Look Up not working on Mac? Check these four things
Nov 3, 2026 · 4 min read
Look Up on a Mac depends on a Trackpad setting, a keyboard shortcut, the sources ticked in Dictionary, and an app that hands over real text. Check them in that order. If the app never offers Look Up, LeafyApp's ⌥A box gives you the meaning from the pixels on screen.
Turn the gesture on in Trackpad settings
Open the Apple menu, then System Settings, then Trackpad in the sidebar (you may need to scroll). Under Point & Click, find Look up & data detectors and pick a gesture. Apple describes it as the gesture you use to quickly look up a word. Apple's Look Up page says the options are a tap with three fingers, or, if your trackpad supports it, force click.
If you want Force Click and it does nothing, the switch just above, Force Click and haptic feedback, has to be on too. Apple's Trackpad page says that turns on force click. A mouse has no such gesture, so on a mouse use the shortcut or Control-click.
Try Control-click and the shortcut
Two ways round the gesture. Control-click a word and choose Look Up from the menu. Apple notes that in some apps you need to select the word first. Or select the word and press ⌃⌘D: Apple's Mac keyboard shortcuts list gives it as showing or hiding the definition of the selected word. Pressed a second time, it hides the panel, which can look like it did nothing if you pressed it twice.
Select the word before pressing the shortcut. Some people rest the pointer over a word instead, but Apple's list only promises the selected word, so treat selecting as the reliable way. If the keys do nothing anywhere, check that no other utility has claimed the same combination.
Make sure a dictionary is ticked
Look Up reads from the sources chosen in the Dictionary app. In the Look Up panel, click Configure Dictionaries, or open Dictionary and choose Dictionary, then Settings. Apple's Dictionary guide says the sources ticked there decide what Dictionary shows and what Look Up uses. A word can come back empty because it is not in the ticked sources, or because Screen Time restricts it. If you just ticked a new source, wait for it to finish downloading before you search. To add more languages, see adding a dictionary to your Mac.
Why it sometimes does nothing at all
Look Up works on text the app hands to macOS as text. If what you see is a picture of words, there is no word to look up. A scan, a screenshot, a diagram label, a game menu and a subtitle burned into video are all pictures. In Preview, Photos and Safari, Live Text can turn a picture into selectable text and Look Up then works on it, as Apple's Preview page describes. Outside those apps, nothing does the conversion. The page on Live Text not working covers that side.
A scanned PDF is the usual case. Apple's page on PDFs you cannot select or copy gives two causes: the Text Selection tool is off, or the PDF is password-protected.
If nothing happens in one app
Sooner or later one app ignores Look Up while others answer. Not every app has been tested, so no list of failing apps is given. The pattern to look for is the one above: if the word will not highlight as selectable text, there is nothing for Look Up to read. If it highlights and still does nothing, the app may not pass the selection to the system. The fix then is to read the word from the screen instead.
The backup for apps that never offer it
LeafyApp does not need the app's cooperation. Press ⌥A, drag a box over the word, and macOS text recognition reads that patch of screen. You get the meaning of the word in the sentence it sits in, which a dictionary entry cannot do for a word with several senses. The word is saved with its sentence, source and date. It works on text you cannot select too, so it covers scans, subtitles and games.
It does not replace the dictionary. It answers a different question: what does this word mean here. Only the word and its sentence go out; the picture is read on your Mac and thrown away (privacy). See also looking up a word on Mac and copying text you cannot select.
Questions people ask
Why is Force Click Look Up not working on my Mac? Open System Settings, Trackpad, and check that Force Click and haptic feedback is on. Then set Look up & data detectors to the force click option. Apple says the force click choice only appears if your trackpad supports it.
Why is Control Command D not working? Apple lists ⌃⌘D as showing or hiding the definition of the selected word, so select the word first, and press it once. If it still does nothing, the app may not support Look Up, or another utility may have taken the same shortcut.
Why does the Mac dictionary not work in Chrome or in a PDF? If nothing happens in an app, first check that the word is real selectable text. In a scanned PDF it is a picture, so there is nothing to look up. LeafyApp's ⌥A box reads the pixels instead.
Look Up in a PDF is not working. What now? Apple gives two causes for a PDF that will not select in Preview: the Text Selection tool is off, or the PDF is password-protected. If the PDF is a scan, the words are a picture and need Live Text or a box-select tool.
When Look Up has nothing to read, box the word.
Free while LeafyApp is in beta. One download, macOS 14 and up.
Apple, macOS, Dictionary, Preview, Photos and Safari are trademarks of Apple Inc. LeafyApp is an independent app, not affiliated with or endorsed by Apple, and the names are used here only to describe compatibility and for comparison.