Illegal Characters

This document explains what the illegal characters are.

Below is a list of characters that cannot be used within filenames on Flywheel, which have been enforced by the Flywheel service since version 12.3.0. This restriction maximizes data portability and provenance, by ensuring that once data is in Flywheel, the file names are supported by all target operating systems (Linux, Mac, POSIX, Windows).

List of Illegal Characters

• :
• *
• ?
• "
• |
• <
• >
• \
• /
• Non-printable ASCII characters, e.g.:
  • Tab
  • Line Feed
  • Carriage Return
  • Vertical Tab
  • Form Feed
  • etc.

Possible Behaviors

Uploading files containing illegal filename characters can have different results that can be hard to predict but may include:

• Upload request rejected
• Illegal character sanitized to an underscore “_”
• t2* string variations have * character sanitized to “star”
• Illegal character stripped
• Illegal character replaced with percent encoded equivalent
• Other undefined behavior

For a consistent experience, it is best to not attempt uploading files with filenames containing illegal characters, otherwise results can vary for reasons that can be outside Flywheel control.

The result should never be a file in Flywheel with a filename containing an illegal character.