How It Works

Tokenization flow

Your App → NoPII → Detect PII → Tokenize → LLM Provider
                                                          ↓
Your App ← NoPII ← Detokenize ←──────────── LLM Response

Step by step:

1. 1Request arrives - NoPII identifies your account from the LLM API key in the request.
2. 2PII detection - Message content is scanned for PII. Entities above the confidence threshold are extracted.
3. 3Tokenization - Each unique PII value is replaced with a deterministic token.
4. 4PII replacement - Original PII is replaced with wrapped tokens, e.g. [PERSON: aBcDeFgH12]
5. 5Forward to LLM - The sanitized request is sent to the LLM provider. No PII reaches the provider.
6. 6Detokenize response - Tokens in the LLM response are replaced with the original PII values.
7. 7Return to caller - Your application receives a clean response with all original data intact.

Before and after

Here's what your prompt looks like before and after NoPII processes it:

Summarize the case for John Smith, SSN 123-45-6789, who lives at 42 Oak Avenue.

Summarize the case for [PERSON: aBcDeFgH12], SSN [US_SSN: iJkLmNoPqR], who lives at [LOCATION: sTuVwXyZ34].

The case for John Smith (SSN 123-45-6789) at 42 Oak Avenue involves...

Deterministic tokenization

The same plaintext always produces the same token. This means:

• The LLM can reason about relationships ("John Smith" in message 1 is the same entity in message 5)
• Token mappings are cached per session for faster processing

Token retention

Vault tokens are not stored indefinitely. Each token has a time-to-live (TTL) that controls how long the token-to-PII mapping is retained. When a token expires, the mapping is permanently deleted. If the same PII appears in a future request after expiration, a new token is generated.

The default TTL is 1 day. Pro tier accounts can configure TTL from 1 day to permanent in the admin console. See Billing & Pricing for plan details.

Supported PII entity types

NoPII detects 11 PII entity types by default (marked default below), with additional types available that can be enabled on demand (marked available below). You can enable or disable individual types and adjust the confidence threshold in the admin console. See PII Configuration for the full reference.

This is a representative list. NoPII also includes detection for API keys, tokens, and secrets (CREDENTIAL) and enhanced street address detection (LOCATION). See PII Configuration for the full reference and configuration options.

Fail-safe architecture

NoPII never forwards unsanitized PII to an LLM. If PII protection is unavailable, the request is blocked with HTTP 503 rather than sent unprotected. See Error Handling for the full error policy.