diff --git a/atlas/templates/atlas/partials/_series_split_by_tag.html b/atlas/templates/atlas/partials/_series_split_by_tag.html
index 19b3f719..3dc3bb5e 100644
--- a/atlas/templates/atlas/partials/_series_split_by_tag.html
+++ b/atlas/templates/atlas/partials/_series_split_by_tag.html
@@ -1,17 +1,41 @@
 {% load django_htmx %}
-<form method="post"
-      action="{% url 'atlas:series_split_by_tag' pk=series.pk %}"
-      hx-post="{% url 'atlas:series_split_by_tag' pk=series.pk %}"
-      hx-target="#split-by-tag-result"
-      hx-swap="innerHTML">
-    {% csrf_token %}
-    <div class="input-group input-group-sm">
-        <select name="dicom_tag" class="form-select form-select-sm">
-            {% for tag_value, tag_label in split_tags %}
-                <option value="{{ tag_value }}">{{ tag_label }}</option>
-            {% endfor %}
-        </select>
-        <button type="submit" class="btn btn-outline-warning btn-sm">Split</button>
+<div id="series-split-by-tag-panel" class="d-flex flex-column gap-2">
+    <div class="d-flex flex-wrap gap-2">
+        <button type="button"
+                class="btn btn-outline-warning btn-sm"
+                hx-get="{% url 'atlas:series_split_by_tag' pk=series.pk %}?analyze=1"
+                hx-target="#series-split-by-tag-panel"
+                hx-swap="outerHTML">
+            Analyze split options
+        </button>
     </div>
-</form>
-<div id="split-by-tag-result" class="mt-2"></div>
+
+    {% if analyze_requested %}
+        {% if split_options %}
+            <form method="post"
+                  action="{% url 'atlas:series_split_by_tag' pk=series.pk %}"
+                  hx-post="{% url 'atlas:series_split_by_tag' pk=series.pk %}"
+                  hx-target="#split-by-tag-result"
+                  hx-swap="innerHTML">
+                {% csrf_token %}
+                <div class="input-group input-group-sm">
+                    <select name="dicom_tag" class="form-select form-select-sm">
+                        {% for option in split_options %}
+                            <option value="{{ option.tag_value }}">{{ option.tag_label }} ({{ option.split_count }} series)</option>
+                        {% endfor %}
+                    </select>
+                    <button type="submit" class="btn btn-outline-warning btn-sm">Split</button>
+                </div>
+            </form>
+            <p class="small text-muted mb-0">Only tags that can produce more than one output series are shown.</p>
+        {% else %}
+            <div class="alert alert-secondary mb-0 small">
+                No common split tags were found that can divide this series into multiple groups.
+            </div>
+        {% endif %}
+    {% else %}
+        <p class="small text-muted mb-0">Run analysis to detect valid split tags and estimated output series count.</p>
+    {% endif %}
+
+    <div id="split-by-tag-result"></div>
+</div>
diff --git a/atlas/views.py b/atlas/views.py
index de22d5b5..4e43c27e 100755
--- a/atlas/views.py
+++ b/atlas/views.py
@@ -10,6 +10,7 @@ from django.db import transaction
 from django.shortcuts import render, get_object_or_404, redirect
 from django import forms
 from django.utils import timezone
+from django.utils.html import escape
 from django.views.decorators.http import require_POST
 from django.views.decorators.http import require_http_methods
 from django.template.loader import render_to_string
@@ -3637,6 +3638,43 @@ SERIES_SPLIT_TAGS = [
 ]
 
 
+def _normalise_dicom_split_value(value):
+    if isinstance(value, pydicom.multival.MultiValue):
+        return ",".join(map(str, value))
+    return str(value)
+
+
+def _analyse_series_split_options(series):
+    tags = [tag_value for tag_value, _ in SERIES_SPLIT_TAGS]
+    tag_value_sets = {tag: set() for tag in tags}
+    tag_missing = {tag: False for tag in tags}
+
+    for image in series.images.iterator():
+        ds = image.get_dicom_data()
+        for tag in tags:
+            if tag in ds:
+                tag_value_sets[tag].add(_normalise_dicom_split_value(ds[tag].value))
+            else:
+                tag_missing[tag] = True
+
+    split_options = []
+    for tag_value, tag_label in SERIES_SPLIT_TAGS:
+        if tag_missing[tag_value]:
+            continue
+        split_count = len(tag_value_sets[tag_value])
+        if split_count > 1:
+            split_options.append(
+                {
+                    "tag_value": tag_value,
+                    "tag_label": tag_label,
+                    "split_count": split_count,
+                }
+            )
+
+    split_options.sort(key=lambda item: item["split_count"], reverse=True)
+    return split_options
+
+
 @login_required
 @user_is_author_or_atlas_series_checker
 def series_split_by_tag(request, pk):
@@ -3645,20 +3683,27 @@ def series_split_by_tag(request, pk):
     Scope: Atlas series authors and series checkers only (via decorator).
 
     Functionality:
-    - GET: renders a partial form with a dropdown of common DICOM tags.
+        - GET: renders a partial form and, on demand, analyzes available DICOM tags
+            to list only tags that can actually split the series.
     - POST: performs the split. The original series retains the images matching
       the first unique tag value; new series are cloned for each subsequent value.
-      On success, redirects to the series detail page.
+            On success, returns an HTMX success fragment with number of series created.
       On error (tag not found or non-DICOM images), returns an HTMX-swappable
       error message fragment.
     """
     series = get_object_or_404(Series, pk=pk)
 
     if request.method == "GET":
+        analyze_requested = request.GET.get("analyze") == "1"
+        split_options = _analyse_series_split_options(series) if analyze_requested else []
         return render(
             request,
             "atlas/partials/_series_split_by_tag.html",
-            {"series": series, "split_tags": SERIES_SPLIT_TAGS},
+            {
+            "series": series,
+            "split_options": split_options,
+            "analyze_requested": analyze_requested,
+            },
         )
 
     dicom_tag = request.POST.get("dicom_tag", "").strip()
@@ -3679,18 +3724,14 @@ def series_split_by_tag(request, pk):
         ds = image.get_dicom_data()
         if dicom_tag not in ds:
             return HttpResponse(
-                f'<div class="alert alert-danger">Tag <code>{dicom_tag}</code> not found in image {image}.</div>'
+                f'<div class="alert alert-danger">Tag <code>{escape(str(dicom_tag))}</code> not found in image {escape(str(image))}.</div>'
             )
-        val = ds[dicom_tag].value
-        if isinstance(val, pydicom.multival.MultiValue):
-            key = ",".join(map(str, val))
-        else:
-            key = str(val)
+        key = _normalise_dicom_split_value(ds[dicom_tag].value)
         image_map[key].append(image)
 
     if len(image_map) < 2:
         return HttpResponse(
-            f'<div class="alert alert-warning">Tag <code>{dicom_tag}</code> has only one unique value — no split performed.</div>'
+            f'<div class="alert alert-warning">Tag <code>{escape(str(dicom_tag))}</code> has only one unique value, so no split was performed.</div>'
         )
 
     case = list(series.case.all())
@@ -3715,7 +3756,9 @@ def series_split_by_tag(request, pk):
         dicom_tag,
         new_series_pks,
     )
-    return redirect("atlas:series_detail", pk=new_series_pks[0])
+    return HttpResponse(
+        f'<div class="alert alert-success">Split complete: <strong>{len(new_series_pks)}</strong> series created from tag <code>{escape(str(dicom_tag))}</code>.</div>'
+    )
 
 
 # Vendored in from BaseZipView