# Navigating Invalid Characters in File Names

This guide covers warnings you may encounter about "invalid characters" in file names when sending or receiving packages in FileRunner.

## What are Invalid Characters?

Invalid characters are special symbols or characters in file names that can cause problems when files are processed or extracted. These characters may include:

- Control characters (non-printable characters)
- Path separators (/, \\)
- Reserved characters (:, \*, ?, ", <, >, |)
- Unicode characters that may not be supported by all file systems
- Leading or trailing spaces in file names
- Certain special symbols depending on the operating system

## When Sending Packages

When uploading files that contain invalid characters, you’ll see a warning message that says:

Your Options

You can click on "affected files" to see exactly which files have problems. This opens a modal showing a list of problem files. You have two options:

- Remove affected files: Excludes problem files from your package (recommended)
- Keep affected files: Includes all files but limits download options for recipients

What Happens Next

- If you remove files: You'll see a confirmation message and can send the package normally
- If you keep files: Recipients will have limited download options (no quick extraction)

## When Receiving Packages

If a package contains files with invalid characters, you’ll see a warning message that says:

This warning appears to protect you from potential download failures or file corruption.

## How Download Options are Affected

When forbidden characters are detected, FileRunner automatically adjusts your download options for safety:

Available Options:

- **Save as .tar package** - Downloads the entire package as a compressed archive
- **Standard browser download** - Uses your browser's built-in download mechanism

Unavailable options:

- **Save files for quick access** - File extraction is automatically disabled

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