Find and Replace

Two checkboxes change what your search string even means. Leave Use Regex off and every character you type is escaped before matching, so a.b finds those three literal characters and never axb. Tick it and the same string becomes a pattern. Find and Replace keeps that switch in plain sight rather than guessing from the shape of what you typed.

Matching reruns on every keystroke, with a live count on the right reading 7 matches found, or No matches when the search comes up empty. A broken pattern does not destroy your work: the result pane keeps showing the original text while a red bar reports Regex error: followed by the browser's own wording, such as Invalid regular expression: /[a-/: Unterminated character class.

Leaving Replace With blank deletes each match, which is the quickest way to strip a recurring prefix out of a list. The replacement is a single call against the string in the page, with no upload and no account.

Getting a Regex Replace Right the First Time

1. Paste the text first and leave Find empty. The result pane mirrors your input until there is something to match, which confirms the paste arrived whole.
2. Type the search string and watch the counter before you look at the output. A reading of No matches means the problem is the pattern, not the replacement.
3. Tick Use Regex only after a literal search has failed. The placeholder switches to Regex pattern e.g. \d+ as a reminder that the field is now interpreted.
4. Tick Case Sensitive when capitalisation matters. It is off by default, so error already matches ERROR unless you say otherwise.
5. Read the result, then press Copy. There is no undo and no in-place edit, and the input keeps your original text, so you can refine the pattern and try again as often as you like.

Tricky Inputs: Dollar Signs and Capture Groups

• The replacement goes straight to the browser's own replace call, so $1 inserts the first capture group and $& inserts the whole match. Writing $5 as a price works, but $1 meaning one dollar will vanish.
• Escaping applies to the pattern, never to the replacement. Even with Use Regex off, a $& typed into Replace With still expands, and $$ is how you get one literal dollar sign.
• With Replace All unticked, the counter reports the match together with each of its capture groups rather than a count of matches, so a 2-group pattern reads 3 matches found while exactly one replacement happens.
• An empty Find disables matching altogether and passes the text through, instead of matching the empty string between every character.
• The case-insensitive flag is applied in regex mode too, so an inline mode modifier is unnecessary here and unsupported by JavaScript patterns in any case.