A second screen is the smaller personal device, almost always a smartphone, that a person uses while watching television. The term describes a behaviour rather than a product. Attention divides between a large shared display and a private one, and the private device holds the keyboard, the payment credentials and the app logins. That asymmetry is the whole point for advertisers: television carries the message, and the second screen carries the response. Where the two devices cannot be linked, the response is recorded as organic traffic and the television budget receives no credit for it.

What viewers actually do with the second device

Simultaneous use is now close to universal in survey data. A MiQ study drawing on 53 million households found that 91% of consumers use a second device while watching television, with half of that group juggling multiple devices most of the time. The single most common pairing was connected television plus a mobile phone, covering 69% of respondents. Activity splits roughly two ways: 43% used the second device for social media, news or other video, while 22% were researching products related to the programme on the main screen.

Earlier LG Ad Solutions research found 95% of connected television viewers multitasking, with 26% doing so always, an eight-point year-on-year rise. The activity breakdown there was messaging at 62%, social media at 54%, gaming at 47%, online shopping at 44% and streaming other content at 24%. Post-exposure behaviour was measured separately: 39% searched for a product online after a relevant advertisement, 38% visited a website, 21% bought something and 19% visited a physical store.

Live programming concentrates the effect. A 2025 study cited by the Coalition for Innovative Media Measurement reported that 86% of Formula 1 fans use a second screen during races, and the body listed measuring second screen usage among nine unsolved challenges in sports audience measurement.

Three ways the screens get connected

The simplest method is no connection at all. An advertiser runs television, watches branded search volume and direct site traffic rise, and infers causation from timing or from a geographic holdout. Nothing on the phone knows the television advertisement ran.

The second method is a visible bridge, usually a QR code, a scannable square barcode carrying an encoded URL with campaign parameters. Google added QR code call-to-action overlays to non-skippable YouTube advertisements on connected TV through Display and Video 360's Instant Reserve function in May 2024. By 2026 the codes were being generated automatically from Merchant Center product feeds in shoppable connected TV formats, with the destination set by the product link in the feed. Supply-side platforms built comparable inventory: TripleLift shipped Enhanced Spots carrying QR codes alongside Split Screen, Dynamic Overlay and L-Bar formats, launched with DIRECTV and extended to Plex and Xumo in November 2025.

The third method is machine identification. Automatic content recognition, abbreviated ACR, samples the audio or video a television is displaying, converts the sample into a fingerprint and matches it against a reference database, producing a continuous log of what a set showed and when. Because the log carries a household IP address, it can be joined to mobile devices on the same network. LG Ad Solutions placed a dataset drawn from more than 33 million opted-in sets on the Databricks Marketplace on October 22, 2025. Nexxen licensed ACR audience segments to Yahoo DSP across the United States, United Kingdom and Germany on October 16, 2025.

The synchronisation specifications

Broadcast standards define a formal version of the link, and the vocabulary there is companion screen rather than second screen. The Hybrid Broadcast Broadband TV Association, HbbTV, released version 2.0 on February 10, 2015, adding companion device support, remote application launch and inter-device media synchronisation. The underlying protocol suite is DVB Companion Screens and Streams, published by the European Telecommunications Standards Institute as TS 103 286.

Part 2 of that specification defines the interfaces a television exposes. CSS-CII carries content identification and other information, and is the entry point a companion application connects to first. CSS-MRS resolves content identifiers to material. CSS-WC establishes a shared wall clock between television and companion, compensating for network latency and jitter through a request and response exchange. CSS-TS synchronises a timeline so the companion knows the exact playback position. CSS-TE delivers trigger events. Discovery and association, CSS-DA, is covered in part 3 and built on UPnP device architecture. Part 2 has been revised twice, to V1.2.1 in August 2017 and V1.3.1 in January 2022. The BBC published open-source client implementations in Python, JavaScript and iOS.

Origin and evolution

Measurement of the behaviour predates the advertising formats built for it. Nielsen published Double Vision in April 2012, based on a fourth-quarter 2011 survey of connected device owners in the United States, United Kingdom, Germany and Italy. It found 88% of American tablet owners and 86% of American smartphone owners had used the device while watching television at least once in the preceding 30 days.

Google followed on August 29, 2012 with The New Multi-Screen World, which distinguished sequential screening, a task moving between devices over time, from simultaneous screening. The study reported that 90% of media interactions were screen-based, that leisure screen time averaged 4.4 hours a day, and that 77% of television viewers had another device in hand.

Standards work split along two lines. W3C chartered the Second Screen Presentation Working Group in October 2014 to develop the Presentation API, and the HbbTV and DVB route produced the companion screen protocols in 2015. Dedicated social television applications, the visible face of the category in 2012 and 2013, largely disappeared once general-purpose social platforms absorbed the conversation.

Advertising caught up later. Coinbase aired a 60-second Super Bowl LVI spot on February 13, 2022 showing only a bouncing QR code, and chief product officer Surojit Chatterjee said the landing page took more than 20 million hits in one minute, enough to force brief traffic throttling. The advertisement finished last in the USA Today Ad Meter rankings for that game, and remains the reference case for second-screen response at scale.

Why the term matters commercially

The second screen is where connected television's attribution problem lives. An impression is delivered to one device and the conversion happens on another, with no shared identifier by default. If nearly all viewers are simultaneously active elsewhere, deciding which screen caused a purchase becomes materially harder, and the MiQ research noted that 71% of consumers get distracted during product research and only return when prompted.

Buyers treat the gap as a cost. Research from the Interactive Advertising Bureau, IAB, published on July 14, 2026 found 43% of connected TV buyers lacking confidence in where their advertisements ran, with second-device friction and limited shoppable format scale named as the leading lower-funnel obstacles. Consumer packaged goods, retail, fashion and consumer electronics advertisers cited the shoppable scale problem at 45%.

Limitations and disputes

Nearly every headline figure on second screen use is self-reported. Panel observation produces a less flattering picture: TVision measurement found that only nine of roughly 200 daily viewing minutes count as attentive advertisement time.

Response counts are also softer than they look. Landing page hits, QR scans and people are three different quantities, and the Coinbase figure was hits reported by the advertiser, not independently verified scans.

The direction of the effect is contested. The Video Advertising Bureau and TVision reported co-viewing at 60% on premium video against 45% on YouTube, treating engagement quality as platform-dependent. A Magnite survey in Hong Kong found near-parity in unaided recall between connected television at 47% and smartphone at 45%, a result that undercuts the assumption that the large screen delivers stronger recall.

The ACR bridge carries legal exposure. Texas sued Hisense in December 2025 over smart television data collection affecting roughly 470,000 households, alleging the company labelled its ACR system Enhanced Viewing Service during setup and disclosed the actual term only after extensive navigation. Court filings cited in the case argued the data collected was worth as much as the televisions themselves.

Adjacent terms

Co-viewing counts several people watching one screen, which inflates reach against a single impression. Second screen counts one person using two devices. The two effects run in opposite directions.

Companion screen is the standards-body term for a device formally synchronised to a broadcast through DVB CSS. Every companion screen is a second screen; almost no second screen is a companion screen.

Second screen in W3C usage is inverted. In the Presentation API, the second screen is the presentation display being cast to, typically the television, with the phone as the controller.

Multiscreen or cross-screen describes buying a campaign across devices. It concerns media planning, not simultaneous use.

Recent developments

Platforms have started removing the second screen rather than measuring it. At Brandcast on May 13, 2026, YouTube introduced two-click checkout on the television itself through Google Pay, explicitly to eliminate the hop to a phone. On June 22, 2026, Samsung Ads and Amazon Ads made Samsung TV Plus advertisements addable to an Amazon cart using the remote control, the first deployment of Amazon's interactive video technology on third-party free ad-supported streaming inventory. KERV.ai and LG Ad Solutions extended object-detection shoppable formats into Canada, Europe, Australia and New Zealand in August 2026, triggering interaction from recognised content rather than a fixed placement.

Whether that closes the loop or removes the only measurable bridge remains open. QR codes at least produced a click with parameters attached. A purchase completed on the television using stored credentials produces a conversion inside a platform's own reporting.

Timeline

  • Fourth quarter 2011: Nielsen surveys connected device owners in four markets for the study later published as Double Vision
  • April 2012: Nielsen reports 88% of US tablet owners and 86% of US smartphone owners using devices while watching television within a 30-day window
  • August 29, 2012: Google publishes The New Multi-Screen World, recording 77% simultaneous device use during television viewing
  • October 2014: W3C charters the Second Screen Presentation Working Group to develop the Presentation API
  • February 10, 2015: HbbTV Association releases HbbTV 2.0 with companion screen and inter-device synchronisation support
  • May 2015: ETSI publishes DVB Companion Screens and Streams as TS 103 286, defining the CSS-CII, CSS-WC, CSS-TS and CSS-TE interfaces
  • August 2017: ETSI TS 103 286-2 revised to V1.2.1
  • December 2018: Nielsen reports 45% of US adults using a second screen very often or always
  • January 2022: ETSI TS 103 286-2 revised to V1.3.1
  • February 13, 2022: Coinbase airs a bouncing QR code advertisement during Super Bowl LVI
  • May 2024: Google enables QR code overlays in non-skippable YouTube connected TV advertisements via Instant Reserve
  • October 16, 2025: Nexxen licenses ACR segments to Yahoo DSP in three markets
  • October 22, 2025: LG Ad Solutions publishes ACR viewership data on Databricks Marketplace
  • December 2025: Texas files suit against Hisense over smart television ACR data collection
  • May 13, 2026: YouTube announces two-click connected TV checkout at Brandcast
  • June 22, 2026: Samsung Ads and Amazon Ads launch remote-controlled cart additions on Samsung TV Plus
  • July 14, 2026: IAB reports 43% of connected TV buyers lacking confidence in placement

Summary

Who: Viewers holding phones during television, and the advertisers, measurement firms, smart television manufacturers and standards bodies attempting to connect the two devices. Nielsen and Google produced the founding measurement work; HbbTV, DVB and W3C wrote the specifications; ACR vendors including LG Ad Solutions and Nexxen supply the data layer; IAB and CIMM document the unresolved measurement problems.

What: The use of a smartphone, tablet or laptop while watching television, and the set of formats, protocols and data joins built to link exposure on the large screen to action on the small one.

When: Measured systematically from Nielsen's fourth-quarter 2011 survey and Google's August 2012 study, formalised in standards during 2014 and 2015, and turned into scaled advertising formats from May 2024 onwards.

Where: In the living room, and in the transaction flow between connected television inventory, QR overlays, ACR data licensed to demand-side platforms, and conversion reporting inside platform environments.

Why: Because television carries the message and the second screen carries the response, and the record of that response determines whether television budgets receive credit for the sales they generate.