specification: API Commons Rate Limits
specificationVersion: '0.1'
schema: https://raw.githubusercontent.com/api-evangelist/interface-research/main/schema/api-commons.yml#/$defs/RateLimits
provider: Bloomberg Applications
providerId: bloomberg-applications
generated: '2026-08-27'
method: searched
source: >-
  https://data.bloomberglp.com/professional/sites/10/2017/03/BLPAPI-Core-Developer-Guide.pdf
  (sections "Request Size Restrictions", 6.7 "Data Limits", 9.2.5 "//BLP/REFDATA")
created: '2026-05-04'
modified: '2026-08-27'
description: >-
  Replaces a 2026-05-04 bulk-sweep scaffold that asserted free/professional/enterprise tiers with
  X-RateLimit-* headers. None of that was Bloomberg's. Bloomberg publishes no HTTP rate-limit
  headers on this surface, because the metered surface is not HTTP: BLPAPI meters consumption in
  unique subscriptions and reference-data hits, and signals exhaustion as typed LIMIT messages on
  the event stream. The structural caps below are published verbatim in Bloomberg's own developer
  guide. The numeric daily/monthly ceilings are contractual per user and are NOT published.
limit_count: 6
headers: {}
headers_note: >-
  No X-RateLimit-*, RateLimit-* or Retry-After headers are documented or observed. The Data
  License Hypermedia API returned no rate-limit headers on any anonymous probe of
  api.bloomberg.com (401/403 responses only). BLPAPI is a binary event protocol with no HTTP
  response headers at all.
responseCodes:
  throttled: null
  quotaExceeded: null
  note: >-
    Exhaustion is signalled as a ResponseError message with category LIMIT and sub-category
    DAILY_LIMIT_REACHED, MONTHLY_LIMIT_REACHED, FREE_TRIAL_TERM_LIMIT_REACHED or
    MANUALLY_DISABLED, or as SubscriptionTerminated with category LIMIT for concurrent
    subscriptions. See errors/bloomberg-applications-error-codes.yml.
limits:
  - name: Reference data request field cap
    scope: per-request
    metric: fields
    limit: 400
    applies:
      - Bloomberg Data API
      - Bloomberg Terminal Connect API
    evidence: '"400 fields for reference data request" — Request Size Restrictions'
  - name: Historical data request field cap
    scope: per-request
    metric: fields
    limit: 25
    applies:
      - Bloomberg Data API
      - Bloomberg Terminal Connect API
    evidence: '"25 fields for historical data request" — Request Size Restrictions'
  - name: Pending request ceiling
    scope: per-session
    metric: pending_requests
    limit: 1024
    applies:
      - Bloomberg Data API
      - Bloomberg Terminal Connect API
    evidence: >-
      "the number of requests many exceed the default 1,024 MaxPendingRequests limit" —
      Session.MaxPendingRequests default.
    note: >-
      The SDK splits a request into groups of 10 securities and 128 fields, so a wide request
      silently fans out into many pending requests and can breach this ceiling on its own.
  - name: Request fan-out chunking
    scope: per-request
    metric: securities_per_chunk
    limit: 10
    applies:
      - Bloomberg Data API
      - Bloomberg Terminal Connect API
    evidence: '"API will split the securities in the request into groups of 10 securities"'
  - name: Request fan-out chunking (fields)
    scope: per-request
    metric: fields_per_chunk
    limit: 128
    applies:
      - Bloomberg Data API
      - Bloomberg Terminal Connect API
    evidence: '"and fields into groups of 128 fields"'
  - name: Concurrent subscription limit
    scope: per-user
    metric: concurrent_subscriptions
    limit: null
    applies:
      - Bloomberg Data API
      - Bloomberg Terminal Connect API
    evidence: >-
      SubscriptionTerminated / LIMIT — "Concurrent subscription limit exceeded." The ceiling
      exists and is enforced; Bloomberg does not publish the number, it is set per contract.
undocumented_ceilings:
  - metric: daily_reference_data_hits
    signal: ResponseError LIMIT DAILY_LIMIT_REACHED
    note: Enforced per user; value set by contract, not published.
  - metric: monthly_reference_data_hits
    signal: ResponseError LIMIT MONTHLY_LIMIT_REACHED
    note: Enforced per user; value set by contract, not published.
  - metric: free_trial_term
    signal: ResponseError LIMIT FREE_TRIAL_TERM_LIMIT_REACHED
  - metric: max_devices_per_seat
    signal: Authorization Request LIMIT MAX_DEVICES_EXCEEDED
  - metric: max_simultaneous_authorizations
    signal: AuthorizationFailure LIMIT MAX_AUTHORIZATIONS_EXCEEDED
metering_model:
  unique_subscriptions: >-
    Subscriptions to the same security count once regardless of differing fields, options,
    interval or delayed status. Twenty subscriptions to "IBM US Equity" count as one.
  reference_data_hits: >-
    securities x fields x requests. The same request for 3 fields across 7 securities made 5
    times counts as 105 hits. Rows returned are irrelevant — tick history for 2 fields on one
    security counts as 2 even when thousands of rows come back.
  guidance: >-
    Bloomberg's own advice is to centralise and deduplicate requests, and to replace polling of
    fast-moving fields (BID/ASK every minute) with a subscription at a 1-minute interval, which
    it states "will dramatically reduce the number of reference data hits."
policies:
  - name: Slow consumer backpressure
    description: >-
      There is no Retry-After. The backpressure signal is an ADMIN SlowConsumerWarning message;
      ignoring it leads to DataLoss messages and silently dropped events. This is the runtime
      signal an agent must handle on this API.
tags:
  - Enterprise API
  - Market Data
  - Rate Limiting
  - Quotas
  - Throttling
maintainers:
  - FN: Kin Lane
    email: kin@apievangelist.com