OpenZipkin B3

B3 tracing headers

B3 is a widely used tracing propagation format popularized by Zipkin. It supports both a single header and a set of multiple headers to carry the trace context.

Quick notes

64-bit and 128-bit trace IDs are both valid in B3.
x-b3-sampled and x-b3-flags communicate sampling and debug flags.
You can forward either the single header or the multi header set, not both.

B3 single header

Single header format combines trace-id, span-id, and sampling flag.

b3: 4bf92f3577b34da6a3ce929d0e0e4736-00f067aa0ba902b7-1

B3 multi headers

Multiple headers split the values for easier propagation in some systems.

x-b3-traceid: 4bf92f3577b34da6a3ce929d0e0e4736
x-b3-spanid: 00f067aa0ba902b7
x-b3-sampled: 1

Privacy note

All parsing and conversion runs locally in your browser. Nothing is sent to a server.

Spec references: B3 Propagation (single and multi header formats).

Decode B3 headers

Paste trace headers

Supports W3C traceparent, B3 (single/multi), Jaeger uber-trace-id, and Datadog headers.

Normalize hex to lowercase

Detected format: Unknown / unsupported formatPaste headers to detect the trace format.

Decoded locally in your browser. No data leaves your machine.

Spec-accurate parsing with explicit validation for flags, sampling, and ID lengths.