# EPUBCheck RSC-017: parser warning in a file, how to fix it

Source: https://epubcc.com/epubcheck/rsc-017/ (updated 2026-11-04)

EPUBCheck RSC-017 is a warning message: “Warning while parsing file: ….” The parser found something questionable that does not stop it from reading the file. It is a warning: the EPUB stays valid, but the text after the colon often points at a real mistake.

- Official message (EPUBCheck 5.4.0): Warning while parsing file: %1$s
- Default severity: Warning

## Typical causes

- Constructs that are allowed but discouraged or suspicious; the text after the colon names it.
- Markup copied from web pages that relies on browser leniency.

## How to fix it

1. Read the text after the colon: EPUBCheck reports the file, the line and column, and the parser's own description of the problem.
2. Fix it if the message points at a real mistake; it does not make the EPUB invalid on its own.
3. Validate again to check that no related error was hiding behind it.

## When it's not this

A schema error that makes the file invalid is RSC-005; a file that cannot be parsed is RSC-016.

## Sources

- EPUB 3.3, §3.9 XML conformance: https://www.w3.org/TR/epub-33/#sec-xml-constraints (read 2026-11-04)

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