Find and Replace Text
The two settings that decide the answer
Case. With "ignore case" off, Delhi and delhi are different words and only one gets replaced. That is usually what you want when renaming a variable and almost never what you want when fixing prose.
Whole word. Searching for cat without it also hits
category, concatenate and scattered. Whole word requires a
boundary either side, which is what stops a rename quietly corrupting a dozen unrelated words.
When to turn regular expressions on
For anything that is a shape rather than a string — every number, every date, everything between two
markers. With them on, $1 in the replacement means the first captured group, so
(\d{4})-(\d{2}) replaced with $2/$1 turns 2026-08 into 08/2026.
With them off, every character you type is literal — a dot is a dot and a dollar sign is a dollar sign. That is the safer default for ordinary text.
Nothing leaves your browser
The text is never uploaded and no file is opened or written. Paste in, copy out. That matters because the things people bulk-replace are usually logs, exports and drafts.
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Frequently Asked Questions
No. Nothing is opened or written — you paste text in, the result appears beside it, and you copy what you want. Nothing is uploaded either, which matters when the text is a log or a document you have not published.
It stops a search for "cat" matching inside "category" or "concatenate". It works by requiring a word boundary either side, so it will not help with a phrase that already contains punctuation.
Yes. The text is treated as one block, so a search containing a line break works. With regular expressions on, use \\n for a newline.
With regular expressions on, $1 is the first capture group, $2 the second, and $& the whole match. Without them the replacement is inserted literally, so a $ is just a dollar sign.
Usually case. "Delhi" and "delhi" are different unless you turn off case sensitivity. A trailing space in the search box is the other common cause, and it is invisible.
Only what your browser can hold in memory. Very large documents will feel slow because the whole result is rebuilt on every keystroke.