diff --git a/background.js b/background.js
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+++ b/background.js
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+browser.runtime.onInstalled.addListener(() => {
+  browser.contextMenus.create({
+    id: 'openInMantis',
+    title: 'Open in Mantis',
+    contexts: ['selection']
+  });
+});
+
+browser.contextMenus.onClicked.addListener(async (info) => {
+  if (info.menuItemId === 'openInMantis') {
+    let selectedText = info.selectionText;
+    if (selectedText.startsWith('#')) {
+      selectedText = selectedText.substring(1);
+    }
+    const result = await browser.storage.sync.get(['customUrl']);
+    const fixedUrl = result.customUrl || 'https://example.com/view.php?id=';
+    const completeUrl = `${fixedUrl}${selectedText}`;
+    await browser.tabs.create({ url: completeUrl });
+  }
+});
diff --git a/icon-128.png b/icon-128.png
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diff --git a/icon-16.png b/icon-16.png
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diff --git a/icon-48.png b/icon-48.png
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diff --git a/manifest.json b/manifest.json
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+++ b/manifest.json
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+{
+  "manifest_version": 2,
+  "name": "Mantis Helper",
+  "version": "1.0.0.0",
+  "permissions": ["contextMenus", "storage"],
+  "background": {
+    "scripts": ["background.js"]
+  },
+  "description": "Select a number on a website and open it in Mantis from the context menu",
+  "options_ui": {
+    "page": "options.html",
+    "open_in_tab": true
+  },
+  "icons": {
+    "16": "icon-16.png",
+    "48": "icon-48.png",
+    "128": "icon-128.png"
+  },
+  "browser_specific_settings": {
+    "gecko": {
+      "id": "mantis-helper@example.com",
+      "strict_min_version": "57.0"
+    }
+  }
+}