Transformers

Transformers are middleware for validating, enriching, and redacting events in the walkerOS pipeline. Together with Mapping, they give you full control over how events are shaped before reaching destinations.

Use cases

Use Case	Example
Validate	Ensure events match JSON Schema contracts
Enrich	Add server-side data (user segments, geo)
Redact	Remove PII before sending to destinations

Basic setup

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Available transformers

Validator

Validates events using JSON Schema:

• Format validation (WalkerOS.Event structure)
• Contract validation (entity/action business rules)
• Configurable logging for validation results

Learn more →

Configuration

These fields are available on every transformer, regardless of package. They wrap the package-specific settings field, which is documented on each transformer's page.

Property	Type	Description	More
settings	Transformer.Settings	Implementation-specific configuration
env	Transformer.Env	Environment dependencies (platform-specific)
id	string	Transformer instance identifier (defaults to transformer key)
logger	Logger.Config
before	Matcher.Next	Pre-transformer chain that runs before this transformer pushes
next	Matcher.Next	Graph wiring to the next transformer in the chain
cache	Cache.Config	Step-level cache configuration for this transformer
init	boolean	Whether to initialize immediately
disabled	boolean	Completely skip this transformer in chains
mock	Transformer.Mock	Return this value instead of calling push(). Global mock for all chains. Dev/testing only.
chainMocks	Record<string, Transformer.ChainMock>	Path-specific mock values keyed by chain path. Takes precedence over global mock. Dev/testing only.

Next steps

• Validator - JSON Schema validation
• Create your own - Custom transformer guide