Sigma

Sigma AI is an enterprise-grade data annotation and AI training data provider offering custom-priced managed services typically ranging from $0.02 to $0.20 per annotation unit depending on task complexity, with RLHF and expert evaluation projects commanding premium rates of $25–$80 per annotator-hour.

Founded in 2014 and headquartered in Germany, Sigma has grown to a distributed workforce of over 6,000 annotators, linguists, and subject-matter experts operating across 25+ countries. The company supports more than 60 languages and dialects and has completed annotation projects for over 200 enterprise clients spanning technology, automotive, e-commerce, healthcare, and financial services. In 2025, Sigma expanded its generative AI evaluation practice, adding dedicated red-teaming and safety assessment services for large language models and multimodal systems, and announced partnerships with multiple European AI labs focused on sovereign AI development.

Sigma's core offering centers on human-in-the-loop data services for the full AI development lifecycle. This includes training data creation, where annotators label text, images, audio, and video according to client-defined taxonomies; model evaluation, where human raters assess the quality, safety, and accuracy of AI-generated outputs; and reinforcement learning from human feedback (RLHF), where expert annotators rank and compare model responses to fine-tune large language models. The company works across natural language processing, computer vision, speech recognition, and multimodal AI applications.

What sets Sigma apart from many competitors is its deep focus on linguistic and cultural expertise. Rather than relying solely on general-purpose crowd workers, Sigma recruits native speakers and domain specialists who understand regional context, idiomatic expressions, and cultural nuance. This is particularly valuable for companies building AI products that must perform accurately across diverse global markets. The company maintains dedicated project teams for enterprise clients, providing consistent quality and domain-specific knowledge retention across long-running annotation campaigns.

Sigma serves enterprise clients with a managed-service model, meaning clients work with dedicated project managers and quality assurance teams rather than self-serve platforms. Minimum project engagements typically start at $5,000–$10,000, positioning the service for organizations with complex, high-volume, or sensitive data labeling requirements. As of early 2026, the company has significantly expanded its RLHF and evaluation capacity to meet surging demand from AI labs developing frontier models, reporting over 150% year-over-year growth in its generative AI services division.

Headquartered in Germany, Sigma operates globally with annotators and project teams distributed across multiple continents. The company has built its reputation on handling linguistically complex and culturally sensitive annotation tasks that require more than commodity-level crowd work.