The verdict in three sentences
On a West African 3G network, your goal is a first load under 1 MB and an LCP under 2.5s. The three levers that pay off most are WebP/AVIF image compression, JavaScript reduction and SSG/SSR rendering. Applied well, they turn a 4 MB, 6s site into an 800 KB, 1.5s site, with a direct impact on conversions and mobile SEO.
Target metrics on 3G
| Metric | 3G target | Bad signal | Impact |
|---|---|---|---|
| LCP (main paint) | < 2.5s | > 4s | SEO + bounce |
| TTI (interactivity) | < 5s | > 8s | User frustration |
| First-load weight | < 1 MB | > 2.5 MB | Data cost + slowness |
| HTTP requests | < 30 | > 60 | Cumulative latency |
| CLS (visual stability) | < 0.1 | > 0.25 | Missed clicks |
| Executed JS weight | < 200 KB | > 600 KB | Degraded TTI |
On real 3G (~1.6 Mbps, 300 ms latency), every megabyte adds about 5 seconds of transfer. Hence the absolute priority on weight.
Gain per optimization technique
| Technique | Effort | Typical LCP gain | Weight reduction |
|---|---|---|---|
| WebP/AVIF images | Low | -1 to -2s | -40 to -70% images |
| Lazy loading images/iframes | Low | -0.5 to -1.5s | -30% on load |
| CDN near visitors | Medium | -0.5 to -1s | latency -100 ms |
| SSG / SSR (pre-render) | Medium | -1 to -2.5s | -50% blocking JS |
| System fonts (no webfont) | Low | -0.3 to -0.8s | -50 to -200 KB |
| Code splitting | Medium | -0.5 to -1.5s | -30 to -60% JS |
| Aggressive HTTP caching | Low | near-instant repeat visits | -90% on return |
The winning sequence: images first (the biggest weight item), then JavaScript, then network (CDN, cache). Aim for a performance budget written down and enforced on every deploy.
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Mini case study
Ibrahim runs a restaurant site in Abidjan. Homepage: 3.9 MB, LCP 6.2s on 3G, 70% mobile bounce. We convert 14 JPEGs to AVIF (-1.9 MB), enable lazy loading (-0.7s), swap a webfont for a system font (-0.5s) and switch to SSG (-1.6s). Result: 820 KB, LCP 1.9s. Average time on site doubles and online reservations rise about 25%, without a single franc of extra media spend.
FAQ
Why aim for under 1 MB exactly? Because on real 3G at ~1.6 Mbps, 1 MB transfers in about 5s. Staying under that threshold keeps LCP below 2.5s, where Google rewards mobile SEO.
WebP or AVIF in 2026? AVIF compresses 20 to 30% more than WebP at equal quality, but WebP remains an excellent universal fallback. Best practice: serve AVIF with an automatic WebP fallback.
Does lazy loading hurt SEO? No, if done right: the main (LCP) image must stay eagerly loaded, and only below-the-fold images are deferred. Misconfigured, it can actually degrade LCP.
Is a CDN useful if my audience is only in Dakar? Yes: a CDN with a point of presence in Africa or Europe cuts latency and caches your static files, saving 100 to 300 ms per request on repeat visits.
Let's talk about your project. We audit your site and hand you a costed 3G optimization plan. 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.
