# Overview

The Forced Alignment API provides improved accuracy for per-word timestamps for a transcript.

## API endpoint

The base URL for this version of the API is `https://api.rev.ai/alignment/v1/`. All endpoints described in this documentation are relative to this base URL.

## Authentication

Clients must authenticate by including their [Rev AI access token](/api/security#access-token) as a query parameter in their requests. If the access token is invalid or the query parameter is not present, a `401` error code will be returned.

## Turnaround time

Turnaround time increases with the length of the input audio file.

The maximum possible turnaround time for a job is 3 hours. Jobs which exceed this time limit will be automatically marked as failed.

The following table illustrates average turnaround times for different audio lengths:

| Audio length | Average turnaround time (seconds) |
|  --- | --- |
| 1 minute | 9.8 seconds |
| 2 minutes | 13.7 seconds |
| 5 minutes | 24.6 seconds |
| 10 minutes | 35 seconds |
| 30 minutes | 100 seconds |
| 60 minutes | 450 seconds |
| 2 hours | 670 seconds |