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Azure AI Content Understanding service quotas and limits

This article offers a quick reference of the quotas and limits for the Azure AI Content Understanding service.

Resource limits

Quota Standard (S0)
Max analyzers 100k
Max classifiers 100k
Max person directories 100k
Max analysis/min 1000 pages/images
Four hours of audio
Four hours of video
Max operations/min 3000

General limits

Property Limit
Resource IDs 1-64 characters ([a-zA-Z0-9._-]{1,64})
URL properties ≤ 8,192 characters
Description properties ≤ 1,024 characters
Field names ≤ 64 characters ([\p{L}\p{Nl}\p{Mn}\p{Mc}\p{Nd}\p{Pc}._-]{1,64})
Tags properties ≤ 10 tags
Tag key ≤ 64 characters ([a-zA-Z0-9+-.:=_/]{1,64})
Tag value ≤ 256 characters ([a-zA-Z0-9+-.:=_/]{0,256})
Image reference ID ≤ 256 characters

Analyzers

Input file limits

Document and text

Supported File Types File Size Length
✓ .pdf
✓ .tiff
✓ .jpg, .png, .bmp, .heif		 ≤ 200 MB ≤ 300 pages
✓ .docx, .xlsx, .pptx ≤ 200 MB ≤ 1M characters
✓ .txt
✓ .html, .md, .rtf
✓ .eml, .msg
✓ .xml		 ≤ 1 MB ≤ 1M characters

Note

Pro mode currently only supports .pdf, .tiff, and image file types as input. Total input may not exceed 100 MB and 150 pages.

Image

Supported File Types File Size Resolution
✓ .jpg, .png, .bmp, .heif ≤ 200 MB Min: 50 x 50 pixels
Max: 10k x 10k pixels

Audio

Supported File Types File Size Length
✓ .wav (PCM, A-law, μ-law)
✓ .mp3
✓ .mp4
✓ .opus, .ogg (Opus)
✓ .flac
✓ .wma
✓ .aac
✓ .amr (AMR-NB, AMR-WB)
✓ .3gp (AMR-NB, AMR-WB)
✓ .webm (Opus, Vorbis)
✓ .m4a (AAC, ALAC)
✓ .spx		 ≤ 1 GB† ≤ 4 hours†

† For files ≤ 300 MB or ≤ 2 hours, Content Understanding transcription time is substantially reduced.

Video

Supported File Types File Size Resolution Length
✓ .mp4, .m4v
✓ .flv (H.264 and AAC)
✓ .wmv, .asf
✓ .avi
✓ .mkv
✓ .mov		 ≤20 GB † Min: 320 x 240 pixels
Max: 1920 x 1,080 pixels		 ≤4 hours †

Note

Video analysis has the following limitations:

  • Direct upload: Maximum file size of 200 MB and maximum duration of 30 minutes when uploading video directly
  • Frame sampling: Analyzes approximately one frame per second, which may miss quick movements or brief events
  • Resolution: All frames are scaled to 512 x 512 pixels, which may affect visibility of small details or distant objects

Field schema limits

Content Understanding supports both basic field value types and nested structures, including lists, groups, tables, and fixed tables.

  • Basic field value types: string, date, time, number, integer, and boolean.
  • List field: A sequence of values of the same type, represented as an array of basic fields in the API.
  • Group field: A set of semantically related fields, represented as an object of basic fields in the API.
  • Table field: A variable number of items with fixed subfields, represented as an array of objects of basic fields in the API.
  • Fixed table field: A group of fields with shared subfields, represented as an object of objects of basic fields in the API.

Basic limits

Property Document Text Image Audio Video
Max fields 100 100 100 100 100
Max classify field categories 300 300 300 300 300
Supported generation methods extract
generate
classify		 generate
classify		 generate
classify		 generate
classify		 generate
classify
  • The Max fields limit includes all named fields. For example, a list of strings counts as one field, while a group with string and number subfields counts as three fields.
  • The Max classify field categories limit is the total number of categories across all fields using the classify generation method.

Knowledge source limits

Type Limits
Training data Documents only
1 GB total
50k pages/images total
Reference data Documents only
100 MB total
5k pages total

Classifier

General limits

Note

This limit is for Content Understanding classifier itself, not classify fields within the extraction capability.

Property Limit
Category name Can't start with a dollar sign ($)
Category name and description Maximum 120 characters for combined name and description in each category
Number of categories 1 to 50 per classifier

Input file limits

Supported File Types File Size Length
✓ .pdf
✓ .tiff
✓ .jpg, .png, .bmp, .heif		 ≤ 200 MB ≤ 300 pages
✓ .txt ≤ 1 MB ≤ 1M characters

Face / Person Directories

General limits

Property Value
Max faces per person directory 1,000,000
Max persons per person directory 1,000,000
Max detected faces per image 100
Max identified person candidates per search 10
Max similar faces returned per search 1000

Input file limits

Supported File Types File Size Length
✓ .jpg, .png, .bmp, .webp, .gif, .ico ≤ 200 MB Max: 15k x 15k pixels