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The core of this specification is a worker that wakes to receive events. This provides an event destination that can be used when other destinations would be inappropriate, or no other destination exists.
For example, to allow the developer to decide how a page should be fetched, an event needs to dispatch potentially before any other execution contexts exist for that origin. To react to a push message, or completion of a persistent download, the context that originally registered interest may no longer exist. In these cases, the service worker is the ideal event destination.
This specification also provides a fetch event, and a request and response store similar in design to the HTTP cache, which makes it easier to build offline-enabled web applications.
This document was published by the Web Applications Working Group as an Editor’s Draft.
Publication as an Editor’s Draft does not imply endorsement by W3C and its Members.
This is a draft document and may be updated, replaced or obsoleted by other documents at any time. It is inappropriate to cite this document as other than a work in progress.
This is a living document. Readers need to be aware that this specification may include unimplemented features, and details that may change. Service Workers 1 is a version that is advancing toward a W3C Recommendation.
This document was produced by a group operating under the W3C Patent Policy. W3C maintains a public list of any patent disclosures made in connection with the deliverables of the group; that page also includes instructions for disclosing a patent. An individual who has actual knowledge of a patent that the individual believes contains Essential Claim(s) must disclose the information in accordance with section 6 of the W3C Patent Policy.
This document is governed by the 18 August 2025 W3C Process Document.