Service limits for Azure Cognitive Service for Language


This article only describes the limits for pre-configured features in Azure Cognitive Service for Language: To see the service limits for customizable features, see the following articles:

Use this article to find the limits for the size, and rates that you can send data to the following features of the language service.

When using features of the Language service, keep the following in mind:

  • Pricing is not affected by data or rate limits. Pricing is based on the number of text records you send to the API, and is subject to your Language resource's pricing details.
    • A text record is measured as 1000 characters.
  • Data and rate limits are based on the number of documents you send to the API. If you need to analyze larger documents than the limit allows, you can break the text into smaller chunks of text before sending them to the API.
  • A document is a single string of text characters.

Maximum characters per document

The following limit specifies the maximum number of characters that can be in a single document.

Feature Value
Conversation issue and resolution summarization 40,000 characters as measured by StringInfo.LengthInTextElements.
Text Analytics for health 125,000 characters as measured by StringInfo.LengthInTextElements.
All other pre-configured features (synchronous) 5,120 as measured by StringInfo.LengthInTextElements. If you need to submit larger documents, consider using the feature asynchronously (described below).
All other pre-configured features (asynchronous) 125,000 characters across all submitted documents, as measured by StringInfo.LengthInTextElements (maximum of 25 documents).

If a document exceeds the character limit, the API will behave differently depending on how you're sending requests.

If you're sending requests synchronously:

  • The API won't process a document that exceeds the maximum size, and will return an invalid document error for it. If an API request has multiple documents, the API will continue processing them if they are within the character limit.

If you're sending requests asynchronously:

  • The API will reject the entire request and return a 400 bad request error if any document within it exceeds the maximum size.

Maximum request size

The following limit specifies the maximum size of documents contained in the entire request.

Feature Value
All pre-configured features 1MB

Maximum documents per request

Exceeding the following document limits will generate an HTTP 400 error code.


When sending asynchronous API requests, you can send a maximum of 25 documents per request.

Feature Max Documents Per Request
Conversation summarization 1
Language Detection 1000
Sentiment Analysis 10
Opinion Mining 10
Key Phrase Extraction 10
Named Entity Recognition (NER) 5
Personally Identifying Information (PII) detection 5
Document summarization 25
Entity Linking 5
Text Analytics for health 25 for the web-based API, 1000 for the container. (125,000 characters in total)

Rate limits

Your rate limit will vary with your pricing tier. These limits are the same for both versions of the API. These rate limits don't apply to the Text Analytics for health container, which does not have a set rate limit.

Tier Requests per second Requests per minute
S / Multi-service 1000 1000
S0 / F0 100 300

Requests rates are measured for each feature separately. You can send the maximum number of requests for your pricing tier to each feature, at the same time. For example, if you're in the S tier and send 1000 requests at once, you wouldn't be able to send another request for 59 seconds.

See also