18.4
Opik helps teams building applications or agents that call an LLM log actions and evaluate behavior through development, testing, and production.
Free planOpen sourceWebAPILinux
Best LLM Developer Tools in 2026
LLM developer tools let you create applications using large language models, link them with providers, assess results and monitor runtime activity. This list includes API, web and self-hosted offerings alongside software for Linux, macOS and Windows. Use deployment methods, available LLM providers, evaluation and observability capabilities, SDK languages, open-source availability and pricing to compare them.
28.3
DeepEval is a free, open-source framework for creating evaluation pipelines that test AI systems.
Free planOpen sourceWebAPILinux
38.2
Langfuse is an open-source AI engineering platform for teams debugging, analyzing, and iterating on AI agent applications.
Free planOpen sourceWebAPILinux
- 4
LangSmith
LangSmith is a platform for building, evaluating, deploying, monitoring, and improving AI agents.
Free planWebAPILinuxmacOS8.0$39 usage-based - 5
Promptfoo
Promptfoo helps developers and enterprises evaluate prompts and test AI applications for security risks.
Free planOpen sourceWebAPILinuxmacOS7.8Free plan - 6
Braintrust
Braintrust is an observability platform for teams improving AI agents that run in production.
Free planWebAPISelf-hosted7.7From $249 a month - 7
LlamaIndex
LlamaIndex helps developers and enterprises process documents and build AI workflows around them.
Free planWebAPILinuxSelf-hosted7.1From $50 a month - 8
PromptLayer
PromptLayer is a platform for teams that build and improve AI products.
Free planWebAPISelf-hosted7.0From $49 a month - 9
Helicone
Helicone is a platform for routing, debugging, and analyzing AI applications.
Free planWebAPISelf-hosted6.9From $79 a month - 10
LangChain
LangChain is a free, open-source framework for building agents that connect models with tools.
Free planAPISelf-hosted6.8$39 usage-based - 11
Portkey
Portkey is a platform for managing, observing, and governing generative AI across teams.
Free planWebAPISelf-hosted6.8From $49 a month - 12
CrewAI AMP
Free planWebAPISelf-hosted6.4Free plan - 13
Haystack
Haystack is an open-source AI orchestration framework for developers building agents, multimodal applications, advanced retrieval-augmented…
Free planAPISelf-hosted6.4Free plan - 14
OpenRouter
OpenRouter provides access to hundreds of AI models through a single API endpoint.
Free planWebAPI6.4Free plan - 15
Arize Phoenix
Arize Phoenix helps teams trace, evaluate, debug, and improve AI applications.
Free planWebAPISelf-hosted6.3Free plan - 16
Replicate
Free planWebAPI6.3Free plan - 17
LiteLLM
Free planWebAPISelf-hosted6.2Free plan - 18
6.0From $0.06 a month - 19
DSPy
DSPy is a free, MIT-licensed, open-source Python framework for building AI programs and systems.
APISelf-hosted5.7 - 20
Fireworks AI
WebAPISelf-hosted5.7 - 21
Ragas
Ragas is a free, self-hosted library for systematically evaluating large language model applications.
APILinuxSelf-hosted5.7 - 22
Cohere North
WebSelf-hosted5.5 - 23
AutoGen
LinuxmacOSWindows4.9 - 24
GroqCloud
Web4.8 - 254.7
Choosing well
Choose a deployment model
Determine whether each tool is accessed by API, through a browser-based interface or from a self-hosted installation. Linux, macOS and Windows availability may be important for local development or deciding where the software operates.
Cohere North offers self-hosted and web platforms; Fireworks AI offers API, self-hosted and web deployment.
Check the free and paid terms
A free plan can help you start without a paid commitment. Read the pricing note for limits and the point where paid use begins.
Braintrust shows a free plan, with paid service starting at $249 per month. Helicone shows a free plan, paid service from $79 per month and a 7-day trial.
Match your LLM providers
Review the provider connections before choosing a tool. This affects which models and services your application can use through the tool.
Assess evaluation and observability
Evaluation measures the outputs produced by a model or application. Observability lets you examine software behaviour during operation. Compare the coverage listed for both areas rather than assuming they are included.
Review SDK languages and source access
Check the SDK languages that fit your codebase. Before reading or modifying implementation code, confirm its open-source status and licence.
DSPy and Haystack show open-source pricing notes; Google Gemini API and AutoGen show free plans.
Questions people ask
Is there a free plan to begin with?
Tools including Arize Phoenix, AutoGen, Braintrust, CrewAI AMP, DeepEval, DSPy, Google Gemini API, GroqCloud, Haystack and Helicone list free plans.
What deployment methods are represented?
API, web and self-hosted deployment appear in the category, along with Linux, macOS and Windows platforms.
Does the list contain open-source options?
Yes. Open-source code is one comparison field, and DSPy and Haystack show open-source pricing notes.
Do any tools offer free trials?
Free-trial availability is compared; Helicone's pricing note includes a 7-day trial.