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

# Get Historical Emission Version History

> Who changed a historical emission entry, when, and which fields

[← Historical Emissions](https://code.dcycle.io/api-reference/historical-emissions/overview.md)

Returns a paginated list of every change made to a historical emission entry: who made it, when, and the
before/after value of each tracked field. The entry can be one of your organization or of a company of its group.

Tracked fields: `organization_id`, `category`, `total_co2e`, `start_date`, `end_date`, `description`, `file_name`.

## Request

### Headers

**x-api-key** `string` *required*

Your API key for authentication

**Example:** `sk_live_1234567890abcdef`

**x-organization-id** `string` *required*

Your organization UUID

**Example:** `a8315ef3-dd50-43f8-b7ce-d839e68d51fa`

### Path Parameters

**historical\_emission\_id** `string` *required*

UUID of the historical emission entry

**Example:** `"a1b2c3d4-e5f6-7890-abcd-ef1234567890"`

### Query Parameters

**page** `integer` (default: 1)

Page number (1-based)

**size** `integer` (default: 50)

Number of version entries per page

## Response

**items** `array`

Version entries, newest first:

| Field | Type | Description |
| - | - | - |
| `transaction_id` | integer | Internal transaction ID |
| `operation_type` | string | `CREATE`, `UPDATE` or `DELETE` |
| `issued_at` | datetime \| null | When the change was committed |
| `user_id` | string \| null | User who made the change (`null` for system changes) |
| `user_first_name` | string \| null | First name of that user |
| `user_last_name` | string \| null | Last name of that user |
| `changes` | array | `{ field, old_value, new_value }` per tracked field that changed |

**total** `integer`

Total number of version entries

**page** `integer`

Current page number

**size** `integer`

Page size

## Example

```bash cURL theme={"theme":{"light":"github-light","dark":"github-dark"}}
curl -X GET "https://api.dcycle.io/v1/historical-emissions/${HISTORICAL_EMISSION_ID}/versions" \
  -H "x-api-key: ${DCYCLE_API_KEY}" \
  -H "x-organization-id: ${DCYCLE_ORG_ID}"
```

### Successful Response

```json theme={"theme":{"light":"github-light","dark":"github-dark"}}
{
  "items": [
    {
      "transaction_id": 1842,
      "operation_type": "UPDATE",
      "issued_at": "2026-10-30T09:12:00Z",
      "user_id": "user-uuid-here",
      "user_first_name": "Ana",
      "user_last_name": "García",
      "changes": [{ "field": "total_co2e", "old_value": 45200.5, "new_value": 46100.0 }]
    }
  ],
  "total": 2,
  "page": 1,
  "size": 50
}
```

## Common Errors

### 401 Unauthorized

**Cause:** Missing or invalid API key

```json theme={"theme":{"light":"github-light","dark":"github-dark"}}
{"detail": "Invalid API key for organization", "code": "INVALID_API_KEY"}
```

### 404 Not Found

**Cause:** Historical emission not found, deleted, or outside your organization and its group

## Related Endpoints

> **[Get](https://code.dcycle.io/api-reference/historical-emissions/get.md)**
>
> View the entry

> **[Update](https://code.dcycle.io/api-reference/historical-emissions/update.md)**
>
> Modify an existing entry


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