diff --git a/SharepointToolbox/Services/Export/HtmlExportService.cs b/SharepointToolbox/Services/Export/HtmlExportService.cs
index 3846977..1465e6c 100644
--- a/SharepointToolbox/Services/Export/HtmlExportService.cs
+++ b/SharepointToolbox/Services/Export/HtmlExportService.cs
@@ -14,8 +14,10 @@ public class HtmlExportService
     /// <summary>
     /// Builds a self-contained HTML string from the supplied permission entries.
     /// Includes inline CSS, inline JS filter, stats cards, type badges, unique/inherited badges, and user pills.
+    /// When <paramref name="groupMembers"/> is provided, SharePoint group pills become expandable.
     /// </summary>
-    public string BuildHtml(IReadOnlyList<PermissionEntry> entries, ReportBranding? branding = null)
+    public string BuildHtml(IReadOnlyList<PermissionEntry> entries, ReportBranding? branding = null,
+        IReadOnlyDictionary<string, IReadOnlyList<ResolvedMember>>? groupMembers = null)
     {
         // Compute stats
         var totalEntries      = entries.Count;
@@ -65,6 +67,8 @@ tr:hover td { background: #fafafa; }
 /* User pills */
 .user-pill { display: inline-block; background: #e0e7ff; color: #3730a3; border-radius: 12px; padding: 2px 10px; font-size: .75rem; margin: 2px 3px 2px 0; white-space: nowrap; }
 .user-pill.external-user { background: #fff7ed; color: #9a3412; border: 1px solid #fed7aa; }
+.group-expandable { cursor: pointer; }
+.group-expandable:hover { opacity: 0.8; }
 a { color: #2563eb; text-decoration: none; }
 a:hover { text-decoration: underline; }
 ");
@@ -96,6 +100,7 @@ a:hover { text-decoration: underline; }
         sb.AppendLine("</tr></thead>");
         sb.AppendLine("<tbody>");
 
+        int grpMemIdx = 0;
         foreach (var entry in entries)
         {
             var typeCss   = ObjectTypeCss(entry.ObjectType);
@@ -106,13 +111,41 @@ a:hover { text-decoration: underline; }
             var logins = entry.UserLogins.Split(';', StringSplitOptions.RemoveEmptyEntries);
             var names  = entry.Users.Split(';', StringSplitOptions.RemoveEmptyEntries);
             var pillsBuilder = new StringBuilder();
+            var memberSubRows = new StringBuilder();
+
             for (int i = 0; i < logins.Length; i++)
             {
                 var login = logins[i].Trim();
                 var name  = i < names.Length ? names[i].Trim() : login;
                 var isExt = login.Contains("#EXT#", StringComparison.OrdinalIgnoreCase);
-                var pillCss = isExt ? "user-pill external-user" : "user-pill";
-                pillsBuilder.Append($"<span class=\"{pillCss}\" data-email=\"{HtmlEncode(login)}\">{HtmlEncode(name)}</span>");
+
+                bool isExpandableGroup = entry.PrincipalType == "SharePointGroup"
+                    && groupMembers != null
+                    && groupMembers.TryGetValue(name, out var members);
+
+                if (isExpandableGroup && groupMembers != null && groupMembers.TryGetValue(name, out var resolvedMembers))
+                {
+                    var grpId = $"grpmem{grpMemIdx}";
+                    pillsBuilder.Append($"<span class=\"user-pill group-expandable\" onclick=\"toggleGroup('{grpId}')\" data-email=\"{HtmlEncode(login)}\">{HtmlEncode(name)} &#9660;</span>");
+
+                    string memberContent;
+                    if (resolvedMembers.Count > 0)
+                    {
+                        var memberParts = resolvedMembers.Select(m => $"{HtmlEncode(m.DisplayName)} &lt;{HtmlEncode(m.Login)}&gt;");
+                        memberContent = string.Join(" &bull; ", memberParts);
+                    }
+                    else
+                    {
+                        memberContent = "<em style=\"color:#888\">members unavailable</em>";
+                    }
+                    memberSubRows.AppendLine($"<tr data-group=\"{grpId}\" style=\"display:none\"><td colspan=\"7\" style=\"padding-left:2em;font-size:.8rem;color:#555\">{memberContent}</td></tr>");
+                    grpMemIdx++;
+                }
+                else
+                {
+                    var pillCss = isExt ? "user-pill external-user" : "user-pill";
+                    pillsBuilder.Append($"<span class=\"{pillCss}\" data-email=\"{HtmlEncode(login)}\">{HtmlEncode(name)}</span>");
+                }
             }
 
             sb.AppendLine("<tr>");
@@ -124,6 +157,8 @@ a:hover { text-decoration: underline; }
             sb.AppendLine($"  <td>{HtmlEncode(entry.PermissionLevels)}</td>");
             sb.AppendLine($"  <td>{HtmlEncode(entry.GrantedThrough)}</td>");
             sb.AppendLine("</tr>");
+            if (memberSubRows.Length > 0)
+                sb.Append(memberSubRows);
         }
 
         sb.AppendLine("</tbody>");
@@ -136,8 +171,13 @@ a:hover { text-decoration: underline; }
   var input = document.getElementById('filter').value.toLowerCase();
   var rows = document.querySelectorAll('#permTable tbody tr');
   rows.forEach(function(row) {
+    if (row.hasAttribute('data-group')) return;
     row.style.display = row.textContent.toLowerCase().indexOf(input) > -1 ? '' : 'none';
   });
+}
+function toggleGroup(id) {
+  var rows = document.querySelectorAll('tr[data-group=""' + id + '""]');
+  rows.forEach(function(r) { r.style.display = r.style.display === 'none' ? '' : 'none'; });
 }");
         sb.AppendLine("</script>");
         sb.AppendLine("</body>");
@@ -149,9 +189,11 @@ a:hover { text-decoration: underline; }
     /// <summary>
     /// Writes the HTML report to the specified file path using UTF-8 without BOM.
     /// </summary>
-    public async Task WriteAsync(IReadOnlyList<PermissionEntry> entries, string filePath, CancellationToken ct, ReportBranding? branding = null)
+    public async Task WriteAsync(IReadOnlyList<PermissionEntry> entries, string filePath, CancellationToken ct,
+        ReportBranding? branding = null,
+        IReadOnlyDictionary<string, IReadOnlyList<ResolvedMember>>? groupMembers = null)
     {
-        var html = BuildHtml(entries, branding);
+        var html = BuildHtml(entries, branding, groupMembers);
         await File.WriteAllTextAsync(filePath, html, new UTF8Encoding(encoderShouldEmitUTF8Identifier: false), ct);
     }
 
@@ -168,8 +210,10 @@ a:hover { text-decoration: underline; }
     /// <summary>
     /// Builds a self-contained HTML string from simplified permission entries.
     /// Includes risk-level summary cards, color-coded rows, and simplified labels column.
+    /// When <paramref name="groupMembers"/> is provided, SharePoint group pills become expandable.
     /// </summary>
-    public string BuildHtml(IReadOnlyList<SimplifiedPermissionEntry> entries, ReportBranding? branding = null)
+    public string BuildHtml(IReadOnlyList<SimplifiedPermissionEntry> entries, ReportBranding? branding = null,
+        IReadOnlyDictionary<string, IReadOnlyList<ResolvedMember>>? groupMembers = null)
     {
         var summaries = PermissionSummaryBuilder.Build(entries);
 
@@ -222,6 +266,8 @@ a:hover { text-decoration: underline; }
     .risk-badge { display: inline-block; padding: 2px 8px; border-radius: 4px; font-size: .75rem; font-weight: 600; border: 1px solid; }
     .user-pill { display: inline-block; background: #e0e7ff; color: #3730a3; border-radius: 12px; padding: 2px 10px; font-size: .75rem; margin: 2px 3px 2px 0; white-space: nowrap; }
     .user-pill.external-user { background: #fff7ed; color: #9a3412; border: 1px solid #fed7aa; }
+    .group-expandable { cursor: pointer; }
+    .group-expandable:hover { opacity: 0.8; }
     a { color: #2563eb; text-decoration: none; }
     a:hover { text-decoration: underline; }
     ");
@@ -265,6 +311,7 @@ a:hover { text-decoration: underline; }
         sb.AppendLine("</tr></thead>");
         sb.AppendLine("<tbody>");
 
+        int grpMemIdx = 0;
         foreach (var entry in entries)
         {
             var typeCss   = ObjectTypeCss(entry.ObjectType);
@@ -275,13 +322,41 @@ a:hover { text-decoration: underline; }
             var logins = entry.UserLogins.Split(';', StringSplitOptions.RemoveEmptyEntries);
             var names  = entry.Inner.Users.Split(';', StringSplitOptions.RemoveEmptyEntries);
             var pillsBuilder = new StringBuilder();
+            var memberSubRows = new StringBuilder();
+
             for (int i = 0; i < logins.Length; i++)
             {
                 var login = logins[i].Trim();
                 var name  = i < names.Length ? names[i].Trim() : login;
                 var isExt = login.Contains("#EXT#", StringComparison.OrdinalIgnoreCase);
-                var pillCss = isExt ? "user-pill external-user" : "user-pill";
-                pillsBuilder.Append($"<span class=\"{pillCss}\" data-email=\"{HtmlEncode(login)}\">{HtmlEncode(name)}</span>");
+
+                bool isExpandableGroup = entry.Inner.PrincipalType == "SharePointGroup"
+                    && groupMembers != null
+                    && groupMembers.TryGetValue(name, out _);
+
+                if (isExpandableGroup && groupMembers != null && groupMembers.TryGetValue(name, out var resolvedMembers))
+                {
+                    var grpId = $"grpmem{grpMemIdx}";
+                    pillsBuilder.Append($"<span class=\"user-pill group-expandable\" onclick=\"toggleGroup('{grpId}')\" data-email=\"{HtmlEncode(login)}\">{HtmlEncode(name)} &#9660;</span>");
+
+                    string memberContent;
+                    if (resolvedMembers.Count > 0)
+                    {
+                        var memberParts = resolvedMembers.Select(m => $"{HtmlEncode(m.DisplayName)} &lt;{HtmlEncode(m.Login)}&gt;");
+                        memberContent = string.Join(" &bull; ", memberParts);
+                    }
+                    else
+                    {
+                        memberContent = "<em style=\"color:#888\">members unavailable</em>";
+                    }
+                    memberSubRows.AppendLine($"<tr data-group=\"{grpId}\" style=\"display:none\"><td colspan=\"9\" style=\"padding-left:2em;font-size:.8rem;color:#555\">{memberContent}</td></tr>");
+                    grpMemIdx++;
+                }
+                else
+                {
+                    var pillCss = isExt ? "user-pill external-user" : "user-pill";
+                    pillsBuilder.Append($"<span class=\"{pillCss}\" data-email=\"{HtmlEncode(login)}\">{HtmlEncode(name)}</span>");
+                }
             }
 
             sb.AppendLine("<tr>");
@@ -295,6 +370,8 @@ a:hover { text-decoration: underline; }
             sb.AppendLine($"  <td><span class=\"risk-badge\" style=\"background:{riskBg};color:{riskText};border-color:{riskBorder}\">{HtmlEncode(entry.RiskLevel.ToString())}</span></td>");
             sb.AppendLine($"  <td>{HtmlEncode(entry.GrantedThrough)}</td>");
             sb.AppendLine("</tr>");
+            if (memberSubRows.Length > 0)
+                sb.Append(memberSubRows);
         }
 
         sb.AppendLine("</tbody>");
@@ -306,8 +383,13 @@ a:hover { text-decoration: underline; }
       var input = document.getElementById('filter').value.toLowerCase();
       var rows = document.querySelectorAll('#permTable tbody tr');
       rows.forEach(function(row) {
+        if (row.hasAttribute('data-group')) return;
         row.style.display = row.textContent.toLowerCase().indexOf(input) > -1 ? '' : 'none';
       });
+    }
+    function toggleGroup(id) {
+      var rows = document.querySelectorAll('tr[data-group=""' + id + '""]');
+      rows.forEach(function(r) { r.style.display = r.style.display === 'none' ? '' : 'none'; });
     }");
         sb.AppendLine("</script>");
         sb.AppendLine("</body>");
@@ -319,9 +401,11 @@ a:hover { text-decoration: underline; }
     /// <summary>
     /// Writes the simplified HTML report to the specified file path.
     /// </summary>
-    public async Task WriteAsync(IReadOnlyList<SimplifiedPermissionEntry> entries, string filePath, CancellationToken ct, ReportBranding? branding = null)
+    public async Task WriteAsync(IReadOnlyList<SimplifiedPermissionEntry> entries, string filePath, CancellationToken ct,
+        ReportBranding? branding = null,
+        IReadOnlyDictionary<string, IReadOnlyList<ResolvedMember>>? groupMembers = null)
     {
-        var html = BuildHtml(entries, branding);
+        var html = BuildHtml(entries, branding, groupMembers);
         await File.WriteAllTextAsync(filePath, html, new UTF8Encoding(encoderShouldEmitUTF8Identifier: false), ct);
     }