diff --git a/web/js/autocomplete.js b/web/js/autocomplete.js
index 91901fe..638cc05 100644
--- a/web/js/autocomplete.js
+++ b/web/js/autocomplete.js
@@ -5,9 +5,10 @@ import {
     getEnabledTagSourceInPriorityOrder
 } from './data.js';
 import {
-    formatCountHumanReadable,
+    isLongText,
     hiraToKata,
     kataToHira,
+    formatCountHumanReadable,
     isContainsLetterOrNumber,
     normalizeTagToInsert,
     normalizeTagToSearch,
@@ -82,8 +83,10 @@ function searchCompletionCandidates(textareaElement) {
 
     const ESCAPE_SEQUENCE = ["#", "/"]; // If the first string is that character, autocomplete will not be displayed.
     const partialTag = getCurrentPartialTag(textareaElement);
-    if (!partialTag || partialTag.length <= 0 || ESCAPE_SEQUENCE.some(seq => partialTag.startsWith(seq))) {
-        return []; // No valid input for autocomplete    
+    if (!partialTag || partialTag.length <= 0 || 
+        ESCAPE_SEQUENCE.some(seq => partialTag.startsWith(seq)) || 
+        isLongText(partialTag)) {
+        return []; // No valid input for autocomplete
     }
 
     const exactMatches = [];
diff --git a/web/js/data.js b/web/js/data.js
index 0f57bfb..cd1e4f5 100644
--- a/web/js/data.js
+++ b/web/js/data.js
@@ -1,4 +1,4 @@
-import { settingValues } from "./settings.js";
+import { settingValues, updateMaxTagLength } from "./settings.js";
 
 // --- Constants ---
 
@@ -158,6 +158,8 @@ async function loadTags(csvUrl, siteName) {
                 // Create a TagData instance instead of a plain object
                 const tagData = new TagData(tag, aliases, category, count, siteName);
 
+                updateMaxTagLength(tag.length);
+
                 autoCompleteData[siteName].sortedTags.push(tagData);
             } else {
                 console.warn(`[Autocomplete-Plus] Invalid CSV format in line ${i + 1} of ${csvUrl}: ${line}. Expected ${TAGS_CSV_HEADER_COLUMNS.length} columns, but got ${columns.length}.`);
@@ -326,7 +328,6 @@ export async function initializeData(csvListData, source) {
 
     const startTime = performance.now();
     autoCompleteData[source].isInitializing = true;
-    // console.log("[Autocomplete-Plus] Initializing autocomplete data...");
 
     try {
         // Store functions that return Promises (Promise Factories)
diff --git a/web/js/related-tags.js b/web/js/related-tags.js
index e1f779e..b68b5a8 100644
--- a/web/js/related-tags.js
+++ b/web/js/related-tags.js
@@ -1,13 +1,14 @@
-import { TagSource, TagCategory, TagData, autoCompleteData } from './data.js';
+import { TagCategory, TagData, TagSource, autoCompleteData } from './data.js';
 import { settingValues } from './settings.js';
 import {
     extractTagsFromTextArea,
     findAllTagPositions,
+    getCurrentTagRange,
     getViewportMargin,
+    isLongText,
     isValidTag,
     normalizeTagToInsert,
     normalizeTagToSearch,
-    getCurrentTagRange,
 } from './utils.js';
 
 // --- RelatedTags Logic ---
@@ -309,7 +310,7 @@ class RelatedTagsUI {
         const currentTag = getTagFromCursorPosition(textareaElement);
 
         if (!this.isPinned) {
-            if (isValidTag(currentTag)) {
+            if (!isLongText(currentTag) && isValidTag(currentTag)) {
                 this.currentTag = currentTag
             } else {
                 this.hide();
diff --git a/web/js/settings.js b/web/js/settings.js
index 6b93e98..4342852 100644
--- a/web/js/settings.js
+++ b/web/js/settings.js
@@ -17,8 +17,19 @@ export const settingValues = {
 
     // Internal logic settings
     _useFallbackAttachmentForEventListener: false, // Fallback to attach event listener when somthing goes wrong
+    _maxTagLength: 100, // Maximum tag length to prevent performance issues with long text input
 
     // Debugging settings (use internally)
     _hideWhenOutofFocus: true, // Hide UI when the input is out of focus
     _logprocessingTime: false, // Log processing time for debugging
-}
\ No newline at end of file
+}
+
+/**
+ * Update the maximum tag length setting value.
+ * This function ensures that the maximum tag length is always at least as long as the new length provided.
+ * @param {number} newLength 
+ */
+export function updateMaxTagLength(newLength) {
+    if(isNaN(newLength)) return;
+    settingValues._maxTagLength = Math.max(settingValues._maxTagLength, newLength);
+}
diff --git a/web/js/utils.js b/web/js/utils.js
index ac0246d..203fbc2 100644
--- a/web/js/utils.js
+++ b/web/js/utils.js
@@ -1,3 +1,5 @@
+import { settingValues } from './settings.js';
+
 // --- Html String constants ---
 
 /**
@@ -44,6 +46,15 @@ const REG_STRIP_TRAILING_PAREN = /(.*)(?<!\\)\)$/s;
 const REG_WILDCARD_WEIGHTED_TAG = /(\d+)[_\s]*::(.*?)(?=\||$)/g;
 const REG_WILDCARD_SIMPLE_WORD = /[^{}_|]+/g;
 
+/**
+ * Checks if the input text is longer than the maximum allowed tag length.
+ * @param {string} text The text to check.
+ * @return {boolean} True if the text is longer than the maximum tag length, false otherwise.
+ */
+export function isLongText(text) {
+    return text.length > settingValues._maxTagLength;
+}
+
 /**
  * Converts Hiragana to Katakana.
  * @param {string} str Input string.