Query Data via SDKs
Langfuse is open-source and data tracked with Langfuse is open. You can query data via: SDKs and API. For export functionality, see Export Data.
Common use cases:
- Train or fine-tune models on the production traces in Langfuse. E.g. to create a small model after having used a large model in production for a specific use case.
- Collect few-shot examples to improve quality of output.
- Programmatically create datasets.
If you are new to Langfuse, we recommend familiarizing yourself with the Langfuse data model.
New data is typically available for querying within 15-30 seconds of ingestion, though processing times may vary at times. Please visit status.langfuse.com if you encounter any issues.
SDKs
Via the SDKs for Python and JS/TS you can easily query the API without having to write the HTTP requests yourself.
pip install langfusefrom langfuse import get_client
langfuse = get_client() # uses environment variables to authenticateThe api namespace is auto-generated from the Public API (OpenAPI). Method names mirror REST resources and support filters and pagination.
Traces
traces = langfuse.api.trace.list(limit=100, user_id="user_123", tags=["production"]) # pagination via cursor
trace = langfuse.api.trace.get("traceId")Observations
observations = langfuse.api.observations.get_many(trace_id="abcdef1234", type="GENERATION", limit=100)
observation = langfuse.api.observations.get("observationId")Sessions
sessions = langfuse.api.sessions.list(limit=50)Scores
langfuse.api.score_v_2.get(score_ids = "ScoreId")Prompts
Please refer to the prompt management documentation on fetching prompts.
Datasets
# Namespaces:
# - langfuse.api.datasets.*
# - langfuse.api.dataset_items.*
# - langfuse.api.dataset_run_items.*Metrics
query = """
{
"view": "traces",
"metrics": [{"measure": "count", "aggregation": "count"}],
"dimensions": [{"field": "name"}],
"filters": [],
"fromTimestamp": "2025-05-01T00:00:00Z",
"toTimestamp": "2025-05-13T00:00:00Z"
}
"""
langfuse.api.metrics.metrics(query = query)Async equivalents
# All endpoints are also available as async under `async_api`:
trace = await langfuse.async_api.trace.get("traceId")
traces = await langfuse.async_api.trace.list(limit=100)Common filtering & pagination
- limit, cursor (pagination)
- time range filters (e.g., start_time, end_time)
- entity filters: user_id, session_id, trace_id, type, name, tags, level, etc.
See the Public API for the exact parameters per resource.