# EPUBCheck HTM-025: Non-registered URI scheme type found in…

Source: https://epublab.com/epubcheck/htm-025/ (updated 2026-11-03)

EPUBCheck HTM-025 is a warning message: “Non-registered URI scheme type found in href.” A link uses a URI scheme that is not registered.

- Official message (EPUBCheck 5.4.0): Non-registered URI scheme type found in href.
- Default severity: Warning

## Typical causes

- A typo in the scheme, or an app-specific scheme.

## How to fix it

- Correct the scheme to http, https, mailto or another standard one, or remove the link.

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