# @opentelemetry/propagator-b3

> OpenTelemetry B3 propagator provides context propagation for systems that are using the B3 header format

Latest version **2.11.0** (published 2026-08-31) · Apache-2.0 license · 0 weekly downloads

## Install

```sh
npm install @opentelemetry/propagator-b3
pnpm add @opentelemetry/propagator-b3
yarn add @opentelemetry/propagator-b3
bun add @opentelemetry/propagator-b3
```

## Health

**Score 75/100 (B)** — status: active.

Positive: has types; esm support; no vulnerabilities; has provenance; recently updated; high maintenance score; high quality score.

Warnings: low downloads.

## Facts

| | |
|---|---|
| Version | 2.11.0 |
| Published | 2026-08-31 |
| First published | 2020-10-26 |
| Weekly downloads | 0 |
| License | Apache-2.0 |
| TypeScript types | bundled |
| Module format | ESM + CommonJS |
| Node | ^18.19.0 \|\| >=20.6.0 |
| Dependencies | 1 |
| Unpacked size | 115.7 KB |
| Known vulnerabilities | 0 |
| Install scripts | no |
| Provenance | attested (GitHub Actions) |
| GitHub stars | 3461 |
| Author | OpenTelemetry Authors |
| Maintainers | dyladan, pichlermarc, overbalance, npmjs-account, trentm, martinkuba |
| Keywords | opentelemetry, nodejs, tracing, profiling, monitoring, b3 |

## Links

- npm: https://www.npmjs.com/package/@opentelemetry/propagator-b3
- Repository: https://github.com/open-telemetry/opentelemetry-js
- Homepage: https://github.com/open-telemetry/opentelemetry-js/tree/main/packages/opentelemetry-propagator-b3
- Issues: https://github.com/open-telemetry/opentelemetry-js/issues
- npm.io page: https://npm.io/package/@opentelemetry/propagator-b3

## Dependencies (1)

- [@opentelemetry/core](https://npm.io/package/@opentelemetry/core.md) 2.11.0

## Recent versions

- 2.11.0 (latest) — 2026-08-31
- 2.11.0-development.0 (canary) — 2026-08-31
- 1.8.0 (next) — 2022-11-09
- 2.10.0 — 2026-07-21
- 2.9.0 — 2026-07-02
- 2.8.0 — 2026-06-11
- 2.7.1 — 2026-04-29
- 2.7.0 — 2026-04-17
- 2.6.1 — 2026-03-25
- 2.6.0 — 2026-03-03
- 2.5.1 — 2026-02-12
- 2.5.0 — 2026-01-21
- 2.4.0 — 2026-01-14
- 2.3.0 — 2026-01-08
- 2.2.0 — 2025-10-21
- … 128 more at https://npm.io/package/@opentelemetry/propagator-b3/versions

## README

# OpenTelemetry Propagator B3

[![NPM Published Version][npm-img]][npm-url]
[![Apache License][license-image]][license-image]

The OpenTelemetry b3 propagator package provides multiple propagator
implementations for systems using the b3 context format. See the
[b3 specification][b3-spec] for complete details.

## B3 Formats

Single-Header Format:

```bash
b3: {TraceId}-{SpanId}-{SamplingState}-{ParentSpanId}
```

Multi-Header Format:

```bash
X-B3-TraceId: {TraceId}
X-B3-SpanId: {SpanId}
X-B3-ParentSpanId: {ParentSpanId}
X-B3-Sampled: {SamplingState}
```

- {TraceId}

  - Required
  - Encoded as 32 or 16 lower-hex characters
  - 16 character traceIds will be converted to 32 characters by left-padding
    with 0s to conform with the [OpenTelemetry specification][otel-spec-id-format]

- {SpanId}

  - Required
  - Encoded as 16 lower-hex characters

- {ParentSpanId}

  - Optional
  - Used to support the Zipkin functionality where the client and server spans
    that make up an HTTP request share the same id
  - Not propagated by this library

- {SamplingState} - Single-header

  - Optional
  - Valid values
    - 1 - Accept
    - 0 - Deny
    - d - Debug
    - Absent - Defer sampling decision

- {SamplingState} - Multi-header

  - Optional
  - Valid values
    - 1 - Accept
    - 0 - Deny

- {Flags} - Multi-header
  - Optional
  - Debug is encoded as `X-B3-Flags`: 1. Absent or any other value can be ignored. Debug implies an accept decision, so don't also send the `X-B3-Sampled` header.

## B3 Propagation

The default `B3Propagator` implements b3 propagation according to the
[OpenTelemetry specification][otel-b3-requirements]. It extracts b3 context
from multi and single header encodings and injects context using the
single-header b3 encoding by default. The inject encoding can be changed to
multi-header via configuration. See the examples below.

### B3 Single-Header Configuration

```javascript
const api = require('@opentelemetry/api');
const { B3Propagator } = require('@opentelemetry/propagator-b3');

api.propagation.setGlobalPropagator(new B3Propagator());
```

### B3 Multi-Header Configuration

```javascript
const api = require('@opentelemetry/api');
const { B3Propagator, B3InjectEncoding } = require('@opentelemetry/propagator-b3');

api.propagation.setGlobalPropagator(
  new B3Propagator({ injectEncoding: B3InjectEncoding.MULTI_HEADER })
);
```

### B3 Single and Multi-Header Configuration

The B3Propagator always extracts both the single and multi-header b3 encodings.
If you need to inject both encodings this can accomplished using a composite
propagator.

```javascript
const api = require('@opentelemetry/api');
const { CompositePropagator } = require('@opentelemetry/core');
const { B3Propagator, B3InjectEncoding } = require('@opentelemetry/propagator-b3');
api.propagation.setGlobalPropagator(
  new CompositePropagator({
    propagators: [
      new B3Propagator(),
      new B3Propagator({ injectEncoding: B3InjectEncoding.MULTI_HEADER }),
    ],
  })
);
```

## Useful links

- For more information on OpenTelemetry, visit: <https://opentelemetry.io/>
- For more about OpenTelemetry JavaScript: <https://github.com/open-telemetry/opentelemetry-js>
- For help or feedback on this project, join us in [GitHub Discussions][discussions-url]

## License

Apache 2.0 - See [LICENSE][license-url] for more information.

[discussions-url]: https://github.com/open-telemetry/opentelemetry-js/discussions
[license-url]: https://github.com/open-telemetry/opentelemetry-js-contrib/blob/master/LICENSE
[license-image]: https://img.shields.io/badge/license-Apache_2.0-green.svg?style=flat
[npm-url]: https://www.npmjs.com/package/@opentelemetry/propagator-b3
[npm-img]: https://badge.fury.io/js/%40opentelemetry%2Fpropagator-b3.svg
[b3-spec]: https://github.com/openzipkin/b3-propagation
[otel-b3-requirements]: https://github.com/open-telemetry/opentelemetry-specification/blob/master/specification/context/api-propagators.md#b3-requirements
[otel-spec-id-format]: https://github.com/open-telemetry/opentelemetry-specification/blob/master/specification/trace/api.md#retrieving-the-traceid-and-spanid

---
_Source: https://npm.io/package/@opentelemetry/propagator-b3 · Machine-readable twin of the npm.io package page. Health data is recomputed on every publish._