> ## Documentation Index
> Fetch the complete documentation index at: https://docs.langchain.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Log user feedback using the SDK

LangSmith makes it easy to attach [feedback](/langsmith/observability-concepts#feedback) to [traces](/langsmith/observability-concepts#traces). This feedback can come from users, annotators, automated evaluators, and so on, which is crucial for monitoring and evaluating applications.

This page details how to log feedback using the [SDK](/langsmith/reference). For the structure of feedback objects, refer to [Feedback data format](/langsmith/feedback-data-format).

## Use `create_feedback()` / `createFeedback`

<Info>
  **Child runs**
  You can attach user feedback to **any** child run of a trace, not just the trace (root run) itself.
  This is useful for critiquing specific steps of the LLM application, such as the retrieval step or generation step of a RAG pipeline.
</Info>

<Tip>
  **Non-blocking creation (Python only)**
  The Python client will automatically background feedback creation if you pass `trace_id=` to [`create_feedback()`](https://reference.langchain.com/python/langsmith/client/Client/create_feedback).
  This is essential for low-latency environments, where you want to make sure your application isn't blocked on feedback creation.
</Tip>

The following example creates a trace with two child runs, then logs feedback against the root run and against one of the child runs. The TypeScript snippet shows the equivalent `createFeedback` call shape, assuming a `runId` is already available from your application.

<CodeGroup>
  ```python Python theme={"theme":{"light":"catppuccin-latte","dark":"catppuccin-mocha"}}
  from langsmith import Client, trace, traceable

  @traceable
  def foo(x):
      return {"y": x * 2}

  @traceable
  def bar(y):
      return {"z": y - 1}

  client = Client()

  inputs = {"x": 1}
  with trace(name="foobar", inputs=inputs) as root_run:
      result = foo(**inputs)
      result = bar(**result)
      root_run.outputs = result
      trace_id = root_run.id
      child_runs = root_run.child_runs

  # Provide feedback for a trace (a.k.a. a root run)
  client.create_feedback(
      key="user_feedback",
      score=1,
      trace_id=trace_id,
      comment="the user said that ..."
  )

  # Provide feedback for a child run
  foo_run_id = [run for run in child_runs if run.name == "foo"][0].id
  client.create_feedback(
      key="correctness",
      score=0,
      run_id=foo_run_id,
      # trace_id= is optional but recommended to enable batched and backgrounded
      # feedback ingestion.
      trace_id=trace_id,
  )
  ```

  ```typescript TypeScript theme={"theme":{"light":"catppuccin-latte","dark":"catppuccin-mocha"}}
  import { Client } from "langsmith";
  const client = new Client();

      // ... Run your application and get the run_id...
      // This information can be the result of a user-facing feedback form

  await client.createFeedback(
      runId,
      "feedback-key",
      {
          score: 1.0,
          comment: "comment",
      }
  );
  ```
</CodeGroup>

You can even log feedback for in-progress runs using [`create_feedback()`](https://reference.langchain.com/python/langsmith/client/Client/create_feedback) / [`createFeedback`](https://reference.langchain.com/javascript/classes/langsmith.client.Client.html#createfeedback). See [Access the current run (span) within a traced function](/langsmith/access-current-span) for how to get the run ID of an in-progress run.

## Collect feedback from client-side applications

If you need to collect feedback from a browser or other client-side environment without exposing your API key, use **presigned feedback tokens**. These generate a URL scoped to a specific run and feedback key that clients can call directly.

See [Collect feedback with presigned URLs](/langsmith/presigned-feedback-tokens) for the full guide.

To learn more about how to filter traces based on various attributes, including user feedback, see [Filter traces](/langsmith/filter-traces-in-application).

***

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