SpanFlags represents constants used to interpret the Span.flags field, which is protobuf 'fixed32' type and is to be used as bit-fields. Each non-zero value defined in this enum is a bit-mask. To extract the bit-field, for example, use an expression like: (span.flags & SPAN_FLAGS_TRACE_FLAGS_MASK) See https://www.w3.org/TR/trace-context-2/#trace-flags for the flag definitions. Note that Span flags were introduced in version 1.1 of the OpenTelemetry protocol. Older Span producers do not set this field, consequently consumers should not rely on the absence of a particular flag bit to indicate the presence of a particular feature.