> For the complete documentation index, see [llms.txt](https://docs.helmut.de/helmut4-releases/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.helmut.de/helmut4-releases/helmut4-components/helmutfx/metadata/regex-input-validation.md). # RegEx - Input Validation The **RegEx** metadata type can be used to validate and enforce that users enter a value in a specific format. For example, if a *production ID* must follow a strict rule — **one uppercase letter followed by five digits** — this metadata type can ensure that only valid IDs are accepted. The corresponding regular expression is: ``` ^[A-Z]\d{5}$ ``` This expression enforces the following: * `^` — start of the string * `[A-Z]` — exactly one uppercase letter * `\d{5}` — exactly five digits (0–9) * `$` — end of the string As a result, valid values would include `A12345` or `Z00001`, while entries such as `AA12345`, `a12345`, or `A1234` would be rejected. To configure this, a regular expression (regex) pattern must be defined.\ If you need help creating a suitable expression, you can use online generators or tools such as:\ Enter the regex pattern in the **Default Value** field. The **Value** field should remain empty. The displayed warning can be ignored.

Regex metadata

#### Limitation If a RegEx metadata type is assigned to either a **group** or a **metadata set**, the field *must always be filled with a valid value*.\ This metadata type effectively behaves as a mandatory field, because the input validation prevents saving empty or invalid values. Disabling this requirement is not possible. --- # Agent Instructions This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com. ## Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter: ``` GET https://docs.helmut.de/helmut4-releases/helmut4-components/helmutfx/metadata/regex-input-validation.md?ask=&goal= ``` `ask` is the immediate question: it should be specific, self-contained, and written in natural language. `goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.