LlamaIndex vs Semantic Kernel
Which should you use? A side-by-side look at what each one does, who it suits, what it costs, how hard it is to set up, and where each falls short.
Open source · MIT
Python framework for building LLM apps that query your own documents and data.
Open source · MIT
Open-source SDK for building AI agents and multi-agent apps in Python, .NET and Java.
The short answer
Choose LlamaIndex if you need…
- Python developers building retrieval-augmented generation (RAG) apps over private documents
- Teams wanting a modular toolkit where they can swap LLM, embedding and vector store providers
- Developers building agent workflows that query their own data
- Beginners who want a short path to a working document question-answering prototype
Choose Semantic Kernel if you need…
- Developers already using Azure OpenAI or OpenAI who want a structured SDK for agents
- Teams working in .NET, Python or Java who want one framework across languages
- Projects that need plugins built from native code, prompt templates, OpenAPI specs or MCP
- Existing Semantic Kernel users maintaining or migrating older code
Side-by-side
| LlamaIndex | Semantic Kernel | |
|---|---|---|
| Type | Library | Library |
| Price | Free and open source | Free and open source |
| Licence | MIT | MIT |
| GitHub stars | 52.8k | 28.7k |
| Setup difficulty | Intermediate | Intermediate |
| How you get it | Install with a package manager | Install with a package manager |
| Main language | Python | C# |
| Last code update | 10 days ago | 4 days ago |
What each one is
LlamaIndex
LlamaIndex is an open-source Python framework for connecting large language models to your own data, such as PDFs, documents, APIs and SQL databases. It provides connectors to load data, ways to structure it into indexes, and retrieval tools that feed relevant context to an LLM. The README also notes that the company's main focus has shifted toward its commercial LlamaParse document platform, with the open-source framework still available.
Semantic Kernel
Semantic Kernel is a model-agnostic SDK from Microsoft that lets developers connect large language models (such as OpenAI or Azure OpenAI models) to their own apps, add tools and plugins, and orchestrate one or more AI agents. The README says it is now succeeded by Microsoft Agent Framework, so new projects should check that project first.
Best for
LlamaIndex
- Python developers building retrieval-augmented generation (RAG) apps over private documents
- Teams wanting a modular toolkit where they can swap LLM, embedding and vector store providers
- Developers building agent workflows that query their own data
- Beginners who want a short path to a working document question-answering prototype
Semantic Kernel
- Developers already using Azure OpenAI or OpenAI who want a structured SDK for agents
- Teams working in .NET, Python or Java who want one framework across languages
- Projects that need plugins built from native code, prompt templates, OpenAPI specs or MCP
- Existing Semantic Kernel users maintaining or migrating older code
Strengths
LlamaIndex
- Large ecosystem of over 300 integration packages, per the README
- Modular design lets you customize or replace components like retrievers and query engines
- Offers both a high-level API for quick starts and lower-level APIs for advanced control
Semantic Kernel
- Supports several models and providers, including OpenAI, Azure OpenAI, Hugging Face and NVidia, per the README
- Offers examples in Python and C# with matching quickstarts
- Permissive MIT license and a large public project with about 28,700 stars
Not ideal for
LlamaIndex
- Non-programmers, since it is a Python library that requires writing code
- Projects that need a fully managed hosted service, because the README points to LlamaParse for the hosted offering and the framework is a toolkit you run yourself
- Users who only need simple one-off document parsing, where a standalone parser may be simpler
Semantic Kernel
- Non-programmers: it is a developer SDK and needs code to use, so no-code users should look elsewhere
- Teams starting fresh who want the newest path: the README directs users to Microsoft Agent Framework as the successor
- Simple scripts that only need one direct API call, where an SDK adds more structure than needed
Trade-offs
LlamaIndex
- The README says the company's primary focus has shifted to LlamaParse, so the open-source framework is secondary to its commercial product
- The README is not updated as often as the documentation, so you should check the docs for current details
- Many separate integration packages means you must choose and install the ones you need
Semantic Kernel
- The README states the project is succeeded by Microsoft Agent Framework, so long-term direction may point elsewhere
- Quickstarts assume Azure or OpenAI credentials and a configured environment, so setup needs some engineering work
- Java support is pointed to a separate build guide rather than documented here
Getting started
LlamaIndex
Install core and selected integrations
pip install llama-index-coreAdd an LLM integration
pip install llama-index-llms-openaiSemantic Kernel
Set Azure OpenAI API key
export AZURE_OPENAI_API_KEY=AAA....Set OpenAI API key (alternative)
export OPENAI_API_KEY=sk-...Frequently asked questions
What is the difference between LlamaIndex and Semantic Kernel?
LlamaIndex: Python framework for building LLM apps that query your own documents and data. Semantic Kernel: Open-source SDK for building AI agents and multi-agent apps in Python, .NET and Java. LlamaIndex suits python developers building retrieval-augmented generation (rag) apps over private documents, while Semantic Kernel suits developers already using azure openai or openai who want a structured sdk for agents.
Are LlamaIndex and Semantic Kernel free?
LlamaIndex: Free and open source. Semantic Kernel: Free and open source.
Is LlamaIndex or Semantic Kernel more popular?
LlamaIndex has more GitHub stars (52.8k) than Semantic Kernel (28.7k). Popularity isn't the same as fit — check which one matches your use case above.
What are other alternatives to LlamaIndex and Semantic Kernel?
Other options people compare them with include LangChain, LangGraph, PageIndex, OpenAI Agents SDK, LightRAG.
Keep comparing
Built from our catalogue entries for both products: open-source details come from each project's README (AI-assisted, refreshed weekly) and GitHub data; AI-tool details are editorial. Spotted something wrong? Let us know from either product's page.