Why 317 Pattern Recognizers Beat 30

The accuracy gap between generic and specialized PII detection tools.

February 1, 20268 min read

The Problem with Generic PII Tools

Microsoft Presidio is a solid open-source foundation for PII detection. We use it as our base. But out-of-the-box Presidio ships with approximately 30 built-in recognizers focused primarily on US formats.

When your documents contain German tax IDs, Japanese My Numbers, or Swiss AHV numbers, generic tools return empty results.

The Numbers

CapabilityMicrosoft Presidiocloak.business
Pattern recognizers~30317
Countries coveredPrimarily US70+
Entity types~20~320
Languages (NER)English by default48
Regional tax IDsFew100+

What is Missing from Default Presidio

DACH Region (Germany, Austria, Switzerland)

IdentifierPresidiocloak.business
German Steuer-IDNot includedChecksum validated
German SteuernummerNot includedAll 16 Bundesland formats
German PersonalausweisNot includedFull pattern
Austrian SVNNot included10-digit format
Swiss AHV-NummerNot included13-digit format

APAC Region

IdentifierPresidiocloak.business
Japanese My NumberNot included12-digit checksum
Korean RRNNot included13-digit format
Chinese Resident IDNot included18-digit with region
Singapore NRICNot includedLetter + digits + checksum

The Consequence: Significant Accuracy Gaps

Research on multilingual PII detection found that hybrid approaches combining regex, NLP, and transformers outperform fine-tuned NER models by 82% on multilingual PII detection tasks.

For organizations operating in Germany, Japan, or other non-English markets, this is not a minor inconvenience - it is a compliance failure.

Why More Recognizers Matter

Pattern Diversity

The German Steuernummer alone has 16 different formats, one per Bundesland. Each requires its own pattern.

Checksum Validation

Pattern matching without checksum validation produces false positives. Our recognizers include validation where applicable.

Context Boosting

Detection confidence improves with context words. Our recognizers include context words in multiple languages.

The Hybrid Approach

Pattern recognizers alone are not enough. We combine three detection methods:

MethodStrength
Regex patternsStructured identifiers (SSN, tax IDs)
NLP NERUnstructured entities (names, locations)
Transformer modelsContext-dependent detection

Key Takeaways

  • Generic tools fail outside their training data - Hybrid approaches outperform NER by 82%
  • Custom development is expensive - 1,000-2,000 hours to build comprehensive coverage
  • Checksum validation prevents false positives - Pattern matching alone is not enough
  • Context words must be multilingual - English context does not boost German detections
  • Hybrid detection outperforms single methods - Combine regex, NER, and transformers

Sources

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