diff --git a/website/build.py b/website/build.py
index b19d65b..a2bf34a 100644
--- a/website/build.py
+++ b/website/build.py
@@ -243,29 +243,42 @@ def extract_entries(
     categories: list[dict],
     groups: list[dict],
 ) -> list[dict]:
-    """Flatten categories into individual library entries for table display."""
+    """Flatten categories into individual library entries for table display.
+
+    Entries appearing in multiple categories are merged into a single entry
+    with lists of categories and groups.
+    """
     cat_to_group: dict[str, str] = {}
     for group in groups:
         for cat in group["categories"]:
             cat_to_group[cat["name"]] = group["name"]
 
+    seen: dict[str, dict] = {}  # url -> entry
     entries: list[dict] = []
     for cat in categories:
         group_name = cat_to_group.get(cat["name"], "Other")
         for entry in cat["entries"]:
-            entries.append(
-                {
+            url = entry["url"]
+            if url in seen:
+                existing = seen[url]
+                if cat["name"] not in existing["categories"]:
+                    existing["categories"].append(cat["name"])
+                if group_name not in existing["groups"]:
+                    existing["groups"].append(group_name)
+            else:
+                merged = {
                     "name": entry["name"],
-                    "url": entry["url"],
+                    "url": url,
                     "description": entry["description"],
-                    "category": cat["name"],
-                    "group": group_name,
+                    "categories": [cat["name"]],
+                    "groups": [group_name],
                     "stars": None,
                     "owner": None,
                     "last_commit_at": None,
                     "also_see": entry["also_see"],
                 }
-            )
+                seen[url] = merged
+                entries.append(merged)
     return entries
 
 
diff --git a/website/static/main.js b/website/static/main.js
index ed04a55..9c7b159 100644
--- a/website/static/main.js
+++ b/website/static/main.js
@@ -59,7 +59,8 @@ function applyFilters() {
 
     // Category/group filter
     if (activeFilter) {
-      show = row.dataset[activeFilter.type] === activeFilter.value;
+      var attr = activeFilter.type === 'cat' ? row.dataset.cats : row.dataset.groups;
+      show = attr ? attr.split('||').indexOf(activeFilter.value) !== -1 : false;
     }
 
     // Text search
diff --git a/website/templates/index.html b/website/templates/index.html
index 8569016..9e8b25d 100644
--- a/website/templates/index.html
+++ b/website/templates/index.html
@@ -84,8 +84,8 @@
       <tr
         class="row"
         role="button"
-        data-cat="{{ entry.category }}"
-        data-group="{{ entry.group }}"
+        data-cats="{{ entry.categories | join('||') }}"
+        data-groups="{{ entry.groups | join('||') }}"
         tabindex="0"
         aria-expanded="false"
         aria-controls="expand-{{ loop.index }}"
@@ -116,11 +116,13 @@
           >{% else %}&mdash;{% endif %}
         </td>
         <td class="col-cat">
-          <button class="tag" data-type="cat" data-value="{{ entry.category }}">
-            {{ entry.category }}
+          {% for cat in entry.categories %}
+          <button class="tag" data-type="cat" data-value="{{ cat }}">
+            {{ cat }}
           </button>
-          <button class="tag tag-group" data-type="group" data-value="{{ entry.group }}">
-            {{ entry.group }}
+          {% endfor %}
+          <button class="tag tag-group" data-type="group" data-value="{{ entry.groups[0] }}">
+            {{ entry.groups[0] }}
           </button>
         </td>
         <td class="col-arrow"><span class="arrow">&rarr;</span></td>