{"id":28101,"date":"2025-05-13T18:40:00","date_gmt":"2025-05-13T16:40:00","guid":{"rendered":"https:\/\/www.tuttologia.com\/mac\/?p=28101"},"modified":"2025-05-13T11:54:34","modified_gmt":"2025-05-13T09:54:34","slug":"cannot-use-thunderbolt-accessory-what-it-really-means-and-what-you-can-do","status":"publish","type":"post","link":"https:\/\/www.tuttologia.com\/mac\/2025\/05\/cannot-use-thunderbolt-accessory-what-it-really-means-and-what-you-can-do\/","title":{"rendered":"\u201cCannot Use Thunderbolt Accessory\u201d: What It Really Means and What You Can Do"},"content":{"rendered":"\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"1024\" height=\"683\" src=\"https:\/\/www.tuttologia.com\/mac\/immagini-sito\/Thunderbolt-Mac-connection-1024x683.jpg\" alt=\"\u201cCannot Use Thunderbolt Accessory\u201d: What It Really Means and What You Can Do\" class=\"wp-image-28102\" srcset=\"https:\/\/www.tuttologia.com\/mac\/immagini-sito\/Thunderbolt-Mac-connection-1024x683.jpg 1024w, https:\/\/www.tuttologia.com\/mac\/immagini-sito\/Thunderbolt-Mac-connection-300x200.jpg 300w, https:\/\/www.tuttologia.com\/mac\/immagini-sito\/Thunderbolt-Mac-connection-768x512.jpg 768w, https:\/\/www.tuttologia.com\/mac\/immagini-sito\/Thunderbolt-Mac-connection.jpg 1200w\" sizes=\"auto, (max-width: 1024px) 100vw, 1024px\" \/><\/figure>\n\n\n\n<p>When trying to connect two Macs via Thunderbolt or USB-C cable, users often have a clear goal: to extend the desktop, mirror the display, or use an iMac as an external monitor. But instead, they\u2019re greeted with an error message:<\/p>\n\n\n\n<p><strong>\u201cCannot Use Thunderbolt Accessory. Connect the accessory to a Thunderbolt port on this Mac.\u201d<\/strong><\/p>\n\n\n\n<p>This isn\u2019t a bug, nor is it a user error. It\u2019s a clear sign that the connection you\u2019re attempting isn\u2019t supported by your Mac\u2019s hardware or macOS.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><strong>Why this message appears<\/strong><\/h3>\n\n\n\n<p>Your Mac is trying to identify a valid Thunderbolt accessory\u2014such as a monitor, external drive, or dock. But if you connect another Mac instead (like a recent iMac), it won\u2019t recognize it as a compatible display. Specifically:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>iMacs with Apple Silicon (M1, M2, M3 chips)<\/strong>\u00a0cannot be used as external displays, neither via cable nor through Target Display Mode.<\/li>\n\n\n\n<li><strong>Intel-based iMacs from 2015 onwards<\/strong>\u00a0also no longer support Target Display Mode.<\/li>\n\n\n\n<li>The error occurs when one Mac is connected to another Mac that\u00a0<strong>cannot act as a video output device<\/strong>.<\/li>\n<\/ul>\n\n\n\n<p>This is a hardware and system limitation\u2014not a fault of the cable, nor a user mistake.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><strong>What you can do instead<\/strong><\/h3>\n\n\n\n<p>If your goal was to extend your desktop or use an iMac as a second screen, there are alternative methods that don\u2019t rely on a direct cable connection:<\/p>\n\n\n\n<h4 class=\"wp-block-heading\"><strong>1. Luna Display<\/strong><\/h4>\n\n\n\n<p>A small hardware dongle that plugs into a USB-C or HDMI port and allows you to use a second Mac (including Apple Silicon iMacs) as a wireless or wired display.<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Compatible with recent macOS versions<\/li>\n\n\n\n<li>Supports both USB-C and Wi-Fi connections<\/li>\n\n\n\n<li>Smooth performance, suitable for creative work<\/li>\n\n\n\n<li>Requires software installation on both Macs<\/li>\n<\/ul>\n\n\n\n<p>\ud83d\udd17&nbsp;<a href=\"https:\/\/astropad.com\/product\/lunadisplay\/\" target=\"_blank\" rel=\"noopener noreferrer nofollow\">Official Luna Display website<\/a><\/p>\n\n\n\n<h4 class=\"wp-block-heading\"><strong>2. Duet Display<\/strong><\/h4>\n\n\n\n<p>A software-only solution that extends your desktop to a second Mac over the network (Wi-Fi or Ethernet). The Pro version supports macOS-to-macOS connections.<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Easy to install and configure<\/li>\n\n\n\n<li>Works well on fast, stable networks<\/li>\n\n\n\n<li>Requires software on both devices<\/li>\n\n\n\n<li>Display quality depends on local network speed<\/li>\n<\/ul>\n\n\n\n<p>\ud83d\udd17&nbsp;<a href=\"https:\/\/www.duetdisplay.com\/\" target=\"_blank\" rel=\"noopener noreferrer nofollow\">Official Duet Display website<\/a><\/p>\n\n\n\n<h4 class=\"wp-block-heading\"><strong>3. Universal Control<\/strong><\/h4>\n\n\n\n<p>A built-in macOS feature introduced with&nbsp;<strong>macOS Monterey<\/strong>. It doesn\u2019t extend or mirror the display, but allows you to control multiple Macs using a single keyboard and mouse.<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>No display sharing \u2014 but files and text can be copied across devices<\/li>\n\n\n\n<li>Requires: same Apple ID, Wi-Fi and Bluetooth enabled, Handoff turned on<\/li>\n\n\n\n<li>Windows and apps remain on their respective screens<\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\"><strong>What\u2019s not possible<\/strong><\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>You cannot use an iMac with Apple Silicon as a monitor<\/strong>, via cable or otherwise<\/li>\n\n\n\n<li><strong>Target Display Mode is no longer supported<\/strong>\u00a0on macOS or by any current iMac<\/li>\n\n\n\n<li><strong>No official adapters or hacks exist<\/strong>\u00a0to enable it again<\/li>\n\n\n\n<li><strong>No free solution<\/strong>\u00a0currently allows for true screen extension between two recent Macs via cable<\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\"><strong>In summary<\/strong><\/h3>\n\n\n\n<p>When macOS displays the message \u201cCannot Use Thunderbolt Accessory,\u201d it\u2019s letting you know that the device you\u2019ve connected \u2014 most likely another Mac \u2014 cannot act as a supported Thunderbolt display. It\u2019s not a software bug or faulty cable: it\u2019s a structural limitation.<\/p>\n\n\n\n<p>To achieve a similar result,&nbsp;<strong>third-party solutions like Luna Display or Duet Display<\/strong>&nbsp;offer the best experience, and they work reliably on&nbsp;<strong>macOS Sequoia<\/strong>&nbsp;and newer systems.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity is-style-wide\"\/>\n\n\n\n<p><strong>Software mentioned in this article:<\/strong><\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><a href=\"https:\/\/astropad.com\/product\/lunadisplay\/\" target=\"_blank\" rel=\"noopener noreferrer nofollow\">Luna Display<\/a><\/li>\n\n\n\n<li><a href=\"https:\/\/www.duetdisplay.com\/\" target=\"_blank\" rel=\"noopener noreferrer nofollow\">Duet Display<\/a><\/li>\n<\/ul>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity is-style-wide\"\/>\n","protected":false},"excerpt":{"rendered":"<p>When trying to connect two Macs via Thunderbolt or USB-C cable, users often have a<\/p>\n","protected":false},"author":1,"featured_media":28102,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[2191],"tags":[2125],"class_list":["post-28101","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-mac-and-digital-life","tag-mac"],"_links":{"self":[{"href":"https:\/\/www.tuttologia.com\/mac\/wp-json\/wp\/v2\/posts\/28101","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.tuttologia.com\/mac\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.tuttologia.com\/mac\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.tuttologia.com\/mac\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.tuttologia.com\/mac\/wp-json\/wp\/v2\/comments?post=28101"}],"version-history":[{"count":1,"href":"https:\/\/www.tuttologia.com\/mac\/wp-json\/wp\/v2\/posts\/28101\/revisions"}],"predecessor-version":[{"id":28103,"href":"https:\/\/www.tuttologia.com\/mac\/wp-json\/wp\/v2\/posts\/28101\/revisions\/28103"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.tuttologia.com\/mac\/wp-json\/wp\/v2\/media\/28102"}],"wp:attachment":[{"href":"https:\/\/www.tuttologia.com\/mac\/wp-json\/wp\/v2\/media?parent=28101"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.tuttologia.com\/mac\/wp-json\/wp\/v2\/categories?post=28101"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.tuttologia.com\/mac\/wp-json\/wp\/v2\/tags?post=28101"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}