Quick reference
| Setting | Value / behavior |
|---|---|
| Engine | browser JavaScript |
| Time limit | one second |
| Match limit | 500 |
How to use the result
A regular expression describes a pattern to search for in text. Enter the pattern without enclosing slashes and provide flags separately. For example, \b[A-Z][a-z]+\b with g finds capitalized words in the sample. The worker adds g if it is absent so that multiple matches can be listed. Results include the matched string, the zero-based UTF-16 index, positional captures and named captures when present. This is the JavaScript regex dialect used by your browser.
Limits and interpretation
Some patterns can take excessive time on specially shaped input due to backtracking. The tester runs in a separate worker and terminates that worker after one second. It returns at most 500 matches and limits input to two million characters. An empty match advances by a code unit, or by a code point in Unicode mode, to avoid an endless loop. This local time limit is not evidence that a regex is safe for a public server. Evaluate worst-case behavior separately before placing a pattern on an untrusted request path.
Check against your destination
Run the supplied example first, then replace it with a representative input from your own workflow. Change one parameter at a time so the effect is easy to inspect. Copy or download the output and compare it with a small known case before using it in a larger system. A successful calculation establishes only the behavior described on this page; it cannot check the assumptions or access rules of a remote application. Errors are shown next to the workspace rather than silently returning an empty success.
Local processing and data handling
This tool runs in the browser and does not transmit the entered content to a processing service. No input is saved to local storage, added to the URL or synchronized to an account. The clear control removes the current field and displayed result from this page. Clipboard contents and downloaded files remain under your operating system’s control. Keep original inputs when exact byte preservation matters, and avoid including sensitive tokens or private text in screenshots that you later share.
Frequently asked questions
Does the tool contact my server?
No. It processes the provided input locally and does not execute commands on your systems.
Can I download the result?
Yes. Use the Download result control after a successful run.
What happens to my input?
It remains in this page until cleared or closed. It is not saved by the tool.
About this tool
Built and maintained by Mihai at Void Fabric. This page documents the behavior of the current implementation. Found an error or an unclear assumption? Send a reproducible example with sensitive values removed.
Reference: Void Fabric field notes · Testing and editorial policy