The verdict in three sentences
Core Web Vitals (LCP, INP, CLS) are both a Google ranking factor and a direct conversion lever: one extra second of load time costs roughly 7% of conversions. On the African web, where the median hovers around 3G/4G on entry-level Android devices, speed is won mainly on images, JavaScript and the CDN. The decision: fix incrementally (images, lazy-load, fonts) for the equivalent of 150,000-500,000 FCFA, or rebuild the architecture when the foundation is too heavy.
The thresholds to target in 2026
Google defines three zones (good / needs improvement / poor). Here are the official thresholds and what they imply on 3G.
| Metric | Good | Needs improvement | Poor | What it measures |
|---|---|---|---|---|
| LCP | < 2.5s | 2.5-4s | > 4s | Largest element load |
| INP | < 200 ms | 200-500 ms | > 500 ms | Responsiveness to input |
| CLS | < 0.1 | 0.1-0.25 | > 0.25 | Visual stability |
| TTFB | < 0.8s | 0.8-1.8s | > 1.8s | Server response time |
A site is judged "green" when 75% of real visits pass these thresholds. On 3G, LCP is almost always the sticking point, dragged up by unoptimised images.
Fixes vs impact: where to start
Not all optimisations are equal. Here is an effort/impact matrix (2026 order of magnitude) for prioritising.
| Fix | Effort | Typical LCP gain | Indicative cost |
|---|---|---|---|
| Compression + AVIF/WebP | Low | -1.2 to -2s | ~90-210 USD |
| Lazy-load images/iframes | Low | -0.4 to -0.8s | included in audit |
| font-display: swap | Low | -0.2 to -0.5s | included in audit |
| Reduce/defer JavaScript | Medium | -0.5 to -1.2s | ~180-440 USD |
| Edge CDN + cache | Medium | TTFB -1 to -1.4s | ~110-270 USD/setup |
| Architecture rebuild | High | LCP < 1.8s | see headless migration |
In 8 cases out of 10, image compression and lazy-load are enough to bring LCP under 2.5s. A rebuild is only justified on a genuinely overweight foundation.
Before / after on 3G
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Typical measurements (2026 estimate) on a brochure site before and after an optimisation audit, tested on an entry-level Android over 3G.
| Metric | Before | After audit |
|---|---|---|
| LCP | 4.6s | 2.2s |
| INP | 340 ms | 170 ms |
| CLS | 0.22 | 0.06 |
| Page weight | 3.4 MB | 1.2 MB |
| Mobile bounce rate | 61% | 44% |
| Conversion rate | 1.4% | 2.1% |
Mini case study
Amina sells spare parts online from Lagos; her site gets 20,000 visits/month with an LCP of 4.6s and a 1.4% conversion rate. She commissions a Core Web Vitals audit for the equivalent of 350,000 FCFA: AVIF compression, lazy-load, JS defer and an edge CDN. LCP drops to 2.2s and conversion rises to 2.1%, i.e. +0.7 point. On 20,000 visits and an average order of the equivalent of 15,000 FCFA, that represents 20,000 x 0.7% x 15,000 = 2,100,000 FCFA in additional monthly revenue. The audit pays for itself in the first week, before counting the gain in Google rankings.
FAQ
What Core Web Vitals thresholds should I hit? LCP under 2.5s, INP under 200ms and CLS under 0.1, for 75% of real visits. On 3G, LCP is almost always the blocker, usually because of heavy images.
Does speed really influence sales? Yes: roughly 7% of conversions lost per extra second of load time. Moving an LCP from 4.6s to 2.2s can lift the conversion rate from 1.4% to 2.1%, a considerable gain at equal traffic.
Do I need to rebuild everything to go fast? Rarely. In 8 cases out of 10, image compression (AVIF/WebP), lazy-load and JavaScript defer are enough to pass the thresholds. A rebuild is only justified on an overly heavy technical base.
How much does a performance audit cost? The equivalent of 150,000-500,000 FCFA depending on site size and fix depth. An audit includes real-user measurements, effort/impact prioritisation and implementation of the quick wins.
Why test specifically on 3G and entry-level Android? Because that is the reality of most African users. A site fast on fibre and iPhone can be unusable on 3G: only measurement on a modest mobile reflects the real experience.
Let's talk about your project. We audit your Core Web Vitals on 3G and deliver a prioritised fix 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.
