How to use Regex Tester
Enter a regular expression and flags, paste test text, then inspect matches or preview replacement output.
What the tool does
Test a regular expression against sample text, inspect matches and preview replacement output with common JavaScript flags.
Supported inputs
The code, JSON, expression or encoded text requested by the editor, using a fabricated or redacted sample rather than a live secret.
Actual output
A readable text or structured result that can be reviewed before using the available copy action.
Privacy and processing
Processing runs locally unless the tool clearly requests a public network resource.
Limitations
Complex expressions can be slow in any browser. Avoid testing untrusted patterns against extremely large text.
Common mistakes
Check that the selected input type, units and output format match the task. Do not discard the source before opening the result, and do not treat a preview, estimate or converted file as verified until you have reviewed it.
Frequently asked questions
What can I use Regex Tester for?
Test a regular expression against sample text, inspect matches and preview replacement output with common JavaScript flags.
What input does Regex Tester accept?
The code, JSON, expression or encoded text requested by the editor, using a fabricated or redacted sample rather than a live secret.
What should I check after using Regex Tester?
Complex expressions can be slow in any browser. Avoid testing untrusted patterns against extremely large text.
Related tasks and guides
- JSON Viewer — Format, validate and inspect JSON data in a readable structured view.
- URL Encoder/Decoder — Encode or decode URL components containing spaces, symbols and Unicode text.
- HTML Viewer — Preview HTML inside a sandboxed frame without running scripts.