Definition
A Service Worker is a script that runs in the background in the browser, between the web page and the network. It enables advanced caching, offline functionality, and push notifications. For SEO, Service Workers present specific challenges: Googlebot can execute Service Workers, but their behavior may vary depending on the bot. A misconfigured Service Worker can serve stale cached content to search engines or block access to certain resources. Conversely, a well-designed Service Worker improves perceived performance (Core Web Vitals) by serving cached content instantly. It is crucial to test site behavior with and without Service Workers to ensure indexation is not affected.
Key Points
- Service Workers can improve Core Web Vitals via intelligent caching
- Googlebot can execute Service Workers; beware of cached content served
- Always implement a cache strategy suited to content type (network-first for dynamic content)
Practical Examples
Strategic caching for Core Web Vitals
A news site uses a Service Worker to cache critical resources (CSS, fonts, above-the-fold images), reducing LCP by 40% for returning visitors.
Indexation problem
An e-commerce site discovers its Service Worker serves cached product pages to Googlebot, preventing indexation of price and stock updates.
Frequently Asked Questions
Yes, recent Googlebot executes Service Workers. However, using a network-first strategy for HTML content is recommended to ensure Google always sees the most current version of your pages.
Service Workers run client-side and don't directly affect crawl budget. However, if they incorrectly modify responses, they can indirectly cause indexation problems.
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Last updated: 2026-02-07