openapi: 3.0.3
info:
  title: 4chan Read-Only JSON Archive Threads API
  description: 'Read-only JSON API for the 4chan and 4channel imageboards, originally launched in September 2012. All endpoints are served as static JSON documents from `a.4cdn.org` over `http://` or `https://`. The API exposes only the public, anonymous read surface of the site: board metadata, board catalogs, board threadlists, archive listings, board index pages, and individual thread documents.

    There is no authentication, no posting, and no per-user write surface. Only `GET`, `HEAD`, and `OPTIONS` are accepted. CORS is enabled only for origins `boards.4chan.org` and `boards.4channel.org`.

    Clients MUST send no more than one request per second, MUST set thread-polling intervals to at least 10 seconds (preferably higher), and SHOULD use `If-Modified-Since` so that unchanged threads return `304 Not Modified`.'
  version: '2026-05-28'
  termsOfService: https://github.com/4chan/4chan-API#api-terms-of-service
  contact:
    name: 4chan API
    email: api@4chan.org
    url: https://github.com/4chan/4chan-API
  license:
    name: 4chan API Terms of Service
    url: https://github.com/4chan/4chan-API#api-terms-of-service
  x-generated-from: documentation
  x-source-url: https://github.com/4chan/4chan-API
  x-last-validated: '2026-05-28'
servers:
- url: https://a.4cdn.org
  description: Production 4chan read-only JSON API (HTTPS).
- url: http://a.4cdn.org
  description: Production 4chan read-only JSON API (HTTP, legacy clients only).
tags:
- name: Threads
  description: Single-thread document containing the OP and every reply.
paths:
  /{board}/thread/{thread}.json:
    get:
      operationId: getThread
      summary: 4chan Get Thread
      description: 'Returns the full document for a single thread on the given board: the OP post object followed by every reply. To poll a thread for new replies, send `If-Modified-Since` on subsequent requests and treat `304` as "no change"; the minimum polling interval per the 4chan API rules is 10 seconds, with longer intervals preferred.'
      tags:
      - Threads
      parameters:
      - $ref: '#/components/parameters/BoardPath'
      - $ref: '#/components/parameters/ThreadPath'
      responses:
        '200':
          description: Successful response. Returns the thread's posts array.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/ThreadResponse'
              examples:
                GetThread200Example:
                  summary: Default getThread 200 response
                  x-microcks-default: true
                  value:
                    posts:
                    - false: 570368
                      sticky: 1
                      closed: 1
                      now: 12/31/18(Mon)17:05:48
                      name: Anonymous
                      sub: Welcome to /po/!
                      com: Welcome to /po/! We specialize in origami and papercraft.
                      filename: yotsuba_folding
                      ext: .png
                      w: 530
                      h: 449
                      tn_w: 250
                      tn_h: 211
                      tim: 1546293948883
                      time: 1546293948
                      md5: uZUeZeB14FVR+Mc2ScHvVA==
                      fsize: 516657
                      resto: 0
                      capcode: mod
                      semantic_url: welcome-to-po
                      replies: 2
                      images: 2
                      unique_ips: 1
                    - false: 570370
                      now: 12/31/18(Mon)17:14:56
                      name: Anonymous
                      com: FAQs about papercraft.
                      filename: papercraft faq
                      ext: .png
                      w: 318
                      h: 704
                      tn_w: 56
                      tn_h: 125
                      tim: 1546294496751
                      time: 1546294496
                      md5: 0EqXBb4gGIyzQiaApMdFAA==
                      fsize: 285358
                      resto: 570368
                      capcode: mod
        '304':
          description: Not Modified.
        '404':
          description: Board not found or thread does not exist.
        '503':
          description: Service Unavailable.
      x-microcks-operation:
        delay: 0
        dispatcher: FALLBACK
components:
  schemas:
    ThreadResponse:
      type: object
      description: Top-level response from `/{board}/thread/{thread}.json`.
      required:
      - posts
      properties:
        posts:
          type: array
          description: The OP followed by every reply in the thread, in chronological order.
          items:
            $ref: '#/components/schemas/Post'
    Post:
      type: object
      description: A single post — either an OP (when `resto == 0`) or a reply (when `resto` is the OP id). Many fields appear only on OPs (`replies`, `images`, `sticky`, `closed`, `archived`, …) or only on posts with an attached file.
      required:
      - 'no'
      - resto
      - now
      - time
      - name
      properties:
        'no':
          type: integer
          description: Numeric post ID.
          example: 570368
        resto:
          type: integer
          description: For replies, the OP ID this post replies to. For OPs, `0`.
          example: 0
        sticky:
          type: integer
          description: '`1` if the thread is pinned to the top of the board (OP only).'
          enum:
          - 0
          - 1
          example: 1
        closed:
          type: integer
          description: '`1` if the thread is closed to new replies (OP only).'
          enum:
          - 0
          - 1
          example: 1
        now:
          type: string
          description: Localized post timestamp in `MM/DD/YY(Day)HH:MM` (or `HH:MM:SS`) format, EST/EDT.
          example: 12/31/18(Mon)17:05:48
        time:
          type: integer
          description: UNIX timestamp the post was created.
          example: 1546293948
        name:
          type: string
          description: Display name used for the post (defaults to `Anonymous`).
          example: Anonymous
        trip:
          type: string
          description: User tripcode in the form `!tripcode` or `!!securetripcode`.
          example: '!K.WeEabc'
        id:
          type: string
          description: Poster ID (8 chars) — present only when the board has per-thread poster IDs enabled.
          example: ABcd1234
        capcode:
          type: string
          description: Staff capcode on the post.
          enum:
          - mod
          - admin
          - admin_highlight
          - manager
          - developer
          - founder
          example: mod
        country:
          type: string
          description: ISO 3166-1 alpha-2 country code of the poster, or `XX` if unknown.
          example: US
        country_name:
          type: string
          description: Human-readable country name of the poster.
          example: United States
        board_flag:
          type: string
          description: Board-specific flag code (only on boards with board flags enabled).
          example: AB
        flag_name:
          type: string
          description: Board-specific flag display name.
          example: Flag Name AB
        sub:
          type: string
          description: OP subject (OP only, when set).
          example: Welcome to /po/!
        com:
          type: string
          description: Post comment as HTML-escaped string.
          example: Welcome to /po/! We specialize in origami, papercraft, and everything that's relevant to paper engineering.
        tim:
          type: integer
          description: UNIX timestamp + microtime that the attachment was uploaded — also the file ID for `i.4cdn.org`.
          example: 1546293948883
        filename:
          type: string
          description: Original filename of the attachment as uploaded.
          example: yotsuba_folding
        ext:
          type: string
          description: Attachment file extension.
          enum:
          - .jpg
          - .png
          - .gif
          - .pdf
          - .swf
          - .webm
          example: .png
        fsize:
          type: integer
          description: Attachment file size, in bytes.
          example: 516657
        md5:
          type: string
          description: 24-character packed base64 MD5 hash of the attachment.
          example: uZUeZeB14FVR+Mc2ScHvVA==
        w:
          type: integer
          description: Attachment width in pixels.
          example: 530
        h:
          type: integer
          description: Attachment height in pixels.
          example: 449
        tn_w:
          type: integer
          description: Thumbnail width in pixels.
          example: 250
        tn_h:
          type: integer
          description: Thumbnail height in pixels.
          example: 211
        filedeleted:
          type: integer
          description: '`1` if the post had a file and that file has been deleted.'
          enum:
          - 0
          - 1
          example: 0
        spoiler:
          type: integer
          description: '`1` if the attachment is spoilered.'
          enum:
          - 0
          - 1
          example: 0
        custom_spoiler:
          type: integer
          description: Custom spoiler ID `1-10` (only on boards with custom spoilers).
          minimum: 1
          maximum: 10
          example: 1
        replies:
          type: integer
          description: Total number of replies in the thread (OP only).
          example: 2
        images:
          type: integer
          description: Total number of image replies in the thread (OP only).
          example: 2
        bumplimit:
          type: integer
          description: '`1` once the thread has reached its bump limit (OP only).'
          enum:
          - 0
          - 1
          example: 0
        imagelimit:
          type: integer
          description: '`1` once the thread has reached its image-reply limit (OP only).'
          enum:
          - 0
          - 1
          example: 0
        tag:
          type: string
          description: Category of `.swf` upload on `/f/` (OP only, `/f/` only).
          example: Game
        semantic_url:
          type: string
          description: SEO-friendly URL slug for the thread (OP only).
          example: welcome-to-po
        since4pass:
          type: integer
          description: Year the poster bought a 4chan Pass (only when the poster opted in).
          example: 2018
        unique_ips:
          type: integer
          description: Number of unique posters in the thread (OP only, only when the thread is live).
          example: 1
        m_img:
          type: integer
          description: '`1` if a mobile-optimized variant of the attachment exists.'
          enum:
          - 0
          - 1
          example: 1
        archived:
          type: integer
          description: '`1` once the thread has been archived (OP only).'
          enum:
          - 0
          - 1
          example: 1
        archived_on:
          type: integer
          description: UNIX timestamp the thread was archived (OP only).
          example: 1566530948
        omitted_posts:
          type: integer
          description: Replies omitted from a catalog/index preview (OP only on catalog/index responses).
          example: 1
        omitted_images:
          type: integer
          description: Image replies omitted from a catalog/index preview (OP only on catalog/index responses).
          example: 1
        last_modified:
          type: integer
          description: UNIX timestamp the thread was last modified (OP only on catalog/threadlist responses).
          example: 1566530948
        last_replies:
          type: array
          description: Most recent reply objects shown in a catalog preview (OP only on catalog responses).
          items:
            $ref: '#/components/schemas/Post'
  parameters:
    BoardPath:
      name: board
      in: path
      required: true
      description: Board directory short name (e.g. `a`, `b`, `g`, `pol`, `po`, `v`). The full list of valid values is the `board` field on each entry in `/boards.json`.
      schema:
        type: string
        pattern: ^[a-z0-9]+$
        minLength: 1
        maxLength: 8
        example: po
      example: po
    ThreadPath:
      name: thread
      in: path
      required: true
      description: The OP number of the thread to retrieve.
      schema:
        type: integer
        minimum: 1
        example: 570368
      example: 570368