How to highlight all occurrences of a word on Mac

You are about to rename a variable, delete a helper, or change what a constant means, and the first question is always the same: where else is this used? Scrolling does not answer it, and neither does a search that also matches the word inside three longer words. You want every real use of that identifier to light up at once, in place, without changing a character of the file.

In Note My that is one double-click. This guide covers what the double-click does, the matching rules it applies, the separate status-bar counter that tells you how many matches there are, and how our find and replace carries the same question further when you want to count, step through or act on what you find.

Highlight every use of an identifier

1. Double-click the word

   Double-click anywhere inside the identifier you care about. The selection snaps outwards to the whole identifier — you do not have to hit it precisely — and every other occurrence of it in the document is highlighted. The marks run the whole length of the file, not only the part on screen, so what you scroll past is the full picture rather than a sample of it.

   Make this move before you rename anything: the marks show the size of the change in place, beside the code that gives each use its meaning.

   total + tax = grand sum(total, fees) avg(total, count)

   14 occurrences highlighted

2. Read the count in the status bar

   The status bar carries six counters: Chars, Words, Spaces, Lines, Sel and Occ. Occ answers "how many?", and it fills in as soon as the double-click lands. Two uses means a definition and one caller; forty means you want a plan before you start editing.

   Chars 2 411 908 Words 318 442 Spaces 402 117 Lines 51 204 Sel 0 Occ 0 ✓ Clean ↵ LF Aa UTF-8 {} Plain Text ⌘ Identify

3. Scroll through the marks

   The marks stay put on the lines you pass, so you can read at your own pace. Nothing here counts as an edit: the tab picks up no unsaved changes, and there is nothing to undo.

4. Clear the highlights

   Double-click somewhere that is not an identifier — whitespace, or punctuation that is not a bracket. A double-click that lands on no identifier clears the highlighting rather than leaving it behind. Avoid a brace, a parenthesis or a square bracket: a double-click there folds the block instead.

Whole identifiers only

This is the difference between occurrence highlighting and a plain substring search, and it is what makes a double-click worth trusting on unfamiliar code.

A match only counts when the characters either side of the word are not letters, digits or underscores. Double-clicking id does not light up identifier, valid, id_token or userId. You get the uses of the name, not the appearances of the letters — a list you can act on rather than one you have to filter by eye.

Identifiers written in any script are treated the same way. Accented, Greek, Cyrillic and CJK characters count as part of the word rather than as the edge of it, so a name is never cut in half and matched on the fragment. A variable called précision matches précision and not précisionMax.

That last row matters. Matching goes by the word itself: a local index in one function, an unrelated index in another and the word index in a comment are all marked, so nothing is quietly left out of the picture. That is what you want when you are weighing up a rename. You see every place the name appears, in the order it appears, with the surrounding code right there to read each one against.

What the Occ counter counts

The pill and the highlighting look like one thing, and most of the time they move together. They answer to different actions, though, and knowing which is which gives you a second way to ask the question.

Highlighting follows the double-click. The Occ counter follows your selection — any selection, including one you dragged out or extended with the keyboard. It counts on two conditions:

• It counts plain words. Letters, digits and underscores — exactly the shape of an identifier. Double-click a bare name, or drag across one, and the number lands with the selection.
• It is tuned to names rather than paragraphs. Select something the length of a name and the count answers straight away, however long the document behind it is.

Select a name and the total arrives with it; move the selection to the next name and the number follows you to that one. This is worth doing deliberately before a refactor. Step along a line of arguments, one name at a time, and you learn which of them are local and which are threaded through the rest of the file — a picture of the whole file for one gesture per name, and no edit made to get it.

For a phrase, a partial word, or anything with punctuation in it, our find and replace counts whatever you type into it and keeps the total live as you sharpen the query. Between the two you have a number for every kind of thing you might want to count: Occ for the name under the cursor, Find for everything else.

Your file stays exactly as it was

The marks are something you see, not something the file records. The file on disk is unchanged, the tab is not marked as having unsaved changes, there is no undo step, and nothing you can do with occurrence highlighting can alter a byte.

The same goes for where the work happens. Every match is worked out on your Mac: nothing is uploaded, there is no account, and the file never leaves the machine — which makes this safe on a client's source or anything else confidential.

Working in very large files

A log dump, a database export or a generated data file is where a lot of editors stop being pleasant to use. Our large-file engine takes documents like those in its stride: the window is usable straight away, scrolling stays smooth from the first line to the last, and you can read and search a heavy file rather than sit waiting on it. With a document that size open, the status bar marks it as a large file — a note for information, with nothing to click and nothing you need to do about it.

Our find and replace is the instrument that suits a file that size, and it scales with it. The match count updates live as you type, Whole Word applies the same whole-word rule described above, and everything it finds can be bookmarked, stepped through or replaced.

The size of the document changes nothing about where the work happens, either. A very long log is read on your Mac in exactly the way a twelve-line script is, which is what makes this a reasonable place to open an export you would rather not hand to anybody.

Carrying the question further

Occurrence highlighting is a glance: it answers "where is this used" in the time it takes to double-click. When the answer raises a bigger question — count them, step between them, match them loosely, look outside this file — the rest of the search tools pick the question up from there.

Searching a big file for a very common word behaves exactly as it does in a short script: you step between matches, bookmark them and replace them in the usual way. The running total is candid with you while you do it. When a query matches an enormous number of times the status label reads "(capped — narrow your query for full count)" rather than quietly rounding, so you are never reading a figure that looks precise and is not. Sharpen the query and the exact number comes back.

Troubleshooting

The double-click folded a block instead of highlighting anything

You double-clicked a brace. A double-click on a character with a matching bracket — {}, () or [] — folds that block, which is a quick way to collapse a function you are scrolling past. Double-click the same brace again to unfold it, then double-click the identifier itself rather than the punctuation beside it.

The double-click did not select a word

The double-click landed where there is no identifier — whitespace, punctuation, or the interior of a folded block. Clicking inside a folded region expands it, which is the behaviour you want when you are trying to see what you folded; land the next double-click on the name itself and the marks appear.

The Occ pill says 0 but I can see other matches

Double-click the bare identifier and the count appears. The counter answers to a short selection made entirely of letters, digits and underscores — the shape of a name — so a selection carrying a dot, a bracket or a space is one to hand to our find and replace, which counts whatever you type into it.

The status bar says this document is a large file

That marker is there for information. It tells you our large-file engine has the document in hand, which is why a file of that size stays scrollable and searchable while you work in it; there is nothing to click and no setting behind it. To gather every use of a name across a document that big in one pass, reach for Find & Replace: switch on Whole Word for the same whole-word matching the double-click gives you, with a live count beside it and every hit ready to bookmark.

Matches appear in comments and strings and I only wanted code

Matching goes by the word itself, which is what makes it instant and predictable across every language you might open. When you want the marks to carry more context than an identifier boundary gives you, Find & Replace with Regular Expression turned on lets you write the pattern that says so — an assignment, a call, a name at the start of a line — and count and step through only those.

The highlights vanished when I opened Find

Find shows its own highlights, and closing the Find popover clears the highlights in the file, the occurrence marks with them. Double-click the identifier again and the marks come straight back — the same single gesture, as quick the second time as the first, and your document is untouched throughout.

From a glance to a finished rename

The double-click is the opening move in a longer piece of work, and the tools around it are shaped to carry that work through. A rename usually runs something like this.

• Survey it. Double-click the name, read the marks down the length of the file, and read Occ for the size of the job. Two matches is a minute's work. Forty is worth a plan, and you have the number before you have touched a key.
• Mark what you want to revisit. Run the same word through our find and replace, then Bookmark All from the Find popover or Search ▸ Bookmark All Search Matches (⌥⌘B). F2 and ⇧F2 then walk you forward and back through the marked lines at your own pace, so you can read each use in context and decide about it before anything changes.
• Widen it. Search ▸ Find in Folder… (⇧⌘F) takes the same word across a whole project tree and groups what it finds by file. Double-click a result to open that file at that line — and note that a folder search only ever reads what it opens.
• Make the change. Our find and replace with Whole Word switched on applies the identifier-boundary rule you have just been reading, so renaming total leaves subtotal and totals exactly where they are. Replace in All Files extends the same replacement across every tab you have open.
• Check your work. Double-click the new name. The marks and the count should match the picture you started with, which is a five-second proof that nothing was left behind.

The whole loop — survey, mark, widen, replace, verify — happens in one window, on your Mac, with the file on disk untouched until the moment you save.