API

Neuronpedia has a public API for almost everything on the website. You can get features and explanations, test activations, steer, search, make graphs, run the Jacobian Lens, use NLAs, and upload data.

API reference: https://neuronpedia.org/api-doc. You can test calls in your browser.

Before You Start

• Check what is available. The Available Resources page lists all models and sources in the API. Only sources with inference enabled can do steering, test activations, and search via inference.
• Get an API key. Many GET endpoints work without a key. Endpoints that write data need a key in the x-api-key header. See Accounts.
• Know the limits. See Rate Limits.
• Use exports for bulk data. If you need data for many features, download the exports. Do not call the API for each feature.

Example - Get a Feature

Add /api/feature after neuronpedia.org in any feature URL:

curl https://www.neuronpedia.org/api/feature/gemma-2-2b/20-gemmascope-res-16k/10956

The response has the feature's activations, explanations, logits, and density.

Example - Test Activations

Get one feature's activations for your text:

curl -X POST https://www.neuronpedia.org/api/activation/new \
  -H "Content-Type: application/json" \
  -d '{
    "feature": {"modelId": "gemma-2-2b", "source": "20-gemmascope-res-16k", "index": "10956"},
    "customText": "We are committed to being your best vendor."
  }'

Groups of Endpoints

Group	What it does
Features	Get a feature or vector.
Activations	Test one feature, or all features in a source, with your text.
Explanations	Search, make, and score explanations. Test the interpretable score.
Search via Inference / Search TopK by Token	Find the top features for your text.
Steering	Steer completions and chats. See Steering.
Attribution Graphs	Make, upload, get, and steer graphs. Save subgraphs. See Circuit Tracing.
Jacobian Lens	Run prompts through the J-lens.
NLA	Explain activations with NLAs.
Vectors	Upload, list, and delete custom vectors.
Lists and Bookmarks	Make and change lists and bookmarks.
Models	Add a new model.

Python and TypeScript

• Python - Use the Neuronpedia Python library (pip install neuronpedia).
• Other languages - The API reference shows example code for Shell, Python, Node.js, Ruby, and more.

Questions or Requests

Do you need a new endpoint, or a higher limit? Contact us.