The tech sector has propelled lion's share of the market's overall gains across the last decade, with highly scalable business models fueled by the increasing integration of technology into all facets of everyday life.

The titans of the sector have generally continued to post strong performances in 2018, with the Dow Jones U.S. Large Cap Technology Index up roughly 15% so far. But while the mega caps get the headlines, it's the small-cap tech companies that have posted the most explosive gains.

Read on for a look at why the valuations of TechTarget Inc. (NASDAQ:TTGT), eGain Communications Corp. (NASDAQ:EGAN), ShotSpotter Inc. (NASDAQ:SSTI), Inteslat S.A. (NYSE:I), and Turtle Beach (NASDAQ:HEAR) have skyrocketed in 2018 -- and see where each ranks on the list of the tech industry's biggest gainers year to date.

Five arrows pointing straight up.

Image source: Getty Images.

5. TechTarget: Up 142%

TechTarget stock soared in 2018 thanks to strong customer growth, as well as progress on transitioning its sales stream to long-term, recurring revenue sources. The company provides data and analytics services to help tech companies better understand purchase intent in the enterprise market. 

TTGT Chart

TTGT data by YCharts

TechTarget has been successfully building its client base and growing sales of its key services. Revenue for the company's Priority Engine, a software service for sales and marketing teams that identifies enterprise technology customers and suggests marketing approaches based on what's likely to be effective, more than doubled in the quarter. This strong performance helped drive revenue derived from long-term contracts to roughly 34% of sales -- up from 18% in the prior-year quarter. The company also increased its total customer count from 450 in the first quarter of 2017 to 600 in Q1 2018.

4. eGain: Up 180%

eGain has posted huge gains as it's made rapid progress on its transition from a one-time sales model to a software-as-a-service (SaaS) model. The company provides customer-service chat software, virtual assistants, analytics, and other services for enterprise applications, and its transition to a recurring-revenue model looks to make the business significantly more dependable and profitable. 

EGAN Chart

EGAN data by YCharts

eGain is now moving through its first year as a SaaS-focused business. Revenue from its services business climbed 74% year over year in the company's most recent quarter to reach $8.9 million -- or roughly 54% of total revenue in the period. Total recurring revenue climbed 30% to account for 84% of overall sales.  The company has a market cap of roughly $400 million, up roughly 700% over the last year, and trades at 134 times this year's expected earnings and 5.9 times expected sales. 

3. ShotSpotter: Up 205%

ShotSpotter manufactures gunshot-detection technology and provides related support services to law enforcement. The company's basic hook is that its specialized microphones and infrared-scanning tech can tell police with some precision what area shots were fired in -- enabling faster response times, and improving civilian and officer safety.

The company's share price skyrocketed in 2018 in response to a series of high-profile mass shootings, new cities signing on to use or expand their use of the company's products, and encouraging earnings results. It now has a market cap of roughly $460 million. ShotSpotter's technology is now used in more than 90 cities in the U.S. Most recently, Toronto's police board approved its use, though the city still has to allocate funds for it.

SSTI Chart

SSTI data by YCharts

ShotSpotter is valued at roughly 14 times this year's expected sales -- a highly growth-dependent valuation, but one that leaves room for capital appreciation if the company can defend its niche against resource-rich competitors like Ratheon. It will report its Q2 earnings and host a conference call on Aug. 2.

2. Intelsat S.A.: Up 451%

Intelsat stock skyrocketed following indications that the Federal Communications Commission (FCC) was looking favorably at the company's proposal to open up a wider range of the C-band wireless spectrum for commercial use. The satellite-communications company already has most of the key infrastructure it would need to take advantage of that change, and it could play a crucial role in one of the most significant technology shifts on the horizon.

I Chart

I data by YCharts

Intelsat has proposed opening up the 3,700 megahertz to 4,200 megahertz frequency range of the C-band spectrum for use by terrestrial mobile networks in order to support the expansion of 5G networks.

5G network technology will be necessary to support a growing number of connected devices, and to pave the way for the wider adoption of technologies like autonomous vehicles, augmented reality, and robotics. If the FCC approves Intelsat's proposal, it could be a dramatic windfall for the company, but it's uncertain how the regulatory environment will develop -- the FCC might not have final say on the matter. It's also worth keeping in mind that not all industry players are on board with the idea -- companies including T-Mobile, Alphabet, and ABS oppose it.

1. Turtle Beach: Up 1,480%

As impressive as the performances of other high-flying tech stocks have been in 2018 so far, Turtle Beach stands as the far-and-away winner when it comes to huge returns this year. The computer-and-gaming-accessory company makes keyboards, mice, and headsets -- though the headset product category accounts for most of its sales, and has been the key driver for its gains this year.

HEAR Chart

HEAR data by YCharts

Underlying its sales growth has been the explosive popularity of games in the "battle royale" genre -- namely Fortnite and PlayerUnknown's Battlegrounds. Turtle Beach is the top brand for gaming headsets, with somewhere around 40% market share, and it also stands to benefit as the esports market grows at a rapid clip. However, the massive stock gain in the rear-view mirror is also a reason for new investors to tread carefully. Shares are priced at roughly 28 times forward earnings, which is a potentially lofty valuation for a gaming-hardware company that doesn't have much in the way of a moat, and is dependent on one category of products.