SK Telecom Releases Open-Source Korean LLM ‘A.Dot X 4.0’ with Industry-Leading Performance

SK Telecom has released its Korean large language model (LLM), A.Dot X 4.0, as open-source software, positioning it as one of the most advanced Korean-language AI models available worldwide. On July 3 (KST), the company announced the public release of two versions—standard and lightweight—on Hugging Face, a prominent open-source AI platform. The standard model comprises 72 billion parameters, while the lightweight version contains 7 billion, allowing users to select a model tailored to their specific needs.

A.Dot X 4.0 distinguishes itself with exceptional Korean language processing capabilities. Built on the Qwen2.5 open-source base model, SK Telecom fine-tuned it with a vast corpus of Korean-language data to optimize performance for domestic business applications. The model also incorporates a custom tokenizer developed in-house, which reportedly achieves approximately 33% greater token efficiency compared to OpenAI’s GPT-4o when processing Korean sentences. This translates to superior information processing and reduced operational costs.

Performance benchmarks highlight the model’s strengths. In KMMLU (Korean Massive Multitask Language Understanding), a key benchmark for evaluating Korean language proficiency, A.Dot X 4.0 scored 78.3—outperforming GPT-4o’s 72.5. In CLIcK (Cultural and Linguistic Intelligence in Korea), which assesses understanding of Korean language and culture, A.Dot X 4.0 achieved a score of 83.5, surpassing GPT-4o’s 80.2.

The model also offers advantages in data security. A.Dot X 4.0 is available for on-premises deployment, enabling businesses to install and operate the model within their own servers. SK Telecom trained the model using proprietary data through a fully internal Continual Pre-Training (CPT) process, ensuring data sovereignty while minimizing external dependencies.

SK Telecom has already integrated A.Dot X 4.0 into its A.Dot call summarization service, launched in May, and plans to extend its use across other SK Group services. Companies can use the released models to develop custom derivative models or apply them in academic research.

In addition to the knowledge-type model release, SK Telecom is preparing to unveil a reasoning-type model later this month. This upcoming version will feature enhanced mathematical and coding capabilities and will support multimodal processing—understanding and generating both images and text. The company is also continuing its “from scratch” development strategy, used in A.Dot X 3.0, as part of its sovereign AI initiative, with further model iterations expected in the near future.

The original article is available on SKT Newsroom.