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.


Clients must authenticate by including their Rev AI 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