The verdict in three sentences
In West Africa, a large share of traffic comes from 3G connections and modest phones, so speed is not a luxury but a commercial survival condition. Target LCP under 2.5 s and a page under 1 MB, converting images to AVIF/WebP. Every second saved turns into conversions, because 1 extra second of load ≈ -7 % conversion.
The Core Web Vitals targets
| Metric | "Good" 2026 target | Why |
|---|---|---|
| LCP (Largest Contentful Paint) | < 2.5 s | Speed of main content rendering |
| INP (Interaction to Next Paint) | < 200 ms | Responsiveness to clicks/taps |
| CLS (Cumulative Layout Shift) | < 0.1 | Visual stability (no "jumps") |
| Total page weight | < 1 MB | Critical on 3G |
| Mobile Lighthouse score | > 90 | Performance summary |
| Time To First Byte | < 800 ms | Server/CDN responsiveness |
How speed impacts the business
| Load time | Estimated effect on conversion | Effect on bounce |
|---|---|---|
| 1 s | Baseline | Baseline |
| 3 s | -14 to -20 % | +30 to 50 % |
| 5 s | -25 to -40 % | +90 % |
| Unoptimized image (heavy PNG) | Up to 2-3x useful weight | Abandon on 3G |
| AVIF/WebP migration | -60 to -80 % image weight | Strong bounce drop |
Images often make up 50 to 70 % of a page's weight: that is the first lever to pull.
The 3G optimization checklist
- Images in AVIF/WebP + exact dimensions + compression (-60 to -80 % weight).
- Lazy loading for off-screen images and iframes.
- CDN to bring files closer to the user (lower TTFB).
- Minify and defer non-critical JavaScript/CSS.
- Limit web fonts (1-2), with
font-display: swap. - Browser cache and Brotli/Gzip compression.
- Reserve media space to avoid CLS.
- Remove unnecessary third-party scripts (the biggest speed killer).
Need a professional website?
Kolonell builds websites that attract clients, optimized for the Sénégalese market. Free quote in 2 minutes.
Mini case study
Aissatou's e-commerce site shows an LCP of 5.2 s and a 3.4 MB page (PNG images, third-party scripts). After AVIF/WebP migration (page reduced to 0.9 MB), lazy loading and CDN, LCP drops to 2.2 s. On 4,000 visitors/month and a conversion rate rising from 1.2 % to 1.7 %, she gains 20 orders/month. At an average basket of 22,000 FCFA, that is +440,000 FCFA/month without spending a single franc more on advertising.
FAQ
Why target a weight under 1 MB? On 3G, a 3 MB page can take 8 to 12 s to load. Under 1 MB, you stay below the 2.5 s LCP threshold on most devices.
AVIF or WebP? AVIF compresses even better than WebP, but WebP is universally supported. Best practice: serve AVIF with a WebP/JPEG fallback depending on the browser.
Do Core Web Vitals affect SEO? Yes, they are part of Google's ranking signals and shape the mobile experience, which is decisive for ranking.
Are third-party scripts that harmful? Often yes. Chatbots, ad pixels and widgets add weight and block rendering. Remove the unnecessary and load the rest deferred.
How long to optimize an existing site? Usually 1 to 2 weeks for the major gains (images, lazy loading, CDN, scripts). Fine-tuning follows afterward.
Let's talk about your project. We audit your site and make it fast even on 3G, with Core Web Vitals in the green. WhatsApp +221 77 596 93 33.
Mohamed Bah
Fondateur, Kolonell
Passionate about digital and entrepreneurship in Africa, Mohamed has been helping Sénégalese businesses with their digital transformation since 2020. Founder of Kolonell, he believes every SME deserves a professional and accessible online présence.
