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Rehydra provides several functions for anonymizing text, from simple one-off calls to reusable instances.

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anonymizer.anonymize()

The primary method on an Anonymizer instance.

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Signature

anonymize(
  text: string,
  locale?: string,
  policy?: Partial<AnonymizationPolicy>
): Promise<AnonymizationResult>

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Parameters

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text
string
required
The text to anonymize
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locale
string
Locale hint (e.g., 'de-DE', 'en-US'). Helps with semantic enrichment.
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policy
Partial<AnonymizationPolicy>
Policy override for this call. Merged with default policy.

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Returns

interface AnonymizationResult {
  anonymizedText: string;
  entities: Array<{
    type: PIIType;
    id: number;
    start: number;
    end: number;
    confidence: number;
    source: 'REGEX' | 'NER';
    gender?: 'male' | 'female' | 'neutral';
    scope?: 'city' | 'country' | 'region';
  }>;
  piiMap: {
    ciphertext: string;
    iv: string;
    authTag: string;
  };
  stats: {
    countsByType: Record<PIIType, number>;
    totalEntities: number;
    processingTimeMs: number;
    modelVersion: string;
    leakScanPassed?: boolean;
  };
}

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Example

const anonymizer = createAnonymizer({
  ner: { mode: 'quantized' }
});
await anonymizer.initialize();

const result = await anonymizer.anonymize(
  'Contact John at [email protected]',
  'en-US'
);

console.log(result.anonymizedText);
// "Contact <PII type="PERSON" id="1"/> at <PII type="EMAIL" id="1"/>"

console.log(result.entities);
// [
//   { type: 'PERSON', id: 1, start: 8, end: 12, confidence: 0.95, source: 'NER' },
//   { type: 'EMAIL', id: 1, start: 16, end: 32, confidence: 1.0, source: 'REGEX' }
// ]

console.log(result.stats);
// { totalEntities: 2, processingTimeMs: 150, ... }

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anonymize()

Standalone function for one-off anonymization (regex-only by default).

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Signature

function anonymize(
  text: string,
  locale?: string,
  policy?: Partial<AnonymizationPolicy>
): Promise<AnonymizationResult>

​
Example

import { anonymize } from 'rehydra';

const result = await anonymize('Email: [email protected]');
console.log(result.anonymizedText);
// "Email: <PII type="EMAIL" id="1"/>"
Creates a temporary anonymizer for each call. For multiple texts, use createAnonymizer() instead.

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anonymizeRegexOnly()

Fast regex-only anonymization without NER.

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Signature

function anonymizeRegexOnly(
  text: string,
  policy?: Partial<AnonymizationPolicy>
): Promise<AnonymizationResult>

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Example

import { anonymizeRegexOnly } from 'rehydra';

const result = await anonymizeRegexOnly(
  'Card: 4111111111111111, IBAN: DE89370400440532013000'
);

console.log(result.anonymizedText);
// "Card: <PII type="CREDIT_CARD" id="1"/>, IBAN: <PII type="IBAN" id="2"/>"

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Performance

FunctionTime (2K chars)
anonymizeRegexOnly()~5-10 ms
anonymize() with NER~150-200 ms

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anonymizeWithNER()

One-off anonymization with NER model.

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Signature

function anonymizeWithNER(
  text: string,
  nerConfig: Omit<NERConfig, 'mode'> & { mode?: 'standard' | 'quantized' },
  policy?: Partial<AnonymizationPolicy>
): Promise<AnonymizationResult>

​
Example

import { anonymizeWithNER } from 'rehydra';

const result = await anonymizeWithNER(
  'Hello John Smith from Acme Corp!',
  { 
    mode: 'quantized',
    onStatus: console.log 
  }
);

console.log(result.anonymizedText);
// "Hello <PII type="PERSON" id="1"/> from <PII type="ORG" id="1"/>!"
Downloads and loads the NER model on each call. For multiple texts, use createAnonymizer() instead.

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Policy Overrides

Override default policy for specific calls: 
import { createAnonymizer, PIIType } from 'rehydra';

const anonymizer = createAnonymizer({
  ner: { mode: 'quantized' }
});
await anonymizer.initialize();

// Default behavior
await anonymizer.anonymize('Email: [email protected]');

// Override for this call only
await anonymizer.anonymize('Email: [email protected]', undefined, {
  enabledTypes: new Set([PIIType.PHONE]),  // Only detect phones
  allowlistTerms: new Set(['[email protected]']),  // Ignore this email
});

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Handling Results

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Access Anonymized Text

const result = await anonymizer.anonymize(text);
console.log(result.anonymizedText);

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Check Detection Stats

if (result.stats.totalEntities === 0) {
  console.log('No PII detected');
}

console.log(`Found ${result.stats.countsByType['EMAIL'] || 0} emails`);

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Validate Output

if (!result.stats.leakScanPassed) {
  console.warn('Potential PII leak detected in output');
}