let (mut app, w) = saving_app("/tmp/My.Poster.SVG");
+    io::export(&mut app, Some("svg"), None, &json!({})).unwrap();
+    assert_eq!(last(&w), "/tmp/My.Poster.SVG");
+    // A dot in the name isn't an extension.
+    let (mut app, w) = saving_app("/tmp/v1.2");
+    io::export(&mut app, Some("png"), None, &json!({})).unwrap();
+    assert_eq!(last(&w), "/tmp/v1.2.png");
+}