—Amino (Formerly Curren-C): This startup hopes to use blockchain technology to improve online ad billing and tracking. —msg.ai: Someone's going to figure out how to help marketers navigate chatbots and messaging and artificial intelligence using technology. It may be this company. —Omnivrt: This firm wants to bring ad tech like automation to virtual-reality ads. —Adswizz: There's potentially a big opportunity to bring programmatic advertising to digital audio, and this company is making a push. —Catch and Release: This company promises to help ad-agency creatives produce more visual ads at scale. —VidMob: This firm makes it easier to crank out social-video ads quickly by connecting marketers to a stable of producers. —IFTTT (If This Then That): This may be the company that helps marketers and media companies connect the dots between the growing number of digital in-home devices like Alexa and Google Home.Wait, isn't this list about independent, up-and-coming ad-tech companies? Isn't Amazon nearly a $500 billion company that has been public for decades? Yes. But inside the e-commerce giant is a stealth ad-tech startup. Amazon has quietly built software and tools that help advertisers buy programmatic ads and help publishers make more money from ads. It's one of the leaders in header bidding, an ad-tech technique that has revolutionized how digital ads are bought and sold by making the marketplace far more democratic. And don't forget Amazon's robust pool of consumer data. In a future where the average ad buyer and publisher will have the opportunity to bid on billions of ads at any given moment, he who has server capacity wins. And Amazon wins there big. The company actually called out how fast its ad team was growing during its most recent earnings call. You can argue whether Amazon qualifies as an ad tech upstart. But it's hard to argue about the company's effect on digital advertising.CEO: Scott Knoll Employees: 609 Estimated revenues: $122 million (trailing 12 months as of June 2017) Total funding to date: $54 million Comment: The more advertisers pay attention to where their ads are running and whether they can be seen, Integral becomes more important. Witness Oracle's acquisition of rival Moat for $850 million. Ad buyers and publishers praise their tech and leadership team.CEO: Michael Katz Employees: 87 Estimated revenues: $20 million in recurring revenue Total funding to date: $37 million Comment: This four-year-old firm helps marketers pull together data from all sorts of mobile and social services in a way they can actually use it. Clients include Starwood, NBC Universal, and Spotify. Luma Partners CEO Terrence Kawaja recently raved about the company on the Digiday podcast.CEO: Zvika Netter Employees: Over 200 Estimated revenues: $60 million Total funding to date: $65 million Comment: This video ad-tech company is at the forefront of delivering ads to TV apps, which now make up 22% of the ads it handles. That figure has jumped up 300% over last year. The firm also benefits from advertisers looking to make sure their ads are running in the right (read: safe) places on the web. Innovid says it deliver 90 million hours of video ads a month globally.CEO: Brian O'Kelley Employees: 1,000 Estimated revenues: Last year, we estimated it was in the realm of $250 million. Total funding to date: $281 million Comment: Could be valued at as much as $2 billion, according to The Wall Street Journal. The company is one of the biggest players in ad tech that could realistically challenge the likes of Google. It's backed by the ad holding giant WPP. Its long-rumored IPO is still TBD.CEO: Ragy Thomas Employees: 1,500 Estimated revenues: Sprinklr is estimated to have more than $200 million in annualized recurring software revenue, said a person familiar with the matter. Total funding to date: $228.5 million Comment: This company helps marketers manage their efforts across dozens of social-media channels. Clients include Microsoft and McDonald's. Sprinklr is valued at $1.8 billion.Of course Roku is not an ad-tech company. But its devices are in more homes than Apple and Google Chromecast. And did you know that the company has built its own suite of ad-tech designed to deliver, target, and measure ads served in TV apps? In other words, Roku could be quietly building the ad tech that will run through a huge network of web-connected TVs. Consider that Roku: has 14 million subscribers who streamed over 9 billion hours of content last year generated $400 million in revenue in 2016, including $100 million from its media and licensing segment, which includes advertising has roughly half of top 250 most-watched channels on Roku are ad supported, and the ad-supported segment is the fastest-growing on the Roku platform delivers about a third of all OTT ad impressions (claimed) CEO: Aaron Bell Employees: 500 Estimated revenues: $300 million run rate this year Total funding to date: $89 million Comment: This company is seen as something of a next-generation Criteo for mobile devices, specializing in helping advertisers retarget people who have shown interests in buying particular products. AdRoll says it has over 35,000 active customers, and as Business Insider reported, Snapchat has kicked the tires on this San Francisco firm.CEO: Bill Magnuson Employees: 175 Estimated revenues: annual recurring revenue in the range of $30 million to $50 million, said a person familiar with the matter Total funding to date: $93.6 million Comments: AppBoy aspires to be something of a mobile answer to the marketing clouds offered by the likes of Adobe and Salesforce. The company works with marketers like Nascar and Domino's to help manage advertising across channels. The startup raised $20 million last year right in the middle of an ad-tech funding drought, as AdExchanger reported, and another $50 million in a series D round this month. Mobile marketing remains an area of big upside. Witness the eye-opening $1.4 billion deal for AppLovin last year. It's now valued at more than $400 millionCEO: Joe Zawadzki Employees: 700 Estimated revenues: $265 million Total funding to date: Recently secured a $175 million credit facility. Raised $175 million in 2014. Comment: Mediamath has been around for a while without an exit, and its recent debt-driven funding round perhaps raised some eyebrows. But it's also one of the largest revenue-generating ad-tech companies out there, and it still has connections to major marketers and its technology is respected.CEO: Mike Henry Employees: Over 75 Estimated revenues: $25 million net Total funding to date: $18 million Comment: When YouTube was hit with a string of bad ad placements, ad-buying giant GroupM tapped OpenSlate to help it find brand safe videos to advertise next to. OpenSlate is a go-to for brands trying to navigate the confusing and crowded YouTube creator space.CEO: Ashwin Navin Employees: 195 by the end of 2017 Estimated revenues: $51.2 million in 2016 Total funding to date: $38.16 Comment: Samba TV just reeled in $30 million in new funding. The company, endorsed by Mark Cuban, is positioned to become the arbiter of truth as TV viewership shifts rapidly. It pulls together viewership data from smart TVs, TV apps, and cable boxes, and it tries to make sense of the way people watch TV and encounter ads in 2017. Investors include the ad holding companies Interpublic Group and MDC Ventures as well as Time Warner and A+E Networks.CEO: Jarrod Dicker is the company's vice president of commercial product and innovation and leads the company's in-house ad-tech initiative. Employees: 10 Estimated revenues: The media company has seen double-digit advertising-revenue growth, including a 113% increase in programmatic revenue and 129% in branded content. Digital advertising is now a nine-figure business at the company, according to people familiar with the matter. Comment: The Washington Post is a media company that is quietly incubating Red, an ad-tech division that licenses tools and ad products to other publishers. The company is often praised for its progressive digital approach. The Red team says that since 2016 it has produced 10 products, including the Brand Insights Dashboard, that have been purchased by more than 150 clients.CEO: Ran Sarig Employees: 250 Estimated revenues: $30 million to $40 million in net revenue, according to people familiar with the matter Total funding to date: $50 million Comment: One of the fastest-growing companies in the space as tracked by Pivotal Research. Datorama promises marketers it can help unify all their data across platforms, help the track actual consumers, and make better decisions on where to spend their media budgets. The company, which raised $32 million in 2016, is investing in machine learning and artificial intelligence.CEO: Ryan Urban Employees: 250 Estimated revenues: $60 million Total funding to date: $38.85 Comment: This company bills itself as a cloud-based behavioral-data company. Essentially it promises to provide companies — ranging from Sears to Kate Spade to Gannett — with a richer understanding of their web visitors. BounceX claims to have data on 200 million users that can be used to track people as move from device to device, an increasingly crucial need in digital advertising.CEO: Sean Muller Employees: 115 Estimated revenues: Roughly $30 million, according to people familiar with the matter. Total funding to date: $58 million Comment: Think of iSpot as a Moat for TV. The company pulls data from Smart TVs and has access to unique information on what people watch, what ads are delivered, and whether people stay tuned. They work with many big TV networks and advertisers. The company's valuation was at $112 million as of two years ago.CEO: Mihael Mikek Employees: 165 Estimated revenues: $50 million Total funding to date: $25 million Comment: This startup is one of the rare ad-tech firms succeeding at making the production of digital ad creative more automated and scientific. Celtra has recently received investment from the marketing giant Unilever and the ad agency holding company WPP, reported AdExchanger.CEO: Jonathan Mendez Employees: 100 Estimated revenues: $50 million Total funding to date: $100 million Comment: The company promises it can help brands find prospects when they are in the right frame of mind to receive pitches using data on consumer intent. Yieldbot says it can help these marketers connect mobile ads to store visits and even purchases.CEO: Ari Paparo Employees: 30 Estimated revenues: $10 million Total funding to date: $35 million Comment: Think of Beeswax as offering white-label ad tech. You don't need to build or buy your own real-time ad-buying technology platform. You can use Beeswax's software and tools for a fraction of the price. As owning a second- or third-tier ad-tech company becomes less viable, this company is in a good spot.