generated: '2026-07-27'
method: searched
source: https://www.iso-ne.com/participate/support/web-services-data
also_sourced_from:
- https://webservices.iso-ne.com/docs/v1.1/
- openapi/iso-new-england-web-services-openapi.yml
- anonymous probes of https://webservices.iso-ne.com/api/v1.1 on 2026-07-27
description: >-
  Cross-cutting request/response semantics of the ISO New England Web Services API v1.1, taken from
  ISO New England's own documentation and from the harvested OpenAPI. This is a read-only market and
  operations data API: all 489 documented path templates are GET, and no write, batch, or
  long-running operation exists. Conventions ISO New England does not publish are recorded as absent
  rather than guessed.

authentication:
  style: HTTP Basic over SSL
  credential: ISO Express account username and password
  header: 'Authorization: Basic <base64(user:password)>'
  anonymous_access: false
  evidence: 'Anonymous GET https://webservices.iso-ne.com/api/v1.1 -> HTTP 401 with a Basic challenge (2026-07-27).'
  detail: authentication/iso-new-england-authentication.yml
  note: >-
    There is no API key, no OAuth 2.0, no OpenID Connect and no mTLS on this API. Credentials are
    the same ISO Express web credentials, which ISO New England states are automatically granted
    access to the public data feeds.

content_negotiation:
  formats: [application/xml, application/json]
  default: application/xml
  selection:
  - style: url-extension
    example: https://webservices.iso-ne.com/api/v1.1/fiveminutelmp/current.json
    note: Append .xml or .json to the request URL.
  - style: accept-header
    example: 'Accept: application/json'
  json_mapping:
    note: >-
      JSON is a direct mapping of the XML schema. XML attributes appear as "@name" properties and
      element text as "$" - confirmed against real payloads (see examples/). The response is wrapped
      in the plural element (e.g. {"FiveMinLmps": {"FiveMinLmp": [...]}}), and a single-item result
      may be an object rather than an array.
  schemas:
  - schemas/iso-new-england-web-services-ns0.xsd
  - schemas/iso-new-england-web-services-ns1.xsd
  - json-schema/iso-new-england-web-services-schemas.json

versioning:
  scheme: uri-path
  current: v1.1
  base_path: https://webservices.iso-ne.com/api/v1.1
  deployed: November 2013
  docs: https://www.iso-ne.com/participate/support/web-services-data
  note: >-
    Version 1.1 has been the current version since November 2013. The resource set is extended in
    place (Batteries fuel category added May 2026) rather than by cutting a new version.

resource_shape:
  read_only: true
  methods: [GET]
  operation_count: 489
  root_resources: 91
  patterns:
  - pattern: /<resource>/current
    meaning: The most recent interval/report the feed has published.
  - pattern: /<resource>/day/{day}
    meaning: A whole operating day, day formatted YYYYMMDD.
  - pattern: /<resource>/month/{month}
    meaning: A whole month, month formatted YYYYMM.
  - pattern: /<resource>/year/{year}
    meaning: A whole year, year formatted YYYY.
  - pattern: /<resource>/location/{locationId}
    meaning: Filter to one pricing/load location id (see vocabulary/iso-new-england-vocabulary.yml).
  - pattern: /<resource>/locationType/{locationType}
    meaning: Filter to a class of locations (HUB, LOAD ZONE, EXT. NODE, INT. AREA ...).
  - pattern: /<resource>/info
    meaning: >-
      Feed freshness. Returns a ServiceInfo element with CreationDate and LatestBeginDate - the
      closest thing this API has to a cache/freshness signal. Poll /info before re-pulling a feed.
  - pattern: /<resource>/all
    meaning: The unfiltered set for the current interval.
  parameters:
    style: path-only
    query_parameters: none documented
    formats_reference: https://www.iso-ne.com/participate/support/web-services-data
    vocabulary: vocabulary/iso-new-england-vocabulary.yml

pagination:
  supported: false
  note: >-
    No pagination is documented and none was observed. Volume is bounded by the time window in the
    path (current / day / month / year) and by location filters. Bulk history is served as CSV files
    from ISO Express instead (https://www.iso-ne.com/isoexpress/), not through this API.

idempotency:
  idempotency_key: false
  note: >-
    The API is read-only - every operation is a GET and is therefore idempotent by HTTP semantics -
    but ISO New England publishes no idempotency-key contract, because there is nothing to write.
    No Idempotency pointer is claimed for this provider.

field_selection:
  expansion: false
  sparse_fields: false
  note: Responses are fixed-shape XSD types; no expansion or field-selection mechanism is documented.

request_tracing:
  request_id_header: none documented
  note: No correlation/request-id header is documented, and none was returned on the 401 responses observed.

rate_limiting:
  documented: false
  headers: none documented
  note: >-
    ISO New England documents no rate limit, quota, or throttling headers for the Web Services API,
    and none could be observed without credentials. The /info endpoints and the publication cadence
    of each feed (five-minute, fifteen-minute, hourly, daily) are the practical polling guide.
  guidance: >-
    Poll no faster than the feed publishes. Five-minute feeds update every five minutes; hourly and
    day-ahead feeds update on their market schedule.

caching:
  headers: none documented
  freshness_endpoint: /<resource>/info
  note: >-
    Use the per-resource /info endpoint (ServiceInfo.CreationDate and ServiceInfo.LatestBeginDate) to
    decide whether new data exists before pulling a full interval.

errors:
  envelope: none published
  problem_json: false
  catalog: errors/iso-new-england-problem-types.yml
  note: 401 is the only error status confirmed by probe; there is no documented error-code registry.

events:
  webhooks: false
  streaming: false
  asyncapi: false
  note: >-
    ISO New England publishes no webhooks, no streaming/push surface and no AsyncAPI. Change
    notification is by polling, by the ISO Express report trees, or by the ISO's mailing lists and
    Web Feeds page (https://www.iso-ne.com/participate/support/feeds).

alternatives_to_the_api:
  bulk_csv: https://www.iso-ne.com/isoexpress/
  note: >-
    Full historical report files download anonymously as CSV from ISO Express (verified: a 2.46 MB
    day-ahead nodal LMP file returned HTTP 200 with no account on 2026-07-27). The API is the
    per-resource, credentialed path to the same data.

cross_links:
  authentication: authentication/iso-new-england-authentication.yml
  errors: errors/iso-new-england-problem-types.yml
  lifecycle: lifecycle/iso-new-england-lifecycle.yml
  vocabulary: vocabulary/iso-new-england-vocabulary.yml
  data_model: data-model/iso-new-england-data-model.yml
  examples: examples/_index.yml