What is Vellum?

Content last verified May 4, 2026 · by the AI Tools Set Research Team

Vellum is a development platform for building production LLM applications, with tools for prompt engineering, testing, evaluation, and deployment. It offers a prompt playground, version control, and workflows for shipping reliable AI features.

Product and engineering teams use it to move prompts from experimentation to production with proper testing and monitoring.

Key Features of Vellum

Prompt playground: Experiment across models.
Testing and evals: Validate prompt quality.
Version control: Manage prompt changes.
Workflows: Chain prompts into apps.

Use Cases for Vellum

Build LLM features
Test prompts
Deploy to production
Evaluate quality
Manage prompt versions

Pros & Cons

Pros

✓

End-to-end LLM dev

✓

Strong testing

✓

Workflows

✓

Multi-model

Cons

✗

Developer and team focus

✗

No permanent free plan

Pricing

Free Trial

✓Playground

✓Limited features

✓Preview