generated: '2026-07-28'
method: searched
source: >-
  https://consultations.caa.co.uk/api/2.0/ , /2.1/ , /2.2/ , /2.3/ , /2.4/ — all
  five fetched 2026-07-28 (HTTP 200) and diffed against each other.
description: >-
  The UK Civil Aviation Authority publishes no dated API changelog. It does,
  however, serve every historical version of the Citizen Space consultations API
  concurrently, each with its own complete reference page. This artifact is the
  version history reconstructed from those five pages: each entry records what the
  version's own reference page documents that the previous version's did not. No
  dates are published for any version, so `date` is null throughout — that is
  recorded absence, not an omission on our side.
scheme: uri-path
current: '2.4'
changelog_url: null
version_index: https://consultations.caa.co.uk/api/
entries:
  - version: '2.4'
    date: null
    docs: https://consultations.caa.co.uk/api/2.4/
    breaking: false
    summary: >-
      "Version 2.4 is a minor update to Version 2.3, updating the values of the
      'type_string' extended attribute." (verbatim from the reference page)
    additions:
      - Parameter `at` — "Activity type. Must be one of the activity types available to the site."
      - Response field `activity_type` — "The activity type ID" (basic tier).
    deprecations:
      - Parameter `ct` relabelled "(deprecated) Legacy activity type".
      - Response field `type` relabelled "(deprecated) The legacy type".
    removals:
      - >-
        The `callback` (jsonp) parameter documented in 2.3 is not listed on the 2.4
        reference page. Recorded as undocumented-in-2.4; not tested for removal.
  - version: '2.3'
    date: null
    docs: https://consultations.caa.co.uk/api/2.3/
    breaking: false
    summary: >-
      The largest expansion in the series: a second method, the workspace model, and
      the full "all" field tier.
    additions:
      - Method `json_consultation_details` (dept + id required, fields optional) with a documented 404.
      - Parameter `callback` — "Used to enable jsonp requests".
      - Response fields `workspace_title` and `workspace_id`.
      - >-
        Response fields at the "all" tier — why, what_happens_next, feedbackdate,
        resultsdate, contact_name, contact_jobtitle, contact_team, contact_phone,
        contact_email, related_links, related_consultations, supporting_documents.
      - Audiences, areas and interests promoted from bare id lists to {id, name} objects.
    deprecations:
      - Response field `department` relabelled "(deprecated) The name of the department"; superseded by workspace_title.
      - Response field `dept` relabelled "(deprecated) The ID of the department"; superseded by workspace_id.
  - version: '2.2'
    date: null
    docs: https://consultations.caa.co.uk/api/2.2/
    breaking: false
    summary: Adds a direct participation link to the extended field tier.
    additions:
      - >-
        Response field `participation_url` — "The direct URL to the participation
        method (survey etc), skipping the overview page (extended and above)".
  - version: '2.1'
    date: null
    docs: https://consultations.caa.co.uk/api/2.1/
    breaking: true
    summary: >-
      Replaces the boolean `extended` switch with the three-valued `fields`
      parameter and introduces the "all" tier.
    additions:
      - Parameter `fields` with permissible values basic, extended and all (default basic).
      - Response fields `audiences`, `areas` and `interests` at the "all" tier.
    removals:
      - >-
        Parameter `extended` ("This will return extra information about each
        activity, but is slower"), documented in 2.0 and gone from 2.1 onward.
  - version: '2.0'
    date: null
    docs: https://consultations.caa.co.uk/api/2.0/
    breaking: false
    summary: >-
      Baseline. One method, `json_search_results`, with the tx/pc/st/au/in/de/ar/
      dk/fd/td/ct search parameters, a boolean `extended` switch, and the id, title,
      url, status, overview, startdate, enddate, department, type, type_string,
      progress and visibility response fields.
notes:
  - >-
    Every version listed remains live and returns data; none has been withdrawn.
    Verified 2026-07-28.
  - >-
    This is the consultation-platform vendor's version history as deployed on a CAA
    domain, not a CAA aviation-data release history. The CAA publishes no changelog
    for the G-INFO register, ATOL data or its statistical series — those are
    republished as dated files.