The essentials
- Definition: SEM (Search Engine Marketing) covers everything you do to be visible on search engines: organic search (SEO) and advertising (SEA).
- A nuance: in common usage, particularly in English-speaking countries, "SEM" sometimes means paid search alone. Check what a provider means by it.
- The logic: SEA captures demand immediately, SEO captures it lastingly; the data from each feeds the other.
- Typical split for a small business: 60 to 70% of the SEM budget on SEA in the first year, then a rebalancing towards SEO as the rankings arrive.
The term SEM (Search Engine Marketing) covers everything you do to be visible when someone searches: SEO (organic results) and SEA (paid ads). Summed up as SEM = SEO + SEA, it is a reminder that both levers aim at the same results page, the same people and the same intents — and that running them together works better than running them apart.
Beware the double meaning
In part of the literature, particularly in the United States, "SEM" means paid search only. When an agency offers you an "SEM engagement", ask whether it includes SEO. On this site, SEM keeps its broad sense: SEO + SEA.
SEO and SEA: what each is good at
| Criterion | SEO | SEA |
|---|---|---|
| Time to results | 3 to 12 months | Immediate |
| Cost | Time and skills, no cost per click | Pay per click, a continuous media budget |
| Durability | High: rankings persist | None: visibility stops with the budget |
| Control | Limited: Google decides | Total: keywords, messages, pages, times of day, areas |
| User trust | Higher on organic results | Lower, but you take the top position |
| Data | Search Console: queries, rankings | Google Ads: search terms, conversions per keyword, within days |
The detailed comparison is in SEA vs SEO: differences and how they complement each other.
How to combine them
- Test in SEA, invest in SEO. A Google Ads campaign reveals within two weeks which keywords convert; those keywords become the priority targets for your SEO content.
- Cover the queries where SEO isn't enough. On a query where you sit in position 5 to 10, an ad captures the traffic in the meantime; on a highly competitive query, SEA sometimes remains the only way in.
- Double your presence on brand queries. An ad on your own name costs little and stops a competitor taking that place, while occupying two results.
- Reduce SEA as SEO progresses. When a page reaches the top three organic positions, test lowering your bids on that keyword.
- Share your landing pages. A page built to convert paid traffic converts organic traffic too, and the conversion rate measured in SEA guides how you optimise your SEO pages.
Splitting the budget
| Situation | Indicative SEM split |
|---|---|
| Launch, a site with no history | 70% SEA, 30% SEO (technical foundations and first content) |
| Established site, middling rankings | 50 / 50 |
| Site ranking well on its key queries | 30% SEA (brand, uncovered queries, seasonality), 70% SEO |
| E-commerce | SEA (Shopping) dominant, SEO on categories and guides |
The trade-off also depends on your margin and your buying cycle: should you invest in Google Ads or SEO first goes through the cases.
The KPIs of an SEM strategy
- Share of voice on your strategic queries : present organically, in paid, or both.
- Traffic and conversions by channel (Organic Search and Paid Search in GA4), with SEA's cost per conversion and SEO's full cost.
- Overall acquisition cost on search, across all sources.
- Cannibalisation : when SEA captures clicks SEO was getting for free — measure it with pause tests.
SEM now extends to generative engines: visibility in ChatGPT, Perplexity and the AI Overviews falls under GEO, which rests on the same foundations as SEO.
How GreenRed helps
Rather than juggling several tools, GreenRed's overview brings these metrics together in a single dashboard, compares them over time and tells you which actions come first. You can try it free, with no card, from the Pricing.
Frequently asked questions
What is the difference between SEM, SEO and SEA?
SEO is organic search (unpaid results), SEA is search engine advertising (ads paid per click), and SEM is both together: all your visibility on search engines. In some usage, SEM means SEA alone; check which sense the person you're talking to means.
Should I do SEO or SEA?
Both, in proportions that depend on your situation. SEA brings results and data immediately; SEO builds visibility that lasts and costs less per visit. A small business starting out often invests in SEA first to learn, then rebalances towards SEO.
Does SEA improve SEO?
Not directly: Google states that ads don't influence organic ranking. Indirectly, yes: campaigns reveal which keywords convert, test messages and pages, and build recognition — and so brand searches, and sometimes links.
How do I measure an SEM strategy?
Through the traffic and conversions of the Organic Search and Paid Search channels in GA4, SEA's cost per conversion, SEO's full cost, and a query-by-query view combining Search Console (rankings, organic clicks) and Google Ads (cost, paid conversions). The goal is one overall acquisition cost on search, not two silos.