# EPUBCheck RSC-029: Data URL is not allowed in this context

Source: https://epublab.com/epubcheck/rsc-029/ (updated 2026-11-03)

EPUBCheck RSC-029 is an error message: “Data URL is not allowed in this context.” A data: URL (content embedded in the URL itself) is used where EPUB does not allow it.

- Official message (EPUBCheck 5.4.0): Data URL is not allowed in this context.
- Default severity: Error

## Typical causes

- A data: URL used as a link target or as a document reading apps would navigate to.

## How to fix it

- Save the embedded content as a file in the EPUB, add it to the manifest and reference it by path.

Message text and severity: EPUBCheck (W3C, BSD-3-Clause). Explanation: EPUBLab.