The verdict in three sentences
In Senegal, a significant share of mobile traffic still runs over 3G, where every byte counts: on a slow connection, a single 1.8 MB image can add 3 to 4 seconds of load time. The most profitable fix is not switching hosts but optimizing images (WebP/AVIF, responsive sizing, lazy loading), which often cuts a page's weight by five to ten times. 2026 target: total weight under 1 MB and LCP under 2.5 s, the threshold that improves both visitor comfort and Google ranking.
Before / after: what an optimized image gains
Images account for an average of 50 to 70 % of a showcase page's weight. The table shows the effect of a simple optimization chain on a restaurant homepage loaded on slow 3G (2026 order of magnitude).
| Element | Before | After | Reduction |
|---|---|---|---|
| Hero JPEG image | 1,800 KB | 180 KB (WebP) | -90 % |
| 8-photo gallery | 6,400 KB | 720 KB (AVIF) | -89 % |
| Total page weight | 9.2 MB | 940 KB | -90 % |
| LCP (slow 3G) | 5.4 s | 2.1 s | -61 % |
| Time to interactive | 8.1 s | 3.0 s | -63 % |
| Data used per visit | 9.2 MB | 0.9 MB | -90 % |
The performance budget, line by line
A "performance budget" sets a weight ceiling per resource type so you never slide back into slowness. Here is a realistic target for a lightweight showcase or e-commerce site aiming at 3G.
| Resource | Target budget | Main lever |
|---|---|---|
| Images (total) | < 500 KB | WebP/AVIF + responsive |
| JavaScript | < 200 KB | Code-splitting, tree-shaking |
| CSS | < 60 KB | Purge unused classes |
| Fonts | < 100 KB | 2 weights max, woff2, swap |
| HTML | < 30 KB | Static rendering |
| Total weight | < 1 MB | Sum of budgets |
| LCP target | < 2.5 s | Preloaded hero image |
Mini case study
Modou runs an online clothing shop in Dakar. His site loaded in 5.8 s on mobile with a 61 % bounce rate. After converting 40 images to WebP, lazy-loading the gallery and removing two useless scripts, weight drops from 8.4 MB to 860 KB and LCP falls to 2.2 s. Bounce rate drops to 42 %, a 19-point gain. On 3,000 monthly visitors and a conversion rate rising from 1.2 % to 1.9 %, he records 21 more orders per month; at an average ticket of 18,000 FCFA, that is 378,000 FCFA of additional monthly sales.
FAQ
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WebP or AVIF — which to choose in 2026?
AVIF compresses better (often 20 to 30 % smaller than WebP at equal quality) and is now widely supported. Best practice: serve AVIF first with a WebP fallback, and keep JPEG as a last resort for very old browsers.
Is lazy loading enough on its own?
No. Lazy loading avoids downloading off-screen images, but the "hero" image visible on load stays heavy if it is not compressed. You must combine compression, a modern format and lazy loading to keep the budget under 1 MB.
Why target LCP under 2.5 s specifically?
It is Google's official "good" threshold for Core Web Vitals. Below it, the page is deemed fast and gets a slight ranking edge; above 4 s, mobile bounce rate rises sharply, especially on 3G.
Would a better host solve the problem?
Rarely on its own. Hosting affects server time (TTFB), but on 3G the bottleneck is the amount of data to transfer. Optimizing images yields a far greater gain than the cost of premium hosting.
How do I measure my real 3G speed?
Use PageSpeed Insights (which simulates mobile) and the network tab of developer tools set to "Slow 3G." Focus on LCP and total transferred weight, not just the overall score.
Let's talk about your project. We audit your site's speed and make it smooth even on 3G. 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.
