*This is the sixth instalment of our series examining AI apps and services making waves in South Korea.*

Introduction

Santa is an AI-driven test-preparation app for TOEIC and TOEFL, operated by Socra AI (formerly Riiid). The service has had an identity of sorts: it briefly rebranded as "Riiid Tutor" in June 2021 before reverting to its original name. With more than seven million registered users and over 600 million accumulated learning data points, Santa's central proposition is a personalised curriculum tailored to each individual learner.

Core Features

Santa's diagnostic approach is notably sophisticated. New users begin with a 12-question assessment designed to pinpoint their current ability as efficiently as possible. From there, the app continuously analyses real-time learning data to chart an optimal study path. According to the company, Santa's AI can identify *why* a user answered a question incorrectly with 95% accuracy—going well beyond simple right-or-wrong scoring to identify the underlying cause, whether that is a gap in conceptual understanding, poor time management, or a recurring weakness with a particular question type.

The app recently added "Santa Lumi," a TOEIC-specialist GPT-based assistant that allows users to ask questions and receive explanations around the clock. A dedicated curriculum targeting a score of 800 is also available for complete beginners. Santa has also expanded into TOEFL preparation this year, formally launching an AI TOEFL service aligned with the revised January 2026 exam format. The service uses official questions from ETS—the body that administers TOEFL—and applies ETS-developed automated scoring technology to evaluate written responses. Users can switch seamlessly between mobile, tablet, and desktop, with progress synced across all devices under a single account.

Strengths and Limitations

Santa's greatest strength lies in the depth of its data-driven personalisation. Rather than simply flooding users with practice questions, the app recommends only the question types most relevant to each learner's specific weaknesses. This targeted approach is particularly well-suited to working professionals and job-seekers who have limited time to prepare. The company reports that CB Insights has ranked it among the top two global edtech firms in the education category, and it runs ongoing score-guarantee challenges in which users receive a refund if they fail to reach their target score—a meaningful incentive.

There are limitations. Some users have reported being unable to log into their existing Korean accounts when accessing the service from abroad, suggesting unresolved issues with cross-border account compatibility. Android users have also flagged app crashes frequently enough that the customer support FAQ includes a dedicated entry on the problem—a sign that the user experience still has room for polish. The marketing headline of "an average 165-point improvement in one hour a day" also warrants scrutiny: such figures are based on specific conditions, including first-time purchases and peak scores achieved within the subscription period.

Verdict

Santa is among the most battle-tested AI edtech services in South Korea. Where other apps reviewed in this series—such as conversational AI tools or messenger-integrated assistants—serve broad or general-purpose needs, Santa is distinctive in its singular, practical focus: optimising a learner's path towards a measurable exam score. Because test results provide an unambiguous benchmark, this is perhaps the category in which the value of AI assistance is easiest to feel and verify.

★★★★☆ (4.0/5.0)

In a sentence "An AI that can diagnose why you got it wrong—just don't expect the app itself to run without the occasional hiccup."