Replacing Text with Regular Expressions

The Replace mode previews substitutions using the currently selected flavor/engine (.NET, PCRE2, JavaScript, or the approximate engine for other flavors). The replacement field, live preview editor, and replacements footer fill the right panel so you always have room to read the result.

Open Replace

• Click Replace in the toolbar (or right-panel tab), or press Ctrl+2.
• Enter a replacement pattern such as [$1], ${user}, or a literal string. A short hint under the field lists common backreference forms.
• The preview updates live while the Replace tab is active. Click Preview Replace or Ctrl+Enter to force a run.
• Drag the vertical splitter between the editor and right panel if you need more width for the preview.

Backreferences

Supported forms (both engines):

Form	Meaning
$1, $2, …	Numbered capturing group
${name}	Named capturing group
$&	Entire match
\1, \2, …	Numbered group (especially useful with PCRE-style habits)
$$	Literal $

Examples with the sample email pattern (?<user>\w+)@(?<domain>\w+\.\w+):

• [$1] → [support] for support@regexcraft.com
• [${user} at ${domain}] → [support at regexcraft.com]

Preview highlighting

Substituted regions in the result are highlighted using the same match-highlight theme brush, so you can see exactly what changed.

The status area reports Replacements: N and timing.

Errors

If the pattern is invalid for the active engine, the error banner appears and the preview is cleared. Fix the pattern or switch flavor as needed.

Split (related)

Split (Ctrl+3) divides the subject on each match of the pattern:

• Numbered parts list
• Optional Remove empty entries
• Delimiter matches can be highlighted when viewing the subject after a split run

Tips

• Switch .NET ↔︎ PCRE2 to compare replacement behavior.
• Use Generate → Replace to emit the same pattern/replacement as code.
• Save useful replace workflows to the Library (pattern + subject + replacement).