# Celery > Celery is a BSD-licensed open-source distributed task queue for Python. It runs work > asynchronously in the background across a pool of workers, using a message broker (RabbitMQ, > Redis, Amazon SQS and other Kombu transports) to carry task messages and a result backend > (Redis, RPC, database, Memcached, Cassandra, S3) to carry results. Celery is a LIBRARY, not a > hosted service: there is no HTTP API, no base URL, no account and no API key. Its public > interfaces are Python programming APIs plus a documented broker message protocol. Generated by API Evangelist on 2026-09-05 from the Celery documentation and this repository. Method: generated. Celery does not publish an llms.txt (probed https://docs.celeryq.dev/llms.txt and https://docs.celeryq.dev/en/stable/llms.txt on 2026-09-05 — both 404). ## What an agent needs to know first - There is nothing to call over the network. To use Celery an agent must be running inside a Python process that has the `celery` package installed and an app configured against a broker. - Delivery is AT-LEAST-ONCE. A task can execute more than once if a worker dies mid-execution. Celery provides no idempotency key and no replay protection; the documentation instructs developers to write idempotent task bodies. Assume duplicates. - `apply_async` / `delay` can be undone with `revoke()` BEFORE the task starts executing, or with `revoke(terminate=True)` while it is running (prefork and eventlet pools only). `purge` cannot be undone at all — the docs warn messages are permanently deleted. - Remote control and inspect commands only work on the amqp and redis brokers. ## Core interfaces - [Task API](https://docs.celeryq.dev/en/stable/userguide/tasks.html): defining and executing tasks — decorators, retries, `autoretry_for`, `retry_backoff`, time limits, rate limits, custom task classes. Reference: https://docs.celeryq.dev/en/stable/reference/celery.app.task.html - [Application API](https://docs.celeryq.dev/en/stable/userguide/application.html): configuring brokers, result backends, serialization, routing and task discovery. Reference: https://docs.celeryq.dev/en/stable/reference/celery.html — settings: https://docs.celeryq.dev/en/stable/userguide/configuration.html - [Canvas API](https://docs.celeryq.dev/en/stable/userguide/canvas.html): workflow composition — signatures, chains, groups, chords, maps, starmaps, chunks. - [Beat API](https://docs.celeryq.dev/en/stable/userguide/periodic-tasks.html): periodic tasks with crontab, interval and solar schedules. Reference: https://docs.celeryq.dev/en/stable/reference/celery.beat.html - [Worker API](https://docs.celeryq.dev/en/stable/userguide/workers.html): execution pools (prefork, gevent, eventlet, solo, threads), autoscaling, remote control, revocation. Reference: https://docs.celeryq.dev/en/stable/reference/celery.worker.html - [Result Backend API](https://docs.celeryq.dev/en/stable/userguide/tasks.html#result-backends): storing and retrieving task state and results. Reference: https://docs.celeryq.dev/en/stable/reference/celery.result.html - [Signals API](https://docs.celeryq.dev/en/stable/userguide/signals.html): task, worker, beat and consumer lifecycle hooks. Reference: https://docs.celeryq.dev/en/stable/reference/celery.signals.html - [Monitoring and Events API](https://docs.celeryq.dev/en/stable/userguide/monitoring.html): inspect/control commands and the worker event stream. Reference: https://docs.celeryq.dev/en/stable/reference/celery.events.html ## Getting started - Introduction: https://docs.celeryq.dev/en/stable/getting-started/introduction.html - Getting started: https://docs.celeryq.dev/en/stable/getting-started/ - Brokers and backends: https://docs.celeryq.dev/en/stable/getting-started/backends-and-brokers/index.html - Full documentation: https://docs.celeryq.dev/en/stable/ - API reference index: https://docs.celeryq.dev/en/stable/reference/index.html - Command line interface: https://docs.celeryq.dev/en/stable/reference/cli.html ## Contracts and semantics - Message protocol (versions 1 and 2; v2 default since 4.0): https://docs.celeryq.dev/en/stable/internals/protocol.html - Error hierarchy (`celery.exceptions`): https://docs.celeryq.dev/en/stable/reference/celery.exceptions.html - Security model — broker credentials, `accept_content` allowlist, `auth` serializer message signing: https://docs.celeryq.dev/en/stable/userguide/security.html - Deprecation time-line: https://docs.celeryq.dev/en/stable/internals/deprecation.html - Change history: https://docs.celeryq.dev/en/stable/changelog.html - Testing / eager mode / pytest fixtures: https://docs.celeryq.dev/en/stable/userguide/testing.html ## Packages - celery 5.6.3 (2026-03-26) — https://pypi.org/project/celery/ — `pip install celery` - kombu 5.6.2 (2025-12-29) — https://pypi.org/project/kombu/ - billiard 4.2.4 (2025-11-30) — https://pypi.org/project/billiard/ - vine 5.1.0 (2023-11-05) — https://pypi.org/project/vine/ - amqp 5.3.1 (2024-11-12) — https://pypi.org/project/amqp/ - django-celery-beat 2.9.0 (2026-02-28) — https://pypi.org/project/django-celery-beat/ - django-celery-results 2.6.0 (2025-04-10) — https://pypi.org/project/django-celery-results/ - pytest-celery 1.3.0 (2026-03-02) — https://pypi.org/project/pytest-celery/ ## Project - Source: https://github.com/celery/celery - Organization: https://github.com/celery - Issues: https://github.com/celery/celery/issues - Discussions: https://github.com/celery/celery/discussions - Enhancement proposals (CEPs): https://github.com/celery/ceps - Contributing: https://docs.celeryq.dev/en/stable/contributing.html - Security policy: https://github.com/celery/celery/security/policy - License (BSD-3-Clause): https://github.com/celery/celery/blob/main/LICENSE - Funding: https://opencollective.com/celery ## What Celery does not publish - No OpenAPI, Swagger, GraphQL, gRPC/Protobuf or WSDL contract — there is no network API to describe. - No AsyncAPI. The event stream in this repository (asyncapi/celery-events-asyncapi.yml) was derived by API Evangelist from the published Event Reference; it is not a provider artifact. - No /.well-known/ discovery documents, no A2A agent card, no MCP server (first-party or hosted). - No pricing, plans, sign-up, terms of service or privacy policy — it is a library, not a service. - No status page or SLA — nothing is hosted. - No security.txt; vulnerability reports go through the GitHub security policy. - The project website celeryq.dev no longer resolves and www.celeryq.dev now serves a domain parking page. Only docs.celeryq.dev (Read the Docs) is live.