diff --git a/README.md b/README.md
index 9c3a378..7f74e9c 100644
--- a/README.md
+++ b/README.md
@@ -46,6 +46,9 @@ of previews, and one capture at full size in the Capture window.
   so it can pause, cancel and pick up again. `-library FOLDER` shows another folder of `.mcap` files;
   `-scan` scans it with the chosen model once it has loaded and exits (0, or 1 if any capture
   failed), for a scan without the UI, such as on a copy.
+- **Refresh** above the grid looks at the folder again: captures whose file was deleted leave the
+  grid, and new files are added (each capture keeps its index, as the workers, the OCR scan and Stats
+  refer to captures by index). By hand for now; File_Watcher can call `viewer_refresh` later.
 - **Stats** above the grid: what OCR found in the captures shown, by the chosen model: captures with
   text, lines, words, characters, confidence, words per capture, a year table, the captures with
   the most words (click to open) and the commonest words (click to search). `-stats` logs the same
diff --git a/check_targets.jai b/check_targets.jai
index cec6e3a..5f1229e 100644
--- a/check_targets.jai
+++ b/check_targets.jai
@@ -29,7 +29,7 @@ APP_NAME        :: "mcap";
 APP_FOLDER_NAME :: "mcap";
 GIT_BRANCH    :: "check";
 GIT_HASH      :: "-";
-VERSION       :: "0.0.0";
+VERSION       :: "0.0.1";
 BUILD_DATE    :: "-";
 DEBUG         :: true;
 COMPILE_TESTS :: true;
diff --git a/first.jai b/first.jai
index e2ffa5f..c864eac 100644
--- a/first.jai
+++ b/first.jai
@@ -8,7 +8,7 @@ APP_NAME              :: "mcap";
 APP_FOLDER_NAME       :: "mcap";
 APP_BUNDLE_IDENTIFIER :: "com.example.mcap";
 
-VERSION :: "0.0.0";
+VERSION :: "0.0.1";
 // Where everything goes: bin/, or bin-headless/ for builds made with no_crash_dialog, so automated
 // builds never write over the ones you run by hand.
 build_directory := "bin";
diff --git a/src/app/ocr_ui.jai b/src/app/ocr_ui.jai
index c06186e..71917a7 100644
--- a/src/app/ocr_ui.jai
+++ b/src/app/ocr_ui.jai
@@ -303,6 +303,7 @@ ocr_scan_start :: () {
   // Every capture without a reading by this model, in the order the grid shows them.
   for viewer.visible {
     capture := *viewer.captures[it];
+    if capture.removed  continue;
     if capture.catalog && catalog_section(capture.catalog, scan.model)  continue;
     array_add(*scan.items, .{it, copy_string(capture.path,, context.default_allocator)});
   }
diff --git a/src/app/viewer.jai b/src/app/viewer.jai
index 206c12c..b0b9fe3 100644
--- a/src/app/viewer.jai
+++ b/src/app/viewer.jai
@@ -6,6 +6,10 @@
 // When the workers have no previews to decode they load the catalog (app/catalog.jai), what search
 // and sorting need from each capture. The grid shows viewer.visible: the captures in display order,
 // newest first once the catalog is complete, and only those matching the search.
+//
+// A capture keeps its index for as long as the app runs: the workers, the OCR scan and Stats refer
+// to captures by index. Refresh (viewer_refresh) marks the files gone from the folder as removed and
+// appends the new ones.
 
 VIEWER_FOLDER           :: "D:/SnagitIndex/mcap";   // hardcoded for now; -library FOLDER shows another
 
@@ -45,6 +49,7 @@ Viewer_Capture :: struct {
   failed: bool;
   in_flight: bool;              // under viewer.mutex: queued for a worker, or being decoded
   catalog: *Catalog_Entry;      // main thread only; null until loaded
+  removed: bool;                // main thread only: its file was gone at a refresh; shown nowhere
 }
 
 // A catalog entry made off the main thread, for the main thread to put in place.
@@ -101,6 +106,7 @@ viewer: struct {
   visible_dirty := true;
   visible_rebuilt_at: Apollo_Time;
   catalog_loaded: s64;          // entries put in place, or found unreadable
+  removed_count: s64;           // captures marked removed
   catalog_generation: s64;      // counts changes to catalog entries (loading, an OCR reading stored)
   visible_generation: s64;      // counts rebuilds of visible
   sorted_by_date: bool;
@@ -195,7 +201,7 @@ viewer_worker :: (thread: *Thread) -> s64 {
         index = cast(s32) viewer.catalog_next;
         viewer.catalog_next += 1;
       }
-      if index >= 0  path = viewer.captures[index].path;   // the array no longer grows after startup
+      if index >= 0  path = viewer.captures[index].path;   // the array grows only under the mutex, and paths are never freed
       unlock(*viewer.mutex);
       if index < 0  break;   // nothing to do: wait to be woken
 
@@ -354,7 +360,9 @@ viewer_frame_gpu_work :: () {
     unlock(*viewer.mutex);
 
     capture := *viewer.captures[d.index];
-    if d.failed {
+    if capture.removed {
+      // Its file went at a refresh while it was being decoded.
+    } else if d.failed {
       capture.failed = true;
     } else if !capture.texture.handle {
       capture.texture = gpu_texture_create(d.pixels, d.width, d.height);
@@ -393,7 +401,9 @@ viewer_apply_catalog_updates :: () {
     }
   }
   if updates.count  viewer.catalog_generation += 1;
-  if updates.count && viewer.search_terms.count  viewer.visible_dirty = true;
+  // Under a search, or once sorted by date, entries arriving can move captures (after a refresh,
+  // the new ones get their dates).
+  if updates.count && (viewer.search_terms.count || viewer.sorted_by_date)  viewer.visible_dirty = true;
   if !viewer.sorted_by_date && viewer.catalog_loaded >= viewer.captures.count {
     viewer.sorted_by_date = true;
     viewer.visible_dirty = true;
@@ -404,6 +414,61 @@ viewer_apply_catalog_updates :: () {
 
 // The captures in display order: by date, newest first, once every date is known (by name until
 // then), and only those matching the search.
+// Looks at the folder again: captures whose file is gone are marked removed, and new files are
+// added, their previews and catalog entries loaded as the others' were. Indices stay as they are.
+viewer_refresh :: () {
+  start := current_time_monotonic();
+  present: Table(string, bool);   // the folder's .mcap files now
+  present.allocator = temp;
+  for file_list(viewer_folder(),, temp) {
+    if ends_with_nocase(path_filename(it), tprint(".%", MCAP_EXTENSION))  table_set(*present, it, true);
+  }
+
+  removed, added: s64;
+  known: Table(string, bool);     // the captures still there
+  known.allocator = temp;
+  for * capture, index: viewer.captures {
+    if capture.removed  continue;
+    if table_contains(*present, capture.path) { table_set(*known, capture.path, true); continue; }
+    capture.removed = true;
+    removed += 1;
+    if capture.texture.handle {
+      gpu_texture_release(*capture.texture);
+      found, position := array_find(viewer.with_texture, cast(s32) index);
+      if found  array_ordered_remove_by_index(*viewer.with_texture, position);
+    }
+    if viewer.full_index == index  viewer.full_open = false;
+  }
+
+  lock(*viewer.mutex);
+  for _, path: present {
+    if table_contains(*known, path)  continue;
+    capture := array_add(*viewer.captures);
+    capture.* = .{};
+    capture.path = copy_string(path,, context.default_allocator);
+    capture.name = copy_string(path_strip_extension(path_filename(path)),, context.default_allocator);
+    added += 1;
+  }
+  unlock(*viewer.mutex);
+  if added  signal(*viewer.wake);   // their catalog entries
+
+  viewer.removed_count += removed;
+  free(viewer.scan_error);
+  viewer.scan_error = "";
+  if !viewer_capture_count()  viewer.scan_error = sprint("No .% files in %.", MCAP_EXTENSION, viewer_folder());
+  viewer.catalog_generation += 1;
+  viewer.visible_dirty = true;
+  viewer.visible_rebuilt_at = .{};
+  log("[viewer] Refreshed %: % removed, % added, % captures, in % ms.", viewer_folder(), removed, added,
+      viewer.captures.count - viewer.removed_count, FF(to_float64_seconds(current_time_monotonic() - start) * 1000.0, 1));
+  toast_show(.Success, "% removed, % added", removed, added);
+}
+
+// The captures not removed.
+viewer_capture_count :: () -> s64 {
+  return viewer.captures.count - viewer.removed_count;
+}
+
 // Sets the search box to query and searches, as typing it would.
 viewer_set_search :: (query: string) {
   count := min(query.count, viewer.search_buffer.count - 1);
@@ -431,6 +496,7 @@ viewer_rebuild_visible :: () {
 
   array_reset_keeping_memory(*viewer.visible);
   for viewer.captures {
+    if it.removed  continue;
     if viewer.search_terms.count && !search_matches(it.catalog, viewer.search_terms)  continue;
     array_add(*viewer.visible, cast(s32) it_index);
   }
@@ -544,15 +610,20 @@ viewer_request_full :: (index: s32) {
 viewer_ui :: () { using ImGui;
   viewer_frame_gpu_work();
 
-  if viewer.scan_error { TextColored(app_theme.palette.warning, "%", viewer.scan_error); return; }
+  if viewer.scan_error {
+    TextColored(app_theme.palette.warning, "%", viewer.scan_error);
+    SameLine();
+    if Button("Refresh")  viewer_refresh();
+    return;
+  }
 
   SetNextItemWidth(min(GetContentRegionAvail().x * 0.5, 520));
   if InputTextWithHint("##search", "Search text, titles, URLs, apps, notes.  \"a phrase\"  ocr: title: url: app: note:", viewer.search_buffer.data, viewer.search_buffer.count) {
     viewer_search_changed();
   }
   SameLine();
-  if viewer.search_terms.count  Text("% of % captures", viewer.visible.count, viewer.captures.count);
-  else                          Text("% captures", viewer.captures.count);
+  if viewer.search_terms.count  Text("% of % captures", viewer.visible.count, viewer_capture_count());
+  else                          Text("% captures", viewer_capture_count());
   if viewer.catalog_loaded < viewer.captures.count {
     SameLine();
     TextColored(app_theme.palette.dim, "(loading the catalog: % of %; sorted by name until then)", viewer.catalog_loaded, viewer.captures.count);
@@ -565,6 +636,12 @@ viewer_ui :: () { using ImGui;
   if Button("OCR")  ocr_ui.window_open = !ocr_ui.window_open;
   SameLine();
   if Button("Stats")  stats_ui.window_open = !stats_ui.window_open;   // app/stats_ui.jai
+  SameLine();
+  busy := ocr_ui.thread_busy;   // a scan or a reading refers to captures by index
+  if busy  BeginDisabled();
+  if Button("Refresh")  viewer_refresh();
+  if busy  EndDisabled();
+  if IsItemHovered(.AllowWhenDisabled)  SetTooltip(ifx busy then "After the OCR scan or reading" else "Look at the folder again: drop the captures deleted, add the new ones");
   if IsItemHovered() {
     engine: *Ocr_Engine;
     if !ocr_ui.thread_busy  engine = ocr_ui.engine;   // the background thread owns it while busy