---
title: '📱 App types'
---

## App Types

We have three types of App.

### App

```python
from embedchain import App
app = App()
```

- `App` uses OpenAI's model, so these are paid models. 💸 You will be charged for embedding model usage and LLM usage.
- `App` uses OpenAI's embedding model to create embeddings for chunks and ChatGPT API as LLM to get answer given the relevant docs. Make sure that you have an OpenAI account and an API key. If you have don't have an API key, you can create one by visiting [this link](https://platform.openai.com/account/api-keys).
- `App` is opinionated. It uses the best embedding model and LLM on the market.
- Once you have the API key, set it in an environment variable called `OPENAI_API_KEY`

```python
import os
os.environ["OPENAI_API_KEY"] = "sk-xxxx"
```

### OpenSourceApp

```python
from embedchain import OpenSourceApp
app = OpenSourceApp()
```

- `OpenSourceApp` uses open source embedding and LLM model. It uses `all-MiniLM-L6-v2` from Sentence Transformers library as the embedding model and `gpt4all` as the LLM.
- Here there is no need to setup any api keys. You just need to install embedchain package and these will get automatically installed. 📦
- Once you have imported and instantiated the app, every functionality from here onwards is the same for either type of app. 📚
- `OpenSourceApp` is opinionated. It uses the best open source embedding model and LLM on the market.

### CustomApp

```python
from embedchain import CustomApp
from embedchain.config import CustomAppConfig
from embedchain.models import Providers, EmbeddingFunctions

config = CustomAppConfig(embedding_fn=EmbeddingFunctions.OPENAI, provider=Providers.OPENAI)
app = CustomApp()
```

- `CustomApp` is not opinionated.
- Configuration required. It's for advanced users who want to mix and match different embedding models and LLMs. Configuration required.
- while it's doing that, it's still providing abstractions through `Providers`.
- paid and free/open source providers included.
- Once you have imported and instantiated the app, every functionality from here onwards is the same for either type of app. 📚


### PersonApp

```python
from embedchain import PersonApp
naval_chat_bot = PersonApp("name_of_person_or_character") #Like "Yoda"
```

- `PersonApp` uses OpenAI's model, so these are paid models. 💸 You will be charged for embedding model usage and LLM usage.
- `PersonApp` uses OpenAI's embedding model to create embeddings for chunks and ChatGPT API as LLM to get answer given the relevant docs. Make sure that you have an OpenAI account and an API key. If you have don't have an API key, you can create one by visiting [this link](https://platform.openai.com/account/api-keys).
- Once you have the API key, set it in an environment variable called `OPENAI_API_KEY`

```python
import os
os.environ["OPENAI_API_KEY"] = "sk-xxxx"
```

#### Compatibility with other apps

- If there is any other app instance in your script or app, you can change the import as

```python
from embedchain import App as EmbedChainApp
from embedchain import OpenSourceApp as EmbedChainOSApp
from embedchain import PersonApp as EmbedChainPersonApp

# or

from embedchain import App as ECApp
from embedchain import OpenSourceApp as ECOSApp
from embedchain import PersonApp as ECPApp
```
