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Mask mode replaces PII with placeholders before sending to the upstream AI service. The response is automatically unmasked before returning to you.

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How It Works

1

Request arrives

Your app sends: "Write a follow-up email to Dr. Sarah Chen (sarah.chen@hospital.org)"
2

PII detected

PasteGuard finds: Dr. Sarah Chen (PERSON), sarah.chen@hospital.org (EMAIL)
3

Masked request sent

The provider receives: "Write a follow-up email to [[PERSON_1]] ([[EMAIL_ADDRESS_1]])"
4

Response masked

The provider responds: "Dear [[PERSON_1]], Following up on our discussion..."
5

Response unmasked

You receive: "Dear Dr. Sarah Chen, Following up on our discussion..."

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When to Use

  • Simple setup without local infrastructure
  • Want to use cloud AI services while protecting PII

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Configuration

mode: mask

providers:
  openai:
    base_url: https://api.openai.com/v1

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Masking Options

masking:
  show_markers: false
  marker_text: "[protected]"
  allowlist:
    - pattern: "Company Name Inc."
    - pattern: 'TEST-\d+'
      regex: true
  denylist:
    - pattern: "ProjectX"
      type: PROJECT_NAME
    - pattern: 'CUST-\d{6}'
      type: CUSTOMER_ID
      regex: true
OptionDefaultDescription
show_markersfalseAdd visual markers around unmasked values
marker_text[protected]Marker text if enabled
allowlist[]Text patterns that are never masked; set regex: true for regex patterns
denylist[]Text patterns masked with the configured type; set regex: true for regex patterns

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Response Headers

Mask mode sets these headers on responses: 
X-PasteGuard-Mode: mask
X-PasteGuard-Provider: openai
X-PasteGuard-PII-Detected: true
X-PasteGuard-PII-Masked: true

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Streaming Support

Mask mode supports streaming responses. PasteGuard buffers tokens and unmasks placeholders in real-time as they arrive. 
stream = client.chat.completions.create(
    model="gpt-5.2",
    messages=[{"role": "user", "content": "Email Dr. Sarah Chen at sarah.chen@hospital.org"}],
    stream=True
)

for chunk in stream:
    # PII is already unmasked in each chunk
    print(chunk.choices[0].delta.content, end="")