In the last few years, OTT services have taken the world by storm, giving users access to countless content choices at their fingertips. OTT describes services and technology that enable streaming of video Over The Top of high speed internet to connected devices.

According to Statista, the global OTT services market size is projected to reach US $343.8 billion in 2025 with an annual growth rate (CAGR 2025-2029) of 6.56%. 

OTT giants such as Netflix, Amazon Prime, Hulu, Disney+ Hotstar, STC TV, and others offer a variety of content with top-notch quality.

To deliver an app with a seamless, high-quality experience for end-users, a series of tests must be performed. OTT testing checks whether a streaming app delivers smooth audio and video across all supported devices.

Let’s get into the checklist

This OTT testing checklist covers the key tests we use to measure the functionality, performance, and quality of OTT streaming services.

• UI/UX Testing
• Compatibility Testing
• Network Testing
• Performance and Load Testing
• Localisation Testing

UI/UX Testing 

A flawless and intuitive UI is key to our applications making a great impression on a user’s first visit, which will keep them coming back. We need to ensure that the app is designed for a seamless user experience.

Below are the steps we take for UI/UX testing:

• Verify every screen, layout, font, theme, error or success message, against the Figma designs (or wireframes) provided by the design team.
• Ensure the interface adapts properly to different screen sizes and resolutions (smart TVs, tablets, smartphones, and desktops).
• Test how easy it is to navigate menus and categories. Validate that users can easily find and access content.
• Check how prominently key elements, such as featured content, the search bar, or an upcoming World Cup tournament, are displayed.
• Check the placement of buttons and controls.
• Ensure that the text is readable.
• Test the app for accessibility compliances which follow standard guidelines.
• Verify the application in multiple languages to ensure no overlaps or breaks.
• If the app is a popular platform for watching sports, films, sitcoms, and other content, ensure the UI handles every type within one consistent theme and shows no design irregularities.

Functional Testing

Among other things, we make sure that the different functional areas of the app work correctly, depending on the requirements. Below are a few specific points from our checklist:

• Ensure that users can seamlessly sign up and login from all possible checkpoints, such as shared links, search-engine results, and native app integration points.
• Verify that region-specific content is available based on geographic mapping. For example, if a movie is released only in China, users in other regions should not be able to view or play it.
• Validate that searching for content is easy and flawless, and that the app retains search history across all platforms. 
• Test different user journeys, such as guest user registration, profile creation, subscription purchase, content access and playback, and validate every possible flow and variation. 
• Users should be able to add any content to their favourites and access it again from their My List or My Favourites page.
• An interactive loading state should appear throughout the app.
• Live and On Demand playback should be smooth.
• Any errors should be handled by the app, showing a clear message on the UI and providing a retry option.

Player Testing

At the heart of every OTT service is the app player – the interface through which users experience content. Whether it’s a movie, TV show, or live event, the OTT app player is the key point of interaction, responsible for smooth video playback, responsive controls, and an intuitive user experience. 

That’s why we verify functionality, performance, and usability of the media player to ensure high-quality audio and video remain consistent throughout playback and whenever any player feature is used. 

We verify the below as part of our checklist:

• Test different resolutions – SD, HD, and 4K – across platforms, including smart TVs, mobiles, streaming sticks, and the web.
• Ensure audio, video, and subtitles are in sync.
• Verify that playback functions – pause, mute, volume adjustment, seeking and language switching – work correctly.
• Confirm that content streams correctly from the CMS and that video quality adapts to both network conditions and device capabilities.
• Test buffering strategies under varying conditions and confirm that manual video-quality changes work correctly.
• Check that watch-party features work correctly, that VOD transitions after live programmes are seamless, and that Chromecast and Airplay are supported.
• Test extended playback sessions for consistent quality and minimal lag.
• Ensure smooth ad-content transitions.

Compatibility Testing

Compatibility testing determines whether the application functions as designed across all supported browsers, devices, and operating systems. To measure this, we use the following checkpoints:

• Test across smartphones, tablets, iPads, smart TVs, Firesticks, different browsers, and any other supported platforms.
• Check multiple versions of operating systems and browsers based on market usage.
• Verify across different TV device versions, for example, Samsung TV 2021, 2022, 2023 and 2024.
• Test both the beta version and the latest upgraded version of each OS.
• Ensure uniform UI across platforms.

Additionally, we ensure that all compliance requirements are met for our app. For example, Samsung and LG have specific checklists to make sure that applications run smoothly on their respective TV devices. It is critical to verify that those checklist points are met, otherwise the app may be rejected.

A few commercial device farm applications – such as Browserstack and LambdaTest –  help with compatibility testing. You can explore these to determine which best suits your requirements and platform.

Network Testing

With OTT apps available across diverse geographic areas, we must ensure that the app remains stable even in poor network conditions. Here’s how:

• Use network emulation tools to replicate various network conditions (e.g., 3G, 4G, 5G, Wi-Fi).
• Test from different geographic regions to validate app performance under various scenarios.
• Emulate a mobile user scenario and confirm minimal lag or buffering. 
• Additionally, verify that the app can handle a ‘No Network’ scenario gracefully, offering a retry mechanism once connectivity returns.
• Ensure that the reload time, after connectivity is restored, remains minimal.
• Check whether the app detects a VPN and responds accordingly. 

For iOS, the simplest way to throttle the network is using Xcode on an Apple Mac device.

We can also configure the Charles Throttler in Charles Proxy, to adjust response times and bandwidth on both Android and iOS.

Performance and Load Testing 

OTT apps are content-heavy. It is therefore paramount that we do not compromise on app performance. A few checkpoints we follow include: 

• Application pages should load within a reasonable time (around 2-3 seconds).
• Content thumbnails should load within an acceptable time (around 2-3 seconds).
• Playback should start within 2 – 3 seconds. This breaks down into:
  • Time taken for player to open
  • Time taken for first frame to play 
  • Time taken when user is seeking
  • Time taken for a forwarded or rewound frame to load
• Hover-state actions, such as trailer playback, should begin within an acceptable time (around 2-3 seconds).
• Search results should load accurately within 2 – 3 seconds.

For global sports, like football, which draw millions of viewers, we ensure our app can handle high traffic and extended use. We utilize performance tools to prevent disruptions.

One of the tools we use for checking app performance at DIAGNAL is k6, an open-source tool for load and performance testing on APIs, microservices, and websites. 

In addition to k6, we use Firebase Performance Monitoring to gain insights into the performance characteristics of Apple, Android, and web apps. The Performance Monitoring SDK collects performance data, which we then review and analyse in the Firebase console.

Localisation Testing

Today, most OTT applications serve global audiences, offering content suited to regional preferences and needs. When building such an application, we ensure it meets those region-specific requirements.

To achieve this,  we check the following:

• Validate the app’s language support, ensuring content, labels, and error messages load correctly for all supported languages.
• Ensure the app detects the device language and translates all text accordingly. For profile-specific language selections, we make sure the app remembers the user’s choice.
• In regions with content blocks, we check that content access is restricted.
• Verify regional formatting for dates, times, currencies, and numbers.
• Thumbnails align with the user’s region.
• For languages like Arabic, ensure right-to-left alignment is supported without any UI breaks, and that translations apply to all content, including Privacy Policies and Terms of Service.

That wraps up Part 1 of our OTT testing Checklist, covering everything from design and functionality to performance and localisation. These first stages lay the groundwork for a stable, responsive, and user-ready platform.

Stay tuned for Part 2, where we cover subscriptions, security, geoblocking, analytics, and more.

In the meantime, if you’re building or scaling an OTT platform and want to get it right – every time – we’d love to help. At DIAGNAL, we bring this testing approach to life for major media partners across the world including Celestial Tiger Entertainment, Intigral, Lounges.TV, Optus Sport, WRC Promoter, and others.

Reach out to us today for the support you need.