Appen alternatives: 6 tools compared (October 2026)

Kili Technology is an annotation platform for building AI training datasets across images, video, text, documents, geospatial imagery and audio, with AI pre-labeling, quality control and optional labeling services.

Key functions

• AI-assisted pre-annotation, with SAM 2 for images
• Quality control and performance tracking for annotation teams
• Annotation for image, video, text, OCR, geospatial data and audio in one tool

Compared with Appen

• Offers a free trial; we found none for Appen.
• Headquartered in France, Appen in Australia.
• Targets companies under 50 employees, which Appen does not.

Check before buying: Plans above the free tier are priced by seats and assets on request, so estimate volumes first. Clarify the hosting region, since the pricing page mentions specific cloud regions without naming them. SSO and on-premise deployment are Enterprise features. Sign a data processing agreement before labeling personal data.

Prolific connects AI developers, researchers and companies with verified participants who provide human data, from preference judgments for model training to evaluations of AI agents and academic studies.

Key functions

• Human feedback for preference tuning and safety evaluations of AI models
• Domain experts such as healthcare and software engineering for demanding tasks
• Evaluation of AI agents and models with representative participants

Compared with Appen

• Publishes a price; Appen quotes on request.
• Headquartered in United Kingdom, Appen in Australia.
• Targets companies under 50 employees, which Appen does not.
• Different pricing model: usage-based instead of contact for pricing.

Check before buying: Budget both participant rewards and the platform fee, which is 42.8 percent for companies. Specialized tasks need higher pay to attract qualified people. Avoid putting personal or confidential data into tasks unless your agreement covers it, and request the data processing terms.

Scale AI provides training data, human feedback and evaluations for companies that build AI models, and develops AI applications for large enterprises and government agencies.

Key functions

• Data Engine delivers labeled training data and human feedback for model builders
• Evaluation services and private leaderboards for model capabilities
• GenAI Platform for enterprise AI applications

Compared with Appen

• Names 4 security certificates, Appen 2.
• Strongest elsewhere: United States.

Check before buying: Scale publishes no prices, so request a quote per project and clarify how contributor work is quality-checked. Clarify where data is stored and who among the global contributor network can see it. Request the SOC 2 report through the trust center and a data processing agreement before sharing personal data.

Toloka supplies human-generated training and evaluation data for AI agents and large language models, drawing on a network of domain experts, for AI labs and companies building their own models.

Key functions

• Agent trajectory demonstrations and step-by-step evaluations for training AI agents
• Virtual environments for reinforcement learning
• Red teaming to test models for vulnerabilities

Compared with Appen

• Headquartered in Netherlands, Appen in Australia.
• Strongest elsewhere: Netherlands.

Check before buying: Toloka publishes no price list, so define scope and quality targets for a quote. Clarify storage location, since the platform runs on Azure with several options. Check which contributors in which countries see your data and sign a data processing agreement with Toloka AI B.V.

Arena is a public platform where people compare two anonymous AI answers and vote for the better one. The votes feed leaderboards that many teams consult when choosing a model.

Key functions

• Anonymous side-by-side comparisons of two model answers with user votes
• Leaderboards per category from text and WebDev to text-to-video
• Pareto view of price versus performance per task

Compared with Appen

• Targets companies under 50 employees, which Appen does not.
• Strongest elsewhere: United States.

Check before buying: Anything typed into Arena may be published and shared with AI providers, according to its privacy policy, so staff must not enter company, customer or personal data. Crowd preferences favor style and tone and do not replace tests on your own tasks. Arena Intelligence is headquartered in the United States, and according to the privacy policy personal data may be transferred to the US or other countries.

Label Studio is an open-source data labeling tool for ML and AI teams that annotate text, images, audio, video and agent traces. HumanSignal, which maintains it, sells cloud and enterprise editions with automation and evaluation features.

Key functions

• Pre-labeling through connected ML models (ML backend)
• LLM-based pre-labeling, limited on Starter Cloud
• LLM-as-a-judge evaluation with human review in the Enterprise edition

Compared with Appen

• Publishes a price (from $99 per month); Appen quotes on request.
• Targets companies under 50 employees, which Appen does not.

Check before buying: The Community Edition has no compliance reporting and must be operated, updated and secured by your own team. Starter Cloud includes only limited LLM pre-labeling; SSO, full LLM-as-a-judge evaluation and on-premises deployment are Enterprise features. For the cloud editions, clarify hosting region and data processing terms before labeling personal data.