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

# Blank comparison rows due to mismatched inputs

export const plans_0 = "Any"

export const deployments_0 = "Braintrust-hosted, Self-hosted"

export const data_plane_version_0 = undefined

export const use_case_0 = "Use case - Experiment comparison with mismatched inputs or custom data structures"

<Note>
  **Applies to:**

  * Plan - {plans_0}
  * Deployment - {deployments_0}
  * {data_plane_version_0}
  * {use_case_0}
</Note>

## Summary

**Issue:** Comparison rows appear blank when comparing two experiments, and the comparison table shows "–" instead of score values for the second experiment.

**Cause:** Experiments are compared based on a comparison key (defaults to `input`), and blank rows indicate the input values don't match exactly between the two experiments.

**Resolution:** Ensure input values match exactly across experiments, or configure a custom comparison key in project settings.

## Resolution Steps

### If input values differ between experiments

#### Step 1: Verify input matching

Check that the `input` field values are identical across both experiments being compared.

#### Step 2: Standardize inputs

Re-run experiments with consistent input values to enable row-by-row comparison.

### Otherwise, if you need to compare on a different field

#### Step 1: Configure comparison key

Navigate to Project Settings and set a custom comparison key under the comparison settings section.

#### Step 2: Select appropriate field

Choose a field that consistently exists and matches across both experiments (e.g., `id`, `metadata.key`, or custom field).

## Additional Information

### Understanding comparison behavior

The comparison table matches rows based on the comparison key. When no match exists, the cell displays "–" in the main table view.

### Checking for matches

Drill into individual traces to see the message "There are no input matches in the comparison experiment" when a row has no corresponding match.

### Best practices

* Use consistent input formatting across experiment runs
* Configure comparison keys before running large experiment sets
* Test comparison configuration with small experiments first