The job of an SEO has certainly evolved over time due to Google cracking down on spam techniques, the rise of mobile, changes in the SERPs and so on. But what does an SEO really do these days, and how has this role changed over the years?A look into the past and presentOn-page optimization: When performing on-page optimization in the old days, SEOs would map two to five keywords per URL and optimize the page elements\u00a0(title, meta description, headings, body content and so on) for these keywords.But things have changed. Now, with advances in semantic search and machine learning, a page can rank for a lot of related keywords, not just the keywords for which you optimize the page. This is a better way of doing things, as having content that fulfills the needs of what users are looking for (rather than just being the best match for a given\u00a0keyword string) is a better experience.Modern-day SEOs\u00a0should have a solid understanding of not just content creation, but also content promotion. Whereas previously it was all about optimizing existing landing pages based on search volume and striking distance,\u00a0SEO today is a mixture of optimizing existing content and creating, optimizing and amplifying new content that meets end-users\u2019 needs to enforce your brand and capture social signals and links to rank higher in the SERPs.Devices: Back in the day, it was all about optimizing for desktops because that was the primary device used\u00a0to\u00a0surf the web.Today, mobile devices have quickly become the way that people consume content. While the desktop is still relevant, digital media consumption on mobile devices has skyrocketed in the past several years and will continue to grow. According to comScore, mobile now consists of 65 percent of digital media time. Additionally, in 2015, mobile officially surpassed desktop in terms of Google searches performed.SEOs must focus on optimizing the mobile experience, particularly apps, and making sure that mobile pages load within two seconds.Local: Google has changed its local results so many times during the past several years \u2014 from the10-pack to 7-packs, and now the 3-pack. In the old days of local SEO, it was easy to spam the listings by incorporating keywords into the business name, getting links from spammy directories, fudging the exact location of the business and so forth.Now, local is all about positive reviews and (thanks to the Pigeon update) some of the more traditional ranking signals\u00a0like relevance and page content.Social: Before the days of Facebook, Twitter and other social networks, online social\u00a0sharing largely took place via email and instant messaging \u2014 places that fell\u00a0largely outside of the scope of SEO campaigns.Today, social media is ubiquitous, and digital marketers who neglect this channel do so at their peril. Social media and SEO must work hand-in-hand to increase brand exposure, connect businesses with their audience and drive consumer engagement. The modern-day SEO must utilize social networks to promote content to\u00a0earn both shares and links for maximum exposure.Links:\u00a0Links have always been a significant factor in determining search engine rankings, but link building as a discipline has changed dramatically over the years.In the early days of SEO, it was all about link quantity \u2014 the more links to your site, the better. Anchor text was also more heavily weighted, meaning that links with keyword-rich anchor text could help a site rank better for those keywords. It was easy to get links from sites of questionable repute, and so many SEOs secured\u00a0links with keyword-rich anchor text from sites with high PageRank through link exchanges, direct requests or purchasing links.Today, it\u2019s not just about quantity, but about quality. Links from authoritative sites and sites relevant to your own are more heavily weighted, and links from spammy websites are discounted\u00a0(at best) or grounds for a ranking penalty (at worst). Additionally, search engines like to see a \u201cnatural\u201d link profile with a good mix of link types: follow and nofollow, keyword-rich anchor text and branded anchor text and so on.SEOs today must focus on\u00a0creating high-quality content and pursuing relevant links that are of value to users. They must also\u00a0monitor their\u00a0backlinks for any toxic links and remove low-quality links to maintain a healthy link portfolio.Technical SEO:\u00a0Technical SEO has not really changed much in the last few years, and the basic principles of technical audits still apply. However, SEOs must make sure their clients\u2019 sites are built in a mobile-friendly manner and load as quickly as possible. Technical SEO is now very much a requirement for web developers.Final thoughtsSEO has changed dramatically over the years, and we must adapt with it. An SEO\u2019s job has shifted from more traditional optimization to connecting the client\u2019s content with the end user over multiple devices and platforms.Instead of\u00a0search engine optimization specialists, maybe it\u2019s better to think of ourselves as content experience analysts: professionals\u00a0charged with optimizing a brand\u2019s\u00a0web properties\u00a0to attract consumers at all stages of the customer journey. If we can do this effectively, we will win in the SERPs.