QnA Maker knowledge base limits and boundaries

QnA Maker limits provided below are a combination of the Azure Cognitive Search pricing tier limits and the QnA Maker pricing tier limits. You need to know both sets of limits to understand how many knowledge bases you can create per resource and how large each knowledge base can grow.

Knowledge bases

The maximum number of knowledge bases is based on Azure Cognitive Search tier limits.

Azure Cognitive Search tier Free Basic S1 S2 S3 S3 HD
Maximum number of published knowledge bases allowed 2 14 49 199 199 2,999

For example, if your tier has 15 allowed indexes, you can publish 14 knowledge bases (1 index per published knowledge base). The fifteenth index, testkb, is used for all the knowledge bases for authoring and testing.

Extraction Limits

File naming constraints

File names may not include the following characters:

Do not use character
Single quote '
Double quote "

Maximum file size

Format Max file size (MB)
.docx 10
.pdf 25
.tsv 10
.txt 10
.xlsx 3

Maximum number of files

The maximum number of files that can be extracted and maximum file size is based on your QnA Maker pricing tier limits.

Note

Custom question answering (preview) is a free service with no limits on the number of sources that can be added. Throughput is currently capped at 10 transactions per second for both management APIs and prediction APIs.

The maximum number of deep-links that can be crawled for extraction of QnAs from a URL page is 20.

Metadata Limits

Metadata is presented as a text-based key:value pair, such as product:windows 10. It is stored and compared in lower case. Maximum number of metadata fields is based on your Azure Cognitive Search tier limits.

For GA version, since the test index is shared across all the KBs, the limit is applied across all KBs in the QnA Maker service.

Azure Cognitive Search tier Free Basic S1 S2 S3 S3 HD
Maximum metadata fields per QnA Maker service (across all KBs) 1,000 100* 1,000 1,000 1,000 1,000

By name and value

The length and acceptable characters for metadata name and value are listed in the following table.

Item Allowed chars Regex pattern match Max chars
Name (key) Allows
alphanumeric (letters and digits)
_ (underscore)
Must not contain spaces.
^[a-zA-Z0-9_]+$ 100
Value Allows everything except
: (colon)
| (vertical pipe)
Only one value allowed.
^[^:|]+$ 500

Knowledge Base content limits

Overall limits on the content in the knowledge base:

  • Length of answer text: 25,000 characters
  • Length of question text: 1,000 characters
  • Length of metadata key text: 100 characters
  • Length of metadata value text: 500 characters
  • Supported characters for metadata name: Alphabets, digits and _
  • Supported characters for metadata value: All except : and |
  • Length of file name: 200
  • Supported file formats: ".tsv", ".pdf", ".txt", ".docx", ".xlsx".
  • Maximum number of alternate questions: 300
  • Maximum number of question-answer pairs: Depends on the Azure Cognitive Search tier chosen. A question and answer pair maps to a document on Azure Cognitive Search index.
  • URL/HTML page: 1 million characters

Create Knowledge base call limits:

These represent the limits for each create knowledge base action; that is, clicking Create KB or calling the CreateKnowledgeBase API.

  • Recommended maximum number of alternate questions per answer: 300
  • Maximum number of URLs: 10
  • Maximum number of files: 10
  • Maximum number of QnAs permitted per call: 1000

Update Knowledge base call limits

These represent the limits for each update action; that is, clicking Save and train or calling the UpdateKnowledgeBase API.

  • Length of each source name: 300
  • Recommended maximum number of alternate questions added or deleted: 300
  • Maximum number of metadata fields added or deleted: 10
  • Maximum number of URLs that can be refreshed: 5
  • Maximum number of QnAs permitted per call: 1000

Add unstructured file limits

Note

  • If you need to use larger files than the limit allows, you can break the file into smaller files before sending them to the API.

These represent the limits when unstructured files are used to Create KB or call the CreateKnowledgeBase API:

  • Length of file: We will extract first 32000 characters
  • Maximum 3 responses per file.

Prebuilt question answering limits

Note

  • If you need to use 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.

These represent the limits when Prebuilt API is used to Generate response or call the GenerateAnswer API:

  • Number of documents: 5
  • Maximum size of a single document: 5,120 characters
  • Maximum 3 responses per document.

Important

Support for unstructured file/content and Prebuilt API is available only in Custom question answering (preview)

Next steps

Learn when and how to change service pricing tiers.