G25 — Chapter 7 - Technical SEO

Criterion G25 : Service Worker — guide + checklist

PART 1 - Fundamentals Chapter 7 - Technical SEO Keyword : service worker

This criterion is subtle… until it blocks SEO performance.

The **G25 — Service Worker** criterion is part of our SEO checklist (335 criteria). Here, you have a **practical** method to check and fix it — with a concrete example.

What exactly this criterion covers

This criterion is subtle… until it blocks SEO performance.

**G25 — Service Worker** (Chapter 7 - Technical SEO): PWA and offline cache for performance and engagement

Why it matters (SEO + UX)

Why it matters: it is a technical quality factor (crawl, rendering, indexing). When poorly applied, we often observe: ambiguity (wrong associated query), duplication between pages, or loss of performance on indexing rate.

On volume-generated sites, this criterion also acts as a **safeguard**: a stable rule prevents 1,000 errors at once.

How to check (step by step)

Approach: browser-side control (render + code). Recommended tool: **curl (headers)**.

  1. Open the page in Chrome → DevTools → Performance/Network tab.
  2. Run PageSpeed Insights and note the main weak point.
  3. Check if the problem repeats on “money” pages.

Tip: first isolate 10 “representative” URLs (top pages + generated pages) before scaling the fix.

How to fix properly

Strategy: fix + add a safeguard for bulk import.

  • Fix the biggest cost source (images, JS, fonts, cache).
  • Retest, then apply to the template (not page by page).
  • Add a safeguard: weight budget (KB) and CI check if possible.

Then: re-crawl 50–200 URLs, then monitor Search Console for 7–14 days (impressions/CTR/indexing).

Concrete example (illustrative)

Example (illustrative):

  • **Context**: blog article for B2B SaaS in Sfax
  • **Before**: Lighthouse: 48/100 (heavy JS, unoptimized images).
  • **After**: Lighthouse: 81/100 (lazy-load, compression, cache).
  • **Note**: Goal: stabilize INP.

Checklist to tick

  • [ ] Measure before/after
  • [ ] Improvement on template
  • [ ] No CWV regression
  • [ ] Cache and compression OK
FAQ

Frequently asked questions — G25

What is the most common error on “Service Worker”?

Trying to “optimize” by adding too many keywords, which degrades readability and creates repetitions.

What is the fastest tool to check at scale?

For this type of criterion, a crawl (e.g., Screaming Frog) + targeted verification in curl (headers) is generally the fastest combo.

How to prevent this from happening on 10K generated pages?

Freeze an auto-generation rule (title/structure/schema/URLs) + add automatic control (crawl or test) before production import.

Ready to go from theory to action?

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