What is 16x Eval used for?

16x Eval is a local desktop application for testing and comparing AI models and prompts. It allows you to create custom evaluations with your own prompts and contexts, score responses using predefined criteria or custom JavaScript functions, and view detailed metrics like cost, speed, and token usage. It helps you choose the best model for your specific use case.

Yes, there is a free version that includes a prompt library, context library, storage for up to 20 evaluations, metrics, evaluation functions, and local data storage. For unlimited evaluations and additional features like multi-device support and priority support, a one-time payment of $28 for a life-time license is available.

Do I need to provide API keys for models?

Yes, 16x Eval is a BYOK (Bring Your Own Key) application. You need to provide your own API keys for the model providers you wish to evaluate, such as OpenAI, Anthropic, Google, or any OpenAI-compatible provider. The app does not include API credits.

How does the life-time license work?

The life-time license is a one-time payment of $28 that unlocks unlimited evaluations, activation on up to 10 devices, invoice for purchases, and priority support. It does not expire and is tied to your purchase.

Does 16x Eval support image analysis?

Yes, you can import image contexts for evaluations. This allows you to test model performance on tasks like explaining what happened in an image, and compare how different models interpret visual content.

16x Eval

Updated Jul 26, 2026

Create custom evals to test models and prompts for your use case. Free, no sign-up. Compare models side-by-side with metrics and custom evaluation functions.

Categories:

Developer Tools|

Research|

Prompts

#ai evaluation#prompt engineering#model comparison#llm#ai benchmarking

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Editor's Verdict

Rating: 4.2/5.0•Reviewed by RAGWiki

At $0, 16x Eval stands out as a powerful solution in the developer tools,research,prompts landscape. It is especially well-suited for professionals like Software Engineer and Data Scientist. However, potential buyers should note that it might not be perfect if you are strictly trying to avoid requires own api keys. Overall, it offers a robust toolset that significantly accelerates workflows.

Key Takeaways

Prompt Evaluation
Model Evaluation
Evaluation Function
Rubrics & Human Rating

In-Depth Review: What is 16x Eval?

16x Eval provides a free, local workspace for prompt engineering and model evaluation. Easily manage prompts, contexts, and models, run evaluations across multiple models simultaneously, and compare results with detailed metrics like cost, speed, and ratings. Use simple target/penalty strings or custom JavaScript functions for automatic scoring, or define rubrics for human rating. Supports top providers (OpenAI, Anthropic, Google, etc.) and BYOK API keys. Ideal for developers, data scientists, and product leaders to optimize AI performance for their specific tasks.

Core Features

Prompt Evaluation

Manage prompts, contexts, and models locally to test different combinations with ease.

Model Evaluation

Evaluate multiple models in parallel on the same prompts and contexts.

Evaluation Function

Create custom criteria using target and penalty strings for automated scoring.

Rubrics & Human Rating

Define consistent rubrics and add notes for systematic human assessment.

BYOK API Integrations

Bring your own API keys for providers like OpenAI, Anthropic, Google, and more.

Cost Tracking

Track input/output tokens, price, cost, and throughput across evaluations.

Experiment Management

Organize evaluations into experiments with categories, archiving, and linked evaluation functions.

Tool Call Support

Support for tool call validation and advanced evaluation logic.

Side-by-Side Comparison

Compare results from different models and prompts with detailed metrics in a table.

Customizable Columns

Tailor the evaluation table to show only the most relevant metrics.

JavaScript Evaluation Functions

Write custom JavaScript for complex evaluation logic and scoring algorithms.

Local Data Storage

All data stays on your machine, ensuring privacy and security.

Benchmark Page

View and compare model performance across categories in a local benchmark.

Built-in and Custom Models

Supports top models from major providers and any OpenAI-compatible API.

Pricing

Free

Prompt library and context library
Store up to 20 evaluations
Metrics and evaluation functions
Import and export for collaboration
Local data storage for privacy

Life-time License

$28

Everything in Free
Store unlimited evaluations
Activate up to 10 devices
Invoice for purchases
Priority support

Pros and Cons

Pros

Privacy-First Local StorageAll data stays on your local machine, ensuring full control and privacy without cloud dependency.
No Sign-Up RequiredFree version requires no account creation, login, or personal information, making it easy to start.
Multi-Model SupportEvaluate and compare multiple models from various providers simultaneously, including custom OpenAI-compatible endpoints.
Flexible Evaluation CriteriaUse simple target/penalty strings or write custom JavaScript functions to score responses exactly as needed.
Comprehensive MetricsTrack cost, tokens, speed, and ratings with customizable columns for in-depth analysis.

Cons

Requires Own API KeysYou must provide your own API keys for model providers, which means you are billed separately for API usage.
Limited Free PlanThe free version only supports up to 20 evaluations, which may be restrictive for extensive testing.
No Cloud CollaborationSince data is stored locally, collaborating with a team in real-time or syncing across devices is not built-in.
Desktop-Only Application16x Eval is a local application, not a web service, so it requires installation and runs on your machine.
Uncertainty About UpdatesThe life-time license cost is low, but it's unclear if future updates require additional payment or are included.

Use Cases & Recommended Professions

Software Engineer→ View Toolkit

Evaluate AI models for coding tasks, compare code generation quality, and test prompts for code completion or feature addition.

Data Scientist→ View Toolkit

Assess model performance on data analysis and extraction tasks, compare outputs for accuracy and consistency.

Product Manager→ View Toolkit

Make informed decisions on which model to integrate into products by comparing evaluation results across use cases.

AI Researcher→ View Toolkit

Conduct systematic experiments on model behaviors, test custom evaluation functions, and analyze metrics.

Content Creator→ View Toolkit

Evaluate AI writing assistants, compare text quality for different prompts, and fine-tune for brand voice.

Prompt Engineer→ View Toolkit

Iterate on prompt designs, A/B test variations, and optimize prompts for specific model responses.

Frequently Asked Questions

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ℹ️ Curation Disclosure: The overview and features of 16x Eval were synthesized using AI and fact-checked by our curation team to ensure accuracy.