Put it to work
Use (?<name>\w+)@(?<domain>[\w.]+) to extract two parts of an email address.
From input to output
- Open Regex tester and load the example.
- Read the format notes, choose your options, and replace the example with your input. Start with test data instead of sensitive information.
- Run the tool and inspect the result and status. If an error appears, correct the input format and run it again.
- Copy the output or download a file. Generated and converted results are not saved automatically.
Replacement with named capture groups
Captured values can be referenced as $1 and $2. A group named with (?<name>...) is referenced as $<name>; $& means the whole match. Without g, replacement affects only the first match. Nested repetition such as (a+)+ can become extremely slow on some inputs. If execution times out, remove unnecessary nesting before trying smaller inputs.
Example input
Pattern: (?<name>\w+)@(?<domain>[\w.]+) Flags: g Text: hello@example.com Replacement: $<name> [at] $<domain>
Reading the result
hello [at] example.com
Details that matter
Format and meaning
Uses the JavaScript RegExp engine. Other languages may behave differently.
Using it correctly
g enables global matching, i ignores case, and m enables multiline anchors.
Common pitfalls
Reference captured groups with $1 or $<name> in replacement text.
Supported scope and limits
100 KB input, 1.5 second execution limit, at most 1,000 matches
Split inputs that exceed the limit. If a format or algorithm is unsupported, choose a tool that matches your requirements instead of silently changing the format.
What happens to your data?
Tools run in your browser. DNS lookup sends the queried domain to the named external provider. Ads may appear on home, guide, and workspace pages according to settings.
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