4chan Read-Only API
Free read-only 4chan API with no key: board metadata, thread catalogs, full threads and post data as JSON, served from a static CDN. Tested example included.
Endpoint tested and returned HTTP 200 on 2026-08-21
What is the 4chan Read-Only API?
The 4chan API is a free, read-only, key-free JSON API served from the a.4cdn.org static host. It exposes board metadata and configuration, thread catalogs, full thread contents and individual post data. It is read-only by design — posting is not possible through it.
This API is worth understanding as an engineering artefact regardless of what you think of the site. It is entirely static JSON served from a CDN, with no query parameters and no server-side computation: every endpoint is a file. That design is why it absorbs enormous traffic, and it is a good illustration of how far a read-only API can get on static generation alone.
The `/boards.json` endpoint documented here is the sensible entry point because it returns every board's configuration in one response — page count, posting cooldowns, maximum file sizes, comment limits and a `ws_board` flag marking whether a board is work-safe. That last field is the one to build on: filtering to `ws_board: 1` is the difference between a usable integration and an unusable one. **A significant portion of this site hosts adult and offensive content, so read the caveats before shipping anything against it.**
Quick facts
- Base URL
https://a.4cdn.org- Authentication
- No API key. Read-only: there is no write, post or authenticate operation. The terms require a 1-second minimum interval between requests and forbid requesting the same resource more often than once a second.
- Rate limit
- One request per second, enforced by policy. Use `If-Modified-Since` and honour 304 responses rather than re-downloading.
- Pricing
- Free.
- CORS
- Not enabled — call it from your server
- Official docs
- Read the docs
How to use the 4chan Read-Only API
Every request below was executed against the live API on 2026-08-21, and the response shown is the real body it returned — not an illustration.
1. List every board with its configuration
GET https://a.4cdn.org/boards.json
curl 'https://a.4cdn.org/boards.json'const res = await fetch("https://a.4cdn.org/boards.json");
if (!res.ok) throw new Error(`Request failed: ${res.status}`);
const data = await res.json();
console.log(data);import requests
res = requests.get("https://a.4cdn.org/boards.json", timeout=20)
res.raise_for_status()
print(res.json()){
"boards": [
{
"board": "3",
"title": "3DCG",
"ws_board": 1,
"per_page": 15,
"pages": 10,
"max_filesize": 4194304,
"max_webm_filesize": 4194304,
"max_comment_chars": 2000,
"max_webm_duration": 120,
"bump_limit": 310,
"image_limit": 150,
"cooldowns": {
"threads": 600,
"replies": 60,
"images": 60
},
"meta_description": ""/3/ - 3DCG" is 4chan's board for 3D modeling and imagery.",
"is_archived": 1
},
{
"board": "a",
"title": "Anime & Manga",
"ws_board": 1,
"per_page": 15,
"pages": 10,
"max_filesize": 4194304,
"max_webm_filesize": 4194304,
"max_comment_chars": 2000,
"max_webm_duration": 120,
"bump_limit": 500,
"image_limit": 300,
"cooldowns": {
"threads": 600,
"replies": 60,
"images": 60
},
"meta_description": ""/a/ - Anime & Manga" is 4chan's imageboard dedicated to the discussion of Japanese animation and manga.",
"spoilers": 1,
"custom_spoilers": 1,
"is_archived": 1
},
{
"board": "aco",
"title": "Adult Cartoons",
"ws_board": 0,
"per_page": 15,
"pages": 10,
"max_filesize": 4194304,
"max_webm_filesize": 4194304,
"max_comment_chars": 2000,
"max_webm_duration": 120,
"bump_limit": 300,
"image_limit": 300,
"cooldowns": {
"threads": 600,
"replies": 60,
"images": 30
},
"meta_description": ""Parameters
| Parameter | Type | Required | Description |
|---|---|---|---|
(boards.json) | path segment | Optional | Static file listing every board and its settings. Takes no parameters. |
board | path segment | Optional | Board short name, used as the first segment for thread endpoints. g |
(catalog.json) | path segment | Optional | All threads on a board with their opening posts and reply counts. |
(thread/{no}.json) | path segment | Optional | One complete thread including every reply. 12345678 |
(threads.json) | path segment | Optional | Thread ids with last-modified times, designed for cheap change detection. |
Response fields
boardsarray- Every board on the site with its full configuration.
board / titlestring- Short code (`g`, `3`) and human-readable title.
ws_boardinteger- 1 if the board is work-safe, 0 if not. Filter on this before displaying anything.
pages / per_pageinteger- How many pages the board has and how many threads per page.
max_filesize / max_webm_filesizeinteger- Upload limits in bytes.
cooldownsobject- Minimum seconds between posting threads, replies and images.
bump_limit / image_limitinteger- When a thread stops bumping and stops accepting images.
meta_descriptionstring- Board description, HTML-escaped — decode entities before display.
What you can build with the 4chan Read-Only API
- Build a read-only board archiver or research dataset
- Study static-file API design as an architecture example
- Monitor thread activity with cheap `If-Modified-Since` polling
- Aggregate public post metadata for academic discourse research
Common errors and how to fix them
404
Unknown board, or a thread that has been pruned.
Fix: Threads are deleted as they fall off the last page. A 404 usually means the thread is simply gone, which is normal.
429
More than one request per second.
Fix: The rate limit is policy, not a suggestion. Space requests at least a second apart and use `If-Modified-Since` so unchanged resources return a cheap 304.
HTML entities in text
Post text is HTML-escaped and contains markup.
Fix: Comment fields include `<br>` and quote links. Decode entities and sanitise before rendering — never inject raw.
4chan Read-Only API — frequently asked questions
Is the 4chan API free and does it need a key?
Yes, it is free with no API key. It is also strictly read-only — there is no endpoint for posting, authenticating or modifying anything.
What are the rate limits?
One request per second, and you must not request the same resource more than once a second. The API supports `If-Modified-Since`, so honour 304 responses rather than re-downloading unchanged files.
How do I avoid pulling adult content?
Filter on the `ws_board` field from the boards endpoint, which is 1 for work-safe boards and 0 otherwise. A large portion of the site is not work-safe, so this filter is essential rather than optional for most integrations.
Why is the API just static JSON files?
It is a deliberate design choice. Every endpoint is a pre-generated file on a CDN with no query parameters and no server-side computation, which is how it absorbs very high traffic cheaply — a genuinely instructive example of read-only API architecture.
Tools that pair with this API
JSON Formatter
Format, beautify and minify JSON online with 2-space, 4-space or tab indentation. Sort keys alphabetically and catch syntax errors instantly — free and private.
Strip HTML Tags
Remove all HTML tags and convert markup to clean plain text. Decode HTML entities and keep line breaks for block elements like paragraphs and headings.
JSON to CSV Converter
Convert a JSON array of objects to CSV online. Automatic column headers from the union of all keys, delimiter choice and proper quoting — all in-browser.
4chan Read-Only API is an independent third-party service and is not affiliated with ByteTools or ByteVancer. Details on this page were verified on 2026-08-21; always check the official documentation before relying on this API in production, as terms and limits can change.