> ## Documentation Index
> Fetch the complete documentation index at: https://cloudinary.com/documentation/llms.txt
> Use this file to discover all available pages before exploring further.

# When might underscores in public IDs or folder names cause errors?


Using underscores in a public ID containing slashes or in folder names (in fixed-folder mode) can sometimes create ambiguity and result in broken URLs on your website. For example, if you have a path in the public_ID (or a folder in fixed folder mode) such as `u_2/band_photo`, Cloudinary may misinterpret that as a transformation requesting to [underlay](transformation_reference#u_underlay) an asset named `"2"` under a base asset with public ID `favorite_band`.

To prevent such issues, consider following at least one of these best practices:

- Avoid using **underscores (`_`)** in the first few characters of public ID paths containing slashes (or in folder names in fixed-folder mode). Instead, use **hyphens (`-`)** as delimiters or ensure that at least **four** characters precede the first underscore, e.g., `abcd_1234`.
- Use [versioning](advanced_url_delivery_options#asset_versions) to separate the public ID path from the transformation section.