The Language Identification API provides additional speech insights by identifying the spoken language in a given transcript.

API endpoint

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


The base URL for this version of the API differs for non-US deployments. Users working with non-US deployments should obtain the correct base URL for their deployment from the Rev AI global deployments page.


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.

Confidence scores

The confidence scores in a result represent how confident our model is that the given language is the language spoken in the submitted audio. This score is always a numeric value in the range [0, 1].

Turnaround time

The average turnaround time ranges from 0.01 to 0.1 second for every 1 second of input audio. This means that, for example, given an input audio file of 30 seconds duration, turnaround time would range from 0.3 seconds to 3 seconds on average.


The maximum possible turnaround time for a job is 2 hours. Jobs which exceed this time limit will be automatically marked as failed.

An important point to note here is that the turnaround time is influenced by two variables: the job overhead (constant) and the audio length (variable). As a quick rule of thumb, the following table illustrates average turnaround times for different audio lengths:

Audio length Average turnaround time (seconds)
1 minute 10.2 seconds
2 minutes 4.8 seconds
5 minutes 7.5 seconds
10 minutes 12 seconds
30 minutes 27 seconds
60 minutes 36 seconds
5 hours 90 seconds

If you require faster turnaround time or assistance with failed jobs, please contact the support team at support@rev.ai.