# EPUBCheck RSC-029: data URL not allowed here, how to fix it

Source: https://epubcc.com/epubcheck/rsc-029/ (updated 2026-11-04)

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. EPUB 3.3 restricts data URLs so that every document a reader can navigate to is a real file in the container.

- 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.
- Content generated by a tool that inlines everything as data URLs.

## How to fix it

1. Find the data: URL named in the message.
2. Save the embedded content as a file in the EPUB, add it to the manifest and reference it by path.
3. Validate again.

## When it's not this

A file: URL pointing to a local disk is a different error, RSC-030.

## Sources

- EPUB 3.3, §3.7 Data URLs: https://www.w3.org/TR/epub-33/#sec-data-urls (read 2026-11-04)

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