SEM vs SEO Explained: Differences, Similarities and How To Choose Your Strategy

SEM vs SEO Explained: Differences, Similarities and How To Choose Your Strategy
Article by Bisera Stankovska
Last Updated: June 27, 2022

Google processes over 40,000 search queries every second. This giant engine has been perfecting its content filtering and ranking algorithms for decades to serve users with more relevant information when they need it.

For that reason, simply owning a website isn’t enough to reach your potential customers. You not only have to optimize your website for Google’s crawlers, but you also need to rank on the first of the search engine results pages (SERP) to win this organic traffic.

There are two ways to do that: using search engine marketing (SEM) and search engine optimization (SEO).

In the next sections, we’ll explain what SEM and SEO are, what they have in common, and what are the differences between them. At last, we’ll discuss SEM vs SEO and determine which one you should invest in.

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What Is SEM?

Search engine marketing or SEM is the practice of using paid ads to feature your web page at the top of SERPs. SEM campaigns are based on a keyword bidding system. Using Google Adwords, marketers place bids for targeted keywords. The highest bids and the best optimized SEM campaigns secure the top positions for the targetted keyword.

Now, notice we said "the highest bid and the best optimized" campaign. Simply buying an ad won’t do you any good. You still need to invest time and effort into finding the right keywords, optimizing your landing page for relevance by ensuring your content matches the users’ search intent, and optimizing the ad itself following Google’s guidelines and best practices.

These are the elements that go into SEM campaign building:

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Keyword Research

Keywords are the terms users type in the search engine to find the content they’re looking for. Some keywords are of informational character such as definitions and guides. These are typically used for blogs that work best as top-of-the-funnel content, so not the ideal choice for ads.

The best keywords to choose are those with transactional or commercial intent.

To find these, think about what your prospects might be typing in the search engine when looking for products or services in your domain.

Think of keywords that include "buy," "discount," "deal," "coupon," and "free shipping" – to name a few.

We’ll talk more about the keywords later on in this SEM vs SEO breakdown.

Ad Copy

Once you have the relevant keywords, it’s time to create ad copy. Your ad copy should be valuable and engaging enough for target users to click on it.

The ad title should correspond to the user’s search intent, ideally specifying your offering or unique value proposition.

The display URL should be simple and in line with the title. Keep your display URL simple and include your keyword.

The meta description provides most real estate for copy, so use it to specify your offering and unique value proposition(s).

Note that, to optimize performance, Google will allow you to define multiple versions of your ad titles and descriptions.

Ad Auction

Once your campaign is ready, it’s time to bid on the target keyword(s). Let’s see what that means.

Each time someone enters a search query into Google, the ad auction process starts. Advertisers that want to take part in it will identify keywords they want to bid on and state how much they are willing to spend per click.

But, not every ad that bids will appear among the search results. There are two ways Google uses to determine whether your ad will show up on the SERP: maximum bid and Quality Score.

The maximum bid is the approximate amount you’d pay for a click. If this amount is greater than your competitors, your chances of ranking at the top are greater as well.

The Quality Score is a metric that determines the quality of your ad, including how well it matches the search intent for the keyword it is targetting. Ads with better scores enjoy an advantage over other bidders and their cost per click (CPC) even goes down! For that reason, the most important thing when it comes to ads is their quality.

Now, let’s move on to the "SEO" part of the SEM vs SEO overview.

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What is SEO?

SEO is the practice of writing or adjusting your website content guided by target keywords to make it more accessible to search engine crawlers and increase the chances of ranking on SERPs through non-paid (organic) techniques.

So, there’s a big difference between SEM vs SEO: SEM involves paid ads, while SEO relies on content and is – theoretically – ranked purely on „merit“.

A big part of SEO is knowing your target audience and the search intent behind the query. In other words: what is it they want to find when googling this keyword? What type of content? What information? And even what follow-up questions they might have.

While content is the key pillar of optimization, SEO is – in fact – composed of three components:

  • On-site SEO
  • Off-site SEO
  • Technical SEO

If you’re not familiar with any of this, don’t worry. Here’s an explanation:

On-site SEO

On-site SEO refers to optimizing the content and HTML source code of a page or entire website.

At the core of on-site optimization is high-quality content. No matter how easy a keyword is to rank for or how many links point to your page, if users are not spending time reading your content and if they are returning to the search engine to see other results, you won’t rank for long.

That’s not to say that keywords don’t matter – they absolutely do! But the way SEM vs SEO optimization for keywords is a little different.

Unlike SEM, SEO needs time, so experts try to be smart with how they choose their keywords. For example, ranking high for one-word keywords such as „shoes“ or „bikes“ is difficult because there are a lot of companies that sell them online. Many of them, such as Jimmy Choo or Louboutin, are extremely well-known so they tend to have an advantage over competitors. You simply won’t stand a chance against them, at least not in the beginning.

For that reason, it’s best to find some long-tail keywords that are typically more specific, get less traffic, and, therefore, less competition. Improving your search engine positioning is much easier with long-tail keywords. Of course, you’ll still need to make sure they are relevant to your business and that users are interested in those topics.

When optimizing in SEO, you want to make sure to include these keywords in the title, headings, and meta description, as well as throughout the rest of the content where they fit naturally.

Aside from keywords, another technique SEO companies use is internal linking. This means linking to related and relevant pages on your website so crawlers won’t have a hard time finding new content. Users also enjoy finding more insights, so these links are good for user experience too.

Off-site SEO

When discussing SEM vs SEO, it’s impossible to skip off-site SEO. While search engine marketing activities are done solely on your website (and the ad manager!), off-site SEO – as the name suggests – happens outside your website.

Off-site SEO is the activities aimed at increasing the number of websites that link to your content.

The goal is to improve the search engine’s perception of your site's popularity, relevance, trustworthiness, and authority through links.

The best off-site SEO is when someone adds the link to your website without any intervention on your behalf: for instance, a blogger mentions your products or your content simply because they love it.

It can also be deliberate, through link-building activities with influencers or guest posting.

Technical SEO

Technical SEO refers to optimizing your website’s code and other technical elements to make content discoverable, accessible, and easily readable to search engines.


How Are SEM and SEO Similar?

Before we get into the key SEM vs SEO differences, let’s look at some of their similarities.

They Share the Same Goal.

The first thing SEM and SEO have in common is their goal: they both aim to grow a business and increase website traffic.

Now, they do have different approaches to this goal. Search engine marketing relies on paid ads to convert users into customers, while search engine optimization uses non-paid techniques for that purpose. Still, they’re two sides of the same coin.

Both Rely on Keywords.

As we’ve already mentioned, both SEM and SEO use keywords to reach the top of the SERP.

The main premise of both SEM and SEO is to meet users in search by providing solutions and answers to their queries and funneling them into your website. The Quality of The Copy Comes First.

As we’ve already established, you can never make up for bad content – no amount of optimization best practices or links can do the trick.


Because Google „observes“ searchers’ behavior on your webpage. If they are leaving after a few seconds, and if they are returning to the search engine to explore other results, this is a clear hint to Google that your content has failed to meet to searchers’ expectations.

Every blog you write and every landing page you create must bring value to the users.

4 Key SEM And SEO Differences

Both focus on driving qualified traffic to your website via search engines. Now let’s see how SEM vs. SEO differs:

1. SEO is (Theoretically) More Affordable.

As you know by now, SEM uses pay-per-click ads to place your content at the top of the SERP for targeted keywords. Each time a user clicks on your advertised link, you are charged a fee.

So, SEM has very clear costs involved. There is a way to lower them. We’ve already seen that high-quality ads rank better for lower investments. However, optimizing your ads and the linked page(s) requires time which can represent additional costs.

SEO, on the other hand, is free – at least nominally.

Optimizing your content using SEO techniques is indeed free. Google doesn’t charge for SEO. But, you do need to create high-quality content, optimize it, run technical audits and apply fixes, build links, and that’s the catch – these things don’t come for free.

First, to find viable keywords, you need a keyword research tool. While most of these tools have a free version, premium versions will allow you to see more keywords, assess their difficulty, know the monthly search volumes in target geographies, and so on. Ahrefs Keyword Research Tool, for instance, starts at $99 and goes up to $999 a month, depending on the included features.

Also, high-quality content, technical optimization, and link building don’t come for free. You’ll need an experienced content writer, an SEO specialist, and possibly outreaches that will ensure the content is fully optimized.

As you can see, SEO isn’t actually for free, it just has no fixed costs.

2. Results Are Faster with SEM.

When talking about SEM vs SEO in terms of timeframes, SEM definitely has the upper hand here, as SEO takes time to work.

A newly created website may take up to 4 weeks to be crawled and indexed by Google. But, that’s not the end. Research by Ahrefs showed that it takes two years on average to rank in the top 10 results on the SERP. From building credibility with Google to creating content and fixing SEO issues if and when they arise, seeing results from SEO can take some time.

SEM is almost immediate. From the moment an ad is approved to the moment it starts showing up in search and driving traffic to your website, you’re looking at days if not hours.

3. SEO Delivers Long-Term Value.

While SEM may work faster than SEO, there’s something to be said about longevity in the SEM vs SEO debate.

Sure, SEO does take some time, but once it does, you’re likely to stay in your position over time without significant investments in maintenance.

SEM, on the other hand, works only while you’re paying for it. The moment you stop doing it, you’re back to where you were traffic-wise. Also, it's not a quick solution for how to fix your SEO.

Of course, this doesn’t mean you can’t do both SEM and SEO at the same time. You can start with an SEM campaign and work on optimizing the rest of your content for SEO in parallel.

4. SEM Has a Lower Click-Through Rate.

The click-through rate shows the percentage of people that click on your link from the SERP. This metric is very important for both SEO and SEM. This is where SEO dominates the SEM vs SEO debate.

Apparently, as many as 70% of online marketers state that SEO is better than SEM when it comes to generating sales. This may have to do something with the user’s lack of trust when it comes to paid ads.

Should You Invest In SEM or SEO?

As you can see, there are several differences you should keep in mind when talking about SEM vs SEO. Deciding which one you’ll use and if you’ll combine them depends on several factors.

Types of Keywords

We’ve already mentioned that SEO is best for long-tail keywords, while SEM is most effective with more competitive, typically short-tail, keywords. But, there’s something else you should know when it comes to keyword types.

Informational keywords, such as ’how-to’ blogs, perform better with SEO than SEM. This is because you don’t want to waste too much money on people that are here to learn, not buy. Most of them won’t purchase your products, but they will help you build and improve brand awareness.


If you’re in a hurry, you’re better off using SEM. It takes time to create a sufficient amount of content and optimize it in a way that brings results organically. SEM works as soon as you enter the ad auction.


If you’re a small business owner or a startup, you probably have a limited budget for advertising. As Google ads can be pretty expensive to drive results, especially if you don’t have the best copy, you’ll probably want to focus on SEO understanding that it is a long game.


SEM requires knowledge of keyword research, copywriting, and platform-specific best practices.

But, so does SEO. Understanding the basics of SEO is key to successful SEM as it requires proficiency in keyword research and landing page optimization.

This is why it is typically advisable to start with SEO. You won’t spend (much) money in the learning process, but you will acquire the foundational knowledge for both SEM and SEO.

Takeaways on SEM vs SEO

Hopefully, this SEM vs SEO comparison helped you understand these two practices a bit better.

Both SEM and SEO can help you increase your website traffic and acquire new customers via search engines.

Besides their many similarities like their shared channel – search engines – and reliance on keywords, the main difference between SEM and SEO is that SEM aims to acquire paid placement while SEO aims to acquire organic placements for target keywords on SERPs.

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