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

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.

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

Metadata Limits

By Azure Cognitive Search pricing tier

Maximum number of metadata fields per knowledge base is based on your Azure Cognitive Search tier limits.

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 Allows
alphanumeric (letters and digits)
_ (underscore)
^[a-zA-Z0-9_]+$ 100
Value Allows everything except
: (colon)
| (vertical pipe)
^[^:|]+$ 500

Knowledge Base content limits

Overall limits on the content in the knowledge base:

  • Length of answer text: 25,000
  • Length of question text: 1,000
  • Length of metadata key/value text: 100
  • 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.

  • Maximum number of alternate questions per answer: 300
  • Maximum number of URLs: 10
  • Maximum number of files: 10

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
  • 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

Next steps

Learn when and how to change service pricing tiers.