Search engine marketing (SEM) is promoting a business on search engines, most often by paying for ads that appear above or beside the search results. Advertisers bid on the keywords people search for, and pay when someone clicks. This guide explains how SEM works, how it differs from SEO, what it costs and how to start.
What is search engine marketing?
SEM means paid search advertising on engines such as Google and Bing. When someone searches “emergency plumber Leeds”, an auction decides which ads appear and in what order, based on the advertiser’s bids and the quality of the ads and landing pages. The ad is shown at that moment, to someone who is already looking.
The term is sometimes used more broadly to include SEO as well, but most marketers use SEM for paid search. See search engine marketing and paid search in the glossary.
How paid search works
- Choose keywords that match what your customers search for.
- Write ads with headlines and descriptions that match those searches.
- Set a budget and bids, or let automated bidding aim for a goal such as conversions.
- Send clicks to a relevant landing page.
- The auction runs each time someone searches. Ad Rank depends on your bid and on quality signals such as expected click-through rate, ad relevance and landing page experience.
- You pay when someone clicks (pay per click), and you measure what happens next.
Google summarises the quality signals in a diagnostic score for each keyword. See Quality Score.
SEM vs SEO
| SEM (paid search) | SEO (organic) | |
|---|---|---|
| Speed | Results as soon as ads are approved | Builds over months |
| Cost | You pay per click | No click fee, but time and content costs |
| Control | High: you choose the message and the page | Lower: the search engine decides |
| Duration | Stops when the budget stops | Can last a long time |
| Best for | Tests, offers, high-intent searches | Lasting visibility and trust |
Most businesses use both: paid search for fast results and testing, SEO for lasting visibility. Data from search ads, such as which phrases convert, can also guide your SEO content.
What does SEM cost?
You set the budget. The price per click comes from the auction and varies by keyword, industry and competition: clicks for local services can cost little, while clicks for legal or insurance terms cost much more. Start with a small test budget, check cost per click and cost per acquisition and compare with the profit per customer.
A setup checklist
- Install conversion tracking for calls, forms and purchases before you spend anything.
- Group keywords by theme, and write ads for each group.
- Add negative keywords to avoid irrelevant clicks, such as “jobs”, “free” or “course” when they do not fit.
- Add assets such as sitelinks, callouts and call buttons. See ad extensions.
- Use a landing page that matches each ad. See landing pages.
- Review the search terms report each week and adjust.
For managed campaigns, see our guide to PPC campaign management services and the Google Ads service.
Common SEM mistakes
- Sending all ads to the home page.
- No conversion tracking, so you judge by clicks only.
- Broad keywords with no negative keywords.
- Letting automatic features spend money without checking where ads appear.
- Changing everything at once, which makes it impossible to learn what worked.
Conclusion
SEM gives fast, measurable access to people who are already searching. Start small, track the right conversions, send clicks to a matching page and review results weekly. Use it alongside SEO, and let each channel inform the other.
Terms in this guide
