W3CTraceContextProtokoll

W3C Trace Context is a W3C standard that defines how to propagate distributed tracing information across process boundaries. It specifies two HTTP headers, traceparent and tracestate, that accompany requests as they traverse services, enabling traceability across systems.

traceparent provides the core linkage of a trace. Its value follows the format version-traceid-parentid-flags, with version typically 01. The trace-id is a 32-hex-character identifier that uniquely identifies the whole trace. The parent-id is a 16-hex-character identifier for the current span within the trace. The trace-flags field encodes flags such as sampling decisions. The header is intended to be opaque to the application and should be passed unchanged between services.

tracestate carries vendor-specific tracing data that supplements traceparent. It consists of a list of key=value pairs separated by commas. Each key should be unique within a tracestate; values are opaque to the standard and may be used by vendors to convey unpublished information about spans. The header is optional and should be treated as an opaque data carrier. Ordering and length constraints may apply depending on implementations.

Background and scope: the standard emerged from W3C efforts to standardize trace propagation and is designed to be technology and language agnostic, enabling interoperable tracing across different backends and runtimes. Adoption includes major tracing ecosystems and observability platforms, with support in OpenTelemetry and many tracing libraries.

Security and privacy: since these headers traverse network boundaries, they can leak internal identifiers or policy information. Do not place sensitive data in trace identifiers or tracestate values, and sanitize inputs. Implementers should validate and limit header size and handle malformed values gracefully.

Relation to other formats: Trace Context aims for broad interoperability and is often considered alongside platform-specific formats such as B3. While some vendors still support older formats, the standard provides a common baseline for cross-system tracing.