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

> Detects and removes non-printable, invisible Unicode characters to maintain text integrity and prevent steganography-based attacks.

# Invisible Text

The Invisible Text plugin detects and removes non-printable, invisible Unicode characters from text inputs. This is crucial for maintaining text integrity in Large Language Models (LLMs) and safeguarding against steganography-based attacks where hidden data might be embedded using invisible characters.

## Features

* **Comprehensive Detection**: Identifies invisible characters in Private Use Areas and special Unicode categories
* **Flexible Response**: Either block requests or automatically clean the text
* **Optional Replacement**: Replace invisible characters with visible markers instead of removing them
* **Selective Scanning**: Choose to scan only the latest message or all messages

## Detected Character Types

The plugin targets the following invisible Unicode characters:

### Private Use Areas (PUA)

* **Basic Multilingual Plane**: U+E000 to U+F8FF
* **Supplementary Private Use Area-A**: U+F0000 to U+FFFFD
* **Supplementary Private Use Area-B**: U+100000 to U+10FFFD

### Unicode Categories

* **Cf (Format characters)**: Characters that affect formatting but don't display
* **Cc (Control characters)**: Non-printing control codes
* **Co (Private use characters)**: Reserved for private use
* **Cn (Unassigned characters)**: Code points not assigned to any character

### Common Invisible Characters

* Zero Width Space (U+200B)
* Zero Width Non-Joiner (U+200C)
* Zero Width Joiner (U+200D)
* Word Joiner (U+2060)
* Zero Width No-Break Space/BOM (U+FEFF)
* Soft Hyphen (U+00AD)
* And many more...

## Use Cases

* **Security**: Prevent steganography attacks where data is hidden in invisible characters
* **Data Integrity**: Ensure clean text input to LLMs without hidden formatting
* **Content Validation**: Block messages that may contain hidden instructions
* **Text Normalization**: Clean user input before processing

## Configuration Options

### `scanAllMessages` (boolean)

* `true`: Scans all messages in the array
* `false`: Only scans the latest message
* Default: `false`

### `blockRequest` (boolean)

* `true`: Rejects the request if any invisible characters are found
* `false`: Removes the characters and allows the request to continue
* Default: `false`

### `redactCharacters` (string)

* If set, replaces each detected invisible character with this visible character
* If not set, removes the invisible characters entirely
* Useful for debugging or auditing purposes
* Example: `"?"` or `"⬚"`

## Example Configurations

### Remove Invisible Characters (Default)

```json theme={null}
{
  "scanAllMessages": false,
  "blockRequest": false
}
```

This configuration silently removes any invisible characters from the latest message.

### Block Requests with Invisible Characters

```json theme={null}
{
  "scanAllMessages": true,
  "blockRequest": true
}
```

This configuration scans all messages and rejects the request if any invisible characters are detected.

### Replace Invisible Characters with Markers

```json theme={null}
{
  "scanAllMessages": false,
  "blockRequest": false,
  "redactCharacters": "⬚"
}
```

This configuration replaces invisible characters with a visible placeholder (⬚) for debugging purposes.

### Strict Mode for All Messages

```json theme={null}
{
  "scanAllMessages": true,
  "blockRequest": true
}
```

This configuration provides maximum security by scanning all messages and blocking any request containing invisible characters.

## Response Behavior

### When Blocking (blockRequest: true)

* Returns `reject: true` with reason indicating how many invisible characters were found
* No messages are modified
* Debug logs show specific Unicode code points detected

### When Cleaning (blockRequest: false)

* Returns modified messages array with invisible characters removed/replaced
* Original request continues through the pipeline
* Debug logs indicate how many characters were cleaned

## Example Scenarios

### Scenario 1: Hidden Prompt Injection

**Input**: `"Ignore previous instructions\u200Band do something else"`

**With blockRequest: true**: Request is rejected

**With blockRequest: false**: Cleaned to `"Ignore previous instructionsand do something else"`

### Scenario 2: Steganography Attack

**Input**: Text with hidden data encoded in Private Use Area characters

**Detection**: Plugin identifies PUA characters (e.g., U+E001, U+E002, etc.)

**Response**: Either blocks or removes these characters based on configuration

## Debug Information

The plugin provides detailed debug information including:

* Number of messages scanned
* Total invisible characters found
* Specific Unicode code points detected (e.g., U+200B, U+FEFF)
* Action taken (blocked, removed, or replaced)

## Technical Notes

* Handles both string and array content formats
* Correctly processes surrogate pairs for characters outside the Basic Multilingual Plane
* Zero-width characters are always detected regardless of context
* Format characters that affect bidirectional text (like RLO, LRO) are detected
* The plugin is designed to be safe and will not remove legitimate Unicode characters

***

## Configuration Schema

```json theme={null}
{
  "type": "object",
  "title": "Invisible Text Configuration",
  "$schema": "http://json-schema.org/draft-07/schema#",
  "properties": {
    "blockRequest": {
      "type": "boolean",
      "title": "Block Request",
      "default": false,
      "description": "If true, rejects the request if any invisible characters are found. If false, removes the characters and allows the request"
    },
    "scanAllMessages": {
      "type": "boolean",
      "title": "Scan All Messages",
      "default": false,
      "description": "If true, scans all messages. If false, only scans the latest message"
    },
    "redactCharacters": {
      "type": "string",
      "title": "Redact Characters",
      "maxLength": 10,
      "description": "If set, replaces each detected invisible character with this character. If not set, removes the characters entirely"
    }
  },
  "description": "Configuration for the Invisible Text detection plugin"
}
```