Weights & Biases is the clear choice for teams evaluating MLOps experiment tracking platforms in 2026. While Neptune.ai was a strong contender for foundation model training workflows, its acquisition by OpenAI in December 2025 means it is no longer available as an independent product. Weights & Biases offers a comprehensive feature set spanning experiment tracking, AI application evaluation, model registry, and team collaboration with transparent pricing starting from a generous free tier.
| Feature | Neptune.ai | Weights & Biases |
|---|---|---|
| Best For | Foundation model training at scale | Full ML lifecycle tracking and collaboration |
| Pricing Model | Contact for pricing | Free (Free tier), $60/mo (Pro), CONTACT US (Enterprise) |
| Free Tier | Not available (acquired by OpenAI) | Yes — up to 5 model seats, 5 GB/month storage |
| Open Source | No | Yes (MIT license, 11,000+ GitHub stars) |
| Deployment | Cloud-hosted | Cloud, self-hosted, and on-premise options |
| Metric | Neptune.ai | Weights & Biases |
|---|---|---|
| GitHub stars | — | 11.0k |
| TrustRadius rating | — | 10.0/10 (2 reviews) |
| PyPI weekly downloads | 45.8k | 5.6M |
| Search interest | 1 | 0 |
| Product Hunt votes | 6 | — |
As of 2026-05-04 — updated weekly.
| Feature | Neptune.ai | Weights & Biases |
|---|---|---|
| Experiment Tracking | ||
| Run logging and visualization | Yes — optimized for months-long training runs | Yes — tracks architecture, hyperparameters, git commits, model weights, GPU usage |
| Metric comparison at scale | Yes — compare thousands of metrics in seconds | Yes — compare and visualize metrics across experiments |
| Multi-step and branching support | Yes — tracks training with multiple steps and branches | Limited — standard run-based tracking |
| Collaboration and Team Features | ||
| Team collaboration | Available at enterprise level | Yes — unlimited teams on Pro plan |
| Access controls | Enterprise-level access management | Team-based access controls (Pro), custom roles (Enterprise) |
| Service accounts | Not specified | Yes — available on Pro and Enterprise plans |
| AI Application Support | ||
| AI application evaluations | ❌ | Yes — included in Free tier |
| AI application tracing | ❌ | Yes — included in Free tier |
| Registry and lineage tracking | Not specified | Yes — asset registry and lineage tracking included |
| Infrastructure and Deployment | ||
| Self-hosted deployment | Not publicly available | Yes — run locally with Docker and Python |
| HIPAA compliance | Not specified | Yes — available on Enterprise plan |
| Single Sign On (SSO) | Not specified | Yes — available on Enterprise plan |
| DevOps Integration | ||
| CI/CD automations | Not specified | Yes — included in Free tier |
| Alerts and notifications | Not specified | Yes — Slack and email alerts on Free tier |
| Audit logs | Not specified | Yes — available on Enterprise plan |
Run logging and visualization
Metric comparison at scale
Multi-step and branching support
Team collaboration
Access controls
Service accounts
AI application evaluations
AI application tracing
Registry and lineage tracking
Self-hosted deployment
HIPAA compliance
Single Sign On (SSO)
CI/CD automations
Alerts and notifications
Audit logs
Weights & Biases is the clear choice for teams evaluating MLOps experiment tracking platforms in 2026. While Neptune.ai was a strong contender for foundation model training workflows, its acquisition by OpenAI in December 2025 means it is no longer available as an independent product. Weights & Biases offers a comprehensive feature set spanning experiment tracking, AI application evaluation, model registry, and team collaboration with transparent pricing starting from a generous free tier.
Choose Weights & Biases if:
Choose Neptune.ai if:
This verdict is based on general use cases. Your specific requirements, existing tech stack, and team expertise should guide your final decision.
OpenAI announced a definitive agreement to acquire Neptune.ai in December 2025. The acquisition integrates Neptune's experiment tracking tools into OpenAI's internal training stack. As a result, Neptune.ai is no longer available as a standalone commercial product for general use.
Yes. Weights & Biases offers a Free plan that includes up to 5 model seats, 5 GB/month of storage, experiment tracking, AI application evaluations and tracing, registry and lineage tracking, CI/CD automations, and Slack and email alerts. The free tier covers personal and small-scale use.
The Weights & Biases Pro plan starts at $60 per user per month billed monthly. It includes all Free tier features plus unlimited teams, team-based access controls, service accounts, and priority email and chat support. Pro is designed for early-stage teams with fewer than 50 employees.
Yes. Weights & Biases supports self-hosted deployments. You can run a W&B server locally on any machine with Docker and Python installed. The Enterprise plan adds options for single-tenant deployment with choice of region, secure private connectivity, and customer-managed encryption keys.
Neptune.ai was specifically built for monitoring months-long foundation model training runs with multiple steps and branches. However, since OpenAI acquired Neptune in December 2025, it is no longer available as a standalone product. Weights & Biases is the practical choice today, offering robust experiment tracking across the full ML lifecycle with broad framework support for PyTorch, TensorFlow, Keras, and JAX.