From 7cf89390d9bafdc0b3e3c4e14cdfee36086ee9bb Mon Sep 17 00:00:00 2001
From: AnnMarueW <amward@fastmail.com>
Date: Thu, 7 May 2026 13:43:04 -0700
Subject: [PATCH 1/2] optimize dropdown search

---
 .../src/utils/dropdownSearch.ts               | 51 +++++++++++--------
 1 file changed, 31 insertions(+), 20 deletions(-)

diff --git a/components/dash-core-components/src/utils/dropdownSearch.ts b/components/dash-core-components/src/utils/dropdownSearch.ts
index 7b88014a4f..079bba0290 100644
--- a/components/dash-core-components/src/utils/dropdownSearch.ts
+++ b/components/dash-core-components/src/utils/dropdownSearch.ts
@@ -23,6 +23,7 @@ export interface SanitizedOptions {
     options: DetailedOption[];
     indexes: string[];
     valueSet: Set<OptionValue>;
+    search: Search;
 }
 
 // Single-pass sanitization via sanitizeOptions, plus detection of
@@ -55,38 +56,48 @@ export function sanitizeDropdownOptions(
         indexes.push('search');
     }
 
-    return {options: sanitized, indexes, valueSet};
+    // Build the search index ONCE during sanitization
+    const search = new Search('value');
+    search.searchIndex = new UnorderedSearchIndex();
+    search.indexStrategy = new AllSubstringsIndexStrategy();
+    search.tokenizer = TOKENIZER;
+
+    indexes.forEach(index => {
+        search.addIndex(index);
+    });
+
+    if (sanitized.length > 0) {
+        search.addDocuments(sanitized);
+    }
+
+    return {
+        options: sanitized,
+        indexes,
+        valueSet,
+        search,
+    };
 }
 
 export function filterOptions(
     options: SanitizedOptions,
     searchValue?: string,
-    search_order?: 'index' | 'original'
+    searchOrder?: string
 ): DetailedOption[] {
     if (!searchValue) {
         return options.options;
     }
 
-    const search = new Search('value');
-    search.searchIndex = new UnorderedSearchIndex();
-    search.indexStrategy = new AllSubstringsIndexStrategy();
-    search.tokenizer = TOKENIZER;
-
-    options.indexes.forEach(index => {
-        search.addIndex(index);
-    });
+    const results =
+        (options.search.search(searchValue) as DetailedOption[]) || [];
 
-    if (options.options.length > 0) {
-        search.addDocuments(options.options);
-    }
+    // Preserve original option order
+    if (searchOrder === 'original') {
+        const resultSet = new Set(results.map(option => option.value));
 
-    const searchResults =
-        (search.search(searchValue) as DetailedOption[]) || [];
-
-    if (search_order === 'original') {
-        const resultSet = new Set(searchResults);
-        return options.options.filter(option => resultSet.has(option));
+        return options.options.filter(option =>
+            resultSet.has(option.value)
+        );
     }
 
-    return searchResults;
+    return results;
 }

From 99a1a2ae37c8e87c0f1aa6189a334f938e5d9fde Mon Sep 17 00:00:00 2001
From: AnnMarueW <amward@fastmail.com>
Date: Thu, 7 May 2026 15:13:46 -0700
Subject: [PATCH 2/2] added changelog

---
 CHANGELOG.md | 1 +
 1 file changed, 1 insertion(+)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 7bfcf40c7e..405eee0f49 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -17,6 +17,7 @@ This project adheres to [Semantic Versioning](https://semver.org/).
 - [#3723](https://github.com/plotly/dash/pull/3723) Fix misaligned `dcc.Slider` marks when some labels are empty strings
 - [#3740](https://github.com/plotly/dash/pull/3740) Fix cannot tab into dropdowns in Safari
 - [#2462](https://github.com/plotly/dash/issues/2462) Allow `MATCH` in `Input`/`State` when the callback's `Output` has no wildcards (fixed-id Output, no Output, or `ALL`-only wildcard Output). `ALLSMALLER` still requires a corresponding `MATCH` in an Output.
+- [#3768](https://github.com/plotly/dash/pull/3768) Improved `Dropdown` search performance for large options lists
 
 ## [4.1.0] - 2026-03-23