Common questions
Where does regex101 process my test text and files?
Regex matching, replacements, unit tests, debugging, benchmarks, and file extraction run locally in your browser. Saving a workspace sends its saved contents to regex101. See privacy and local processing for the API, MCP, and sharing details.
Is there an offline app for regex101?
regex101 has an offline browser mode that uses previously cached application resources. Saving and account operations require a connection to the service. An engine or tool that is not cached cannot load offline.
Self-hosted Enterprise is a separate deployment product. Offline license validation requires a separate agreement, as described in the network guidance.
How do I prefill the interface through a URL?
Use Copy draft link for the supported current editor fields. Use a saved workspace link to share the complete workspace.
Common URL fields
The parameter reference lists supported fields, encoding rules, and how parameters work on saved-workspace links. A URL can expose its contents through browser history or shared links.
How do I link to the latest workspace version?
Replace the final version number in its access link with latest.
A numbered link keeps the selected version stable, while /latest follows later saves.
Save and share explains both choices.
How closely does regex101 match another runtime?
Select the corresponding flavor, then compare runtime version, flags, operation, and input representation. JavaScript uses the current browser's engine. Other flavors also run locally, with runtime builds supplied by regex101. The engine guide separates those choices from parser syntax support.
Why can non-ASCII results differ from PHP?
Compare the PCRE version, byte width, Unicode configuration, and actual input encoding.
A byte-oriented PHP operation and a browser editor can treat non-ASCII text differently.
The u modifier affects Unicode interpretation where supported, but it is not a universal repair for every mismatch.
The runtime troubleshooting guide explains how to reduce the difference to a reproducible case.
Are input fields unlimited?
Browser memory, execution timeouts, file extraction limits, and save request limits apply to different operations. File loading explains the supported formats and processing limits. For a rejected save, preserve a local copy before reducing the input.
Where can I get help?
The support page lists contact and community routes. Include the pattern, flags, input, and expected result in a bug report.
Is the application open source?
The regex101 application is not open source. The public issue tracker accepts problem reports. Commercial parser licensing is a separate product.