Localization testing services for your global audience

Uncovers language, currency, and cultural issues before they impact your customer around the world.  

Ensure your app works flawlessly, in every market for every user.

Localizing software for dozens of languages requires finding and managing testers in critical markets with suitable devices. With Testlio’s localization testing services, you gain complete localization coverage with managed in-market testers speaking 100+ languages.

Our approach to localization QA follows three central tenets:

Tap global localization experts.

Fully vetted and fluent testers conduct functional, UI, language localization, linguistic, and translation quality testing for you.

Test on real devices in the wild.

With access to 1000s of real device/OS combinations, we uncover internationalization issues, including UI, RTL, and device-specific performance issues.

Gain human-led insights.

Our experienced testers and engagement managers identify gaps and report subtle language, cultural, technical, regional, and inclusivity factors.

Localization testing use cases

Top 5 Photo & Video App

Challenge: Ensure customers have a localized, inclusive, and culturally appropriate experience in 45+ countries.

Solution: Comprehensive app localization testing, inclusivity testing, and internationalization validation for multi-channel touchpoints: apps, web properties, app stores, marketing materials, support channels, documentation, and more.

  • 160 localization testers
  • 45+ languages
  • 370+ devices/OS combinations tested
  • Captured linguistic and sentiment feedback for a better CX

Professional Basketball Association

Challenge: Expand a U.S. professional basketball cultural offering with country-specific characteristics to accommodate local fans throughout the world.

Solution: Validate SKU and live streaming packaging in local languages/currencies plus blackout testing in key country-specific geos to ensure a flawless global fan experience.

  • 130+ localization testers
  • 70+ countries
  • 270+ device/OS combinations tested
  • Increased market share with localized offering

Top OTT Streaming Media Platform

Challenge: Our client’s in-house QA team exceeded its capacity for localization verification for applications and packaging as the company expanded into EMEA, AMER, and APAC countries.

Solution: Testlio created localization and bug verification workflows and conducted tests for native language subs and dubs voice testing within critical markets.

  • 50+ localization testers
  • 10+ languages
  • 45+ device/OS combinations tested
  • Prevented churn by enabling users to engage in their preferred language

Testlio has made our user experience a competitive advantage. They ensure our app meets customers’ expectations no matter where they are located or what device they are on.

Mark Shaw, CTO (and co-founder), Strava

What We Test

Localization software testing ensures your app adapts to a global audience.

Functional Localization Testing

  • UI localization issues such as elements overlapping and truncations
  • App functionality, including matching translations to UI functions
  • Untranslated texts
  • Inclusive by design validation

Language Testing

  • Grammar, spelling, punctuation issues, and inaccurate translations
  • Currency, symbols, pricing, and payments
  • RTL evaluation
  • Client-specific app terminology

Linguistic & Translation Testing

  • Unnatural translations
  • Quality and consistency, such as specific words translated the same across the app
  • Idiomatic testing, ensuring consistent tone and giving content feedback on cultural relevance and accuracy

Case Studies & Resources

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Fitness app increases in release cadence by 6x

How Strava’s fitness tech platform conducted mobile app localization testing in 12 languages to gain global market share. 

Localization testing goes beyond languages

Localization testing services need to understand UI elements affected by language as well as the language of design elements.

Localization testing is critical to ensuring global brand consistency

Localization testing goes beyond functionality and dives into cultural nuance. Here’s a quick guide.

What to expect from Testlio


Rapid tester selection and management aid in more predictable releases for product and engineering teams.


Testing at a global scale supports market expansion and growth via exceptional localized experiences.


Compared to in-house, outsourced, and traditional crowdsourced testing models, Testlio delivers unbeatable value.

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See Testlio’s approach to software localization testing