2013 has been quite the year for online advertisers, especially those who rely heavily on Google.

During the first half of this year, Google transitioned its AdWords customers to its Enhanced Campaigns. The new campaign management interface met with a mixed reaction from advertisers, though Google provided a nearly endless stream of educational material ahead of the upgrade deadline.

How have Google’s 2013 ad changes affected you? Tell us in the comments.

While Google’s traditional search advertising offerings underwent significant changes, the company’s focus further shifted toward mobile this year. Mobile ads are nothing new for Google, which has been trying out various mobile ad offerings for years. 2013, though, marked a shift in ad priority not just from Google, but from other mobile platforms as well.

Google itself is steadily growing Android into the Windows of the mobile world, with the mobile OS appearing now on a vast majority of the smartphones shipped throughout the world. Though the freedom of Android has enabled the software to proliferate, it could also mean that companies use the OS to support their own marketing. Amazon’s Kindle Fire devices are a perfect example of this, with Amazon going so far as to sell ad space on users’ lock screens. For the most part, though, Google Play and Google Search are front-and-center in the Android experience.

Apple, of course, is still a leading mobile advertiser that takes a major chunk of global ad revenues each quarter. Confident in its mobile success, Apple is rumored to be moving into Google’s search territory as more and more of the world’s searches are performed on Apple’s mobile devices. Signs point to the company soon diving into search, possibly with its own mobile search platform.

Samsung also forged ahead with its mobile ad strategy, though its time may have to wait until it can challenge Android’s mobile supremacy with its Tizen OS, which reportedly won’t happen any time soon.

With the mobile ad landscape growing and taking shape, another of Google’s ad priorities is the world of social networking.

YouTube is still a prominent ad platform for Google, and the site featured more and a larger variety of ads than ever in 2013. Traditional advertisers have certainly come around on YouTube as a legitimate platform for video advertising as Google has taken great strides to accommodate traditional content holders with its shoot-first policy on copyright offenses. YouTube viewers and advertisers can look forward to even more ads in 2014, along with expanded video content offerings.

Though Google has a habit of giving up on even well-loved projects that just aren’t popular (see Reader, which died an untimely death this summer), the company still seems to be leaning hard on Google+ for its social network strategy. In fact, Google seems determined to push Google+ despite outright hatred for the platform from some segments of the internet.

Google+ was a large part of the backlash against the YouTube comments change that rolled out in early November. YouTube users spoke out loudly against the changes, which include integration of Google+ comments, accounts, and circles, as well as a comment surfacing system that seems to bury comments with plenty of thumb-ups.

It is still unclear how Google hopes to use Google+ in its overall advertising plans, though the company might see the platform as necessary to compete with top social networking platforms such as Facebook and Twitter. Whether Google+ is up to the task or not, it’s clear now that social media is an El Dorado for advertisers and Google will continue to grab for its chunk of the market. Twitter ads have become more targeted than ever this year, and Facebook has begun competing directly with YouTube for advertisers through its new autoplay video ads.

Will Google ever be able to break into social media in a big way? Leave your thoughts in the comments below.

So that’s where online advertising stands for Google at the close of 2013. The trifecta of search, mobile, and social is a lucrative one for advertisers, and Google in particular. With search practically locked-up and the mobile and social realms quickly becoming saturated, however, strong future ad growth will need to rely on something new.

Sure, Google Glass might usher in a new era of Google ads projected directly into eyeballs, Google’s vehicle technology could mean driverless taxi cabs covered in Google ads (inside and out), and Boston Dynamics-created robots could deliver ad messaging up the sides of buildings – but all of these things are still years (if not decades) away. In the short term, there is still one screen beyond the PC, smartphone, and tablet that Google has yet to conquer in the home.

A new report out this week suggests that Google may soon shift its TV strategy more toward its Android platform. Though Google TV can arguably be called a flop, the company’s recently-released Chromecast appears to be a genuine hit. The inexpensive USB/HDMI dongle seems to have finally connected the TV and second-screen devices in a way that resonates with customers.

Google’s quick shutdown of a local video streaming app for the Chromecast shows that Google has big plans for the device, and those plans include keeping Chromecast content securely gated. This could suggest that Chromecast is being groomed as a platform for both banner and video ads – a merger of web and mobile advertising that would seem to flow straight from Google’s current initiatives.

With more content available to stream through services such as Netflix and Hulu, the way that consumers watch television is changing rapidly. Though manufacturers have tried to get ahead of the market in the past few years with set-top boxes, video game consoles, and smart TVs, it could be Google’s small Chromecast dongle that brings streaming video (and ads) to consumer living rooms. That would certainly represent a huge opportunity for both Google and advertisers – and it could begin happening as early as next year.

How do you think Google will change online advertising next year? Let us know in the comments below.