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Machine Learning · head to head

Neptune.ai vs PromptLayer

Neptune.ai logo

Neptune.ai

Machine Learning

Metadata store for MLOps

From
Free
Free plan
Yes
Full reviewWebsite
PromptLayer logo

PromptLayer

AI

Collaboration platform for prompt management, evaluation, and observability

From
Free
Free plan
Yes
Full reviewWebsite

The short version

  • Each has a real cost: Neptune.ai free tier limited to 100 hours per month, exhausted quickly with serious ML work; PromptLayer the free plan is capped at only 2,500 requests per month, quite limited for active production use.
  • They diverge on capability: Neptune.ai covers Experiment tracking, PromptLayer covers Visual prompt management.
  • Prices and features above were last checked on 30 August 2026.

Where they differ

Only the attributes on which Neptune.ai and PromptLayer actually diverge.

Attributes where Neptune.ai and PromptLayer differ
AttributeNeptune.aiPromptLayer
Pricing modelUnknownfreemium
PlatformsWeb, Self-hostedweb, api
CategoryMachine LearningAI
Founded2017Unknown

Identical on both: starting price (Free), free tier (Yes), user rating (Not yet rated).

What each one covers

Drawn from each product's published feature list. An absence here means we hold no record of it - not that the product lacks it.

Only in Neptune.ai

  • Experiment tracking
  • Model registry
  • Metadata logging
  • Comparison views
  • Custom dashboards
  • PyTorch
  • TensorFlow
  • Keras

Only in PromptLayer

  • Visual prompt management
  • Agent observability
  • Evaluations
  • Version control
  • Cost and latency monitoring
  • Agent workflow tracing

What people use each for

The jobs each tool is most often brought in to do.

Neptune.ai

  • Machine learningnot PromptLayer
  • Data analysisnot PromptLayer
  • Model trainingnot PromptLayer
  • Predictive analyticsnot PromptLayer

PromptLayer

  • Versioning and deploying prompts without code redeploysnot Neptune.ai
  • Running evaluations with human review before production releasenot Neptune.ai
  • Tracing multi-step agent workflows for debuggingnot Neptune.ai
  • Monitoring LLM cost and latency by featurenot Neptune.ai

Where each one falls short

Documented limitations, not opinions. Every one is a constraint you would hit in normal use.

Neptune.ai

  • Free tier limited to 100 hours per month, exhausted quickly with serious ML work
  • Lacks hyperparameter sweeps compared to Weights and Biases
  • No pipeline orchestration or broader MLOps lifecycle management
  • Dashboard visualization limitations - automatic resizing affects visualization order and size
  • Cloud-based SaaS only (as of last available service) requires internet connectivity

PromptLayer

  • The free plan is capped at only 2,500 requests per month, quite limited for active production use.
  • The Team plan jumps to $500/month, a large step up from the $49/month Pro plan.
  • Overage transaction fees apply on top of subscription costs, which can make total spend less predictable.
  • Enterprise-grade features like HIPAA BAAs and custom deployment require contacting sales.

Pricing, plan by plan

Neptune.ai

Free

No published plan breakdown. See the Neptune.ai review.

PromptLayer

Free
  • FreeFree
    • 5 users
    • 2,500 requests/month
    • 1 workspace
  • Pro$49/month
    • Unlimited playgrounds and workspaces
    • 150MB datasets
    • Pay-as-you-go overage at $0.003/transaction
  • Team$500/month
    • 25 users
    • 100k+ monthly requests
    • Webhooks
  • Enterprise$undefined/mo
    • Custom limits
    • Role-based access controls
    • HIPAA with BAA

Which should you pick?

Choose Neptune.ai if

  • You need experiment tracking.
  • You want to start without paying.
  • You work on Web, Self-hosted.
  • You also want model registry.
Neptune.ai review

Choose PromptLayer if

  • You need visual prompt management.
  • You want to start without paying.
  • You work on web, api.
  • You also want agent observability.
PromptLayer review

Questions people ask

Is Neptune.ai or PromptLayer better?
Neither clearly leads. Neptune.ai starts at Free and PromptLayer at Free, and user ratings are close enough to be indistinguishable. Choose on capability and platform support.
Which is cheaper, Neptune.ai or PromptLayer?
Neptune.ai starts at Free and PromptLayer at Free.
Does Neptune.ai or PromptLayer run on more platforms?
Neptune.ai runs on Web, Self-hosted. PromptLayer runs on web, api.
Can I use Neptune.ai for free?
Both have a free tier, so you can try either at no cost before committing.
What is Neptune.ai best used for?
Neptune.ai is most often used for machine learning, data analysis, model training, predictive analytics. Of those, machine learning and data analysis are not what PromptLayer is typically brought in for.
What can Neptune.ai do that PromptLayer cannot?
Neptune.ai covers Experiment tracking, Model registry, Metadata logging, Comparison views. PromptLayer covers Visual prompt management, Agent observability, Evaluations, Version control.

Answered from the vendors’ own pages

Neptune.ai: Does Neptune.ai support self-hosting?

Yes. Neptune can be self-hosted on a Kubernetes cluster with ClickHouse, MySQL, and Redis dependencies, allowing organizations to maintain full data control.

Source
PromptLayer: What does PromptLayer cost?

PromptLayer has a free plan, a Pro plan at $49/month, a Team plan at $500/month, and custom Enterprise pricing, with additional usage billed per transaction beyond plan limits.

Source
Neptune.ai: What machine learning frameworks does Neptune integrate with?

Neptune integrates with PyTorch, TensorFlow, Keras, scikit-learn, XGBoost, LightGBM, Hugging Face Transformers, and Optuna for hyperparameter optimization.

Source
PromptLayer: Is there a free plan, and what are its limits?

The Free plan includes 5 users, 2,500 requests per month, 1 workspace, 250 monthly eval cell executions, and datasets up to 10MB.

Source
Neptune.ai: What is the cost for a team of 10 data scientists?

Neptune's Team plan costs $49 per user per month, resulting in $490/month for 10 users, comparable to Weights and Biases at $50/user.

Source
PromptLayer: How is usage metered beyond the plan limits?

Additional usage is charged per transaction for requests, agent runs, and evaluation cell runs, at $0.003/transaction on Pro and $0.002/transaction on Team.

Source
Neptune.ai: When is Neptune.ai shutting down?

Neptune.ai is shutting down its external SaaS service on March 5, 2026, following its acquisition by OpenAI in December 2025. Customers must export and migrate data before that date.

Source
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