> For the complete documentation index, see [llms.txt](https://raia-software-inc.gitbook.io/tacview/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://raia-software-inc.gitbook.io/tacview/technical-documentation/flight-recording-authentication.md).

# Flight Recording Authentication

Tacview can help determine whether an `ACMI` file is authentic, or whether it has been modified after it was recorded.

`ACMI` files recorded by the official Tacview data recorders, including the recorders for DCS World, X-Plane, and Microsoft Flight Simulator, include a validation hash inside the file. Tacview uses this hash to detect whether the file has been modified since the original recording.

This feature is especially useful for validating flights used in competitions, virtual squadron events, training logs, or any situation where the integrity of a flight recording matters.

The authentication hash is not cryptographic. A determined professional could still bypass it. However, it is enough to detect accidental modifications and discourage normal manual tampering.

When you open an authenticated `ACMI` file in Tacview, a message is displayed for several seconds at the top of the 3D view. This message indicates whether the file appears authentic or whether it has been modified.

![This File is Authentic](/files/MZl4RtTJDHpz1IremLJC)

#### Command Line Authentication

You can also authenticate an ACMI file from the command line. This is useful when you need to automate validation for competitions, servers, or custom tools.

```
/Quiet /Open:"C:\Users\...\Documents\Tacview\Tacview-20250324-DCS-cold-equation.txt.acmi" /Authenticate
```

This command runs Tacview in the background, without displaying the user interface, and checks the specified file.

The command returns the following result code:

| Return Value      | Meaning                                                                      |
| ----------------- | ---------------------------------------------------------------------------- |
| `-1`              | The file is authentic.                                                       |
| `0`               | The file has been modified.                                                  |
| `Any other value` | An error occurred, such as a missing file or invalid command line parameter. |

If an error occurs, check the [Tacview log](/tacview/faq/technical-issues-faq-2.md#tacview-log) for more details.