What reference data does the API cover?

Three datasets: a hand-curated table of standard HTTP status codes (100-599) with messages, categories and descriptions; the full IANA mime-db of 2,600+ media types with charset, compressibility, source and file extensions; and the complete IANA root-zone TLD list of 1,400+ top-level domains. All three are bundled at the edge and queried through one API.

How do I authenticate my requests?

Authentication is a single query parameter. Append ?apikey=YOUR_KEY to any endpoint, for example GET /reference/v1/http-status/404?apikey=YOUR_KEY. You can also send the key as an X-Api-Key header. Create a free key at apicodex.io/register.

Why is the API so fast?

Every dataset is shipped to the edge and indexed in memory, so each lookup is an O(1) Map or Set hit with zero upstream calls. There are no third-party services to wait on and no cold dependencies, which means responses typically return in single-digit milliseconds from the network edge nearest your users.

Is matching case-sensitive, and how are dots handled?

Matching is case-insensitive across the board. MIME type lookups accept the URL-encoded type in any casing. File extension and TLD lookups tolerate a leading dot and any casing, so .COM, com, and COM all resolve identically. The status list category filter also accepts kebab and space variants such as client-error.

Can I list and filter results instead of looking up a single value?

Yes. /reference/v1/http-status lists every status code and accepts a category filter (Informational, Success, Redirection, Client Error, Server Error) plus a limit of 1-1000. /reference/v1/tlds lists top-level domains and accepts a lowercased startsWith prefix and a limit (default 200). The single-value endpoints return one entry; the list endpoints return a count, total, and an items/tlds array.

What happens when a code, type, or TLD is not recognized?

The API returns clear, documented error responses. Malformed input — like a non-3-digit status code, an invalid category, or an empty extension — returns a 400 with an error message and, where relevant, the list of allowed values. Unknown-but-well-formed values, such as an unknown MIME type or a status code outside the standard set, return a 404 echoing the value you queried.

Does the API make any external calls?

No. The Developer Reference API is fully offline by design. All data is bundled into the edge Worker, so there are no upstream lookups, no third-party rate limits, and no flaky dependencies. This makes it safe to put on a hot path like an API gateway validating Content-Type headers on every request.

HTTP status codes, MIME types & IANA TLDs in one edge API

Developer Reference API

The Developer Reference API is the single source of truth for the boring-but-essential lookups your code needs: what HTTP 425 means, the MIME type for a .heic file, and whether .zip is a real top-level domain.

It bundles a hand-curated table of standard HTTP status codes, the full IANA mime-db (2,600+ media types), and the complete IANA root-zone TLD list (1,400+ domains) into one clean JSON API served from the edge with zero upstream calls.

Get a free API key Read the docs

Free tier included, no credit card required. One key works across every API.

Free calls / month: 1,000
MIME Types: 2,600+
IANA TLDs: 1,400+
Lookup Speed: O(1)

Get your free API key

1,000 free calls on the free plan

Key features

Describe any standard HTTP status code (100-599)
List and filter status codes by category
Look up MIME type charset, compressibility, source and extensions
Resolve MIME type(s) from a file extension
Validate TLDs against the IANA root zone
List and prefix-search IANA top-level domains
Case-insensitive matching with leading-dot tolerance
Zero upstream calls — pure in-memory edge lookups

Built for

API gateways validating Content-Type headers
Devtools and dashboards rendering status-code docs
Domain-availability and registrar UIs
Email and file-upload validators
Translating codes or extensions into human-readable text
Content negotiation and compression decisions
Form validation for domain inputs
Backend services normalizing media types

MCP · for your agent

Hand the Developer Reference API to your agent

Connect Claude, Cursor or any MCP client once, then ask in plain words. Your agent finds this API, reads its docs and makes the call: 1 credit per call, the same as REST, from your team's balance.

Connect your agent

Explain unfamiliar error codes

“Our logs show a spike in 422 and 429 responses. What does each one mean, and which is on our side to fix?”

list_apis · get_api_docsfree

api_request GET /reference/v1/http-status/422 1 cr

Name, category and description of each status, with a note on which side needs fixing.

Set the right Content-Type

“Which Content-Type should our CDN send for .webmanifest, .avif and .wasm files?”

list_apis · get_api_docsfree

api_request GET /reference/v1/mime/extension/wasm 1 cr

The registered MIME type for each extension, ready to drop into the CDN config.

Stop rejecting valid domains

“Our signup form rejects emails on .lol, .ninja and .corp. Which of those top-level domains actually exist?”

list_apis · get_api_docsfree

api_request GET /reference/v1/tld/corp 1 cr

Whether each TLD is in the IANA root zone, so the form only blocks ones that don't exist.

$ claude mcp add --transport http apicodex https://mcp.apicodex.io

Illustrative asks; the calls and prices are real. Claude, Cursor, VS Code and Windsurf setup: mcp.apicodex.io

Try it

Build the request for your data

Edit the parameters below and see the exact request and curl command you'd send. No key required to preview.

GET /reference/v1/http-status/404

Open in Playground

Parameters

apikey

Request · HTTP

GET /reference/v1/http-status/404?apikey=YOUR_KEY HTTP/1.1
Host: api.apicodex.io

Response · JSON 200 OK

{
  "code": 404,
  "message": "Not Found",
  "category": "Client Error",
  "description": "The server cannot find the requested resource. The endpoint may be valid but the resource itself does not exist."
}

Run it with your key

Documentation

Developer Reference API Documentation

The Developer Reference API exposes fast, fully-offline lookups for HTTP status codes, IANA MIME types, and IANA top-level domains. All data is bundled at the edge, so responses are O(1) Map/Set lookups returned as clean JSON.

Base URL

url

https://api.apicodex.io/reference

Authentication

Authenticate every request by appending your API key as the apikey query parameter:

headers

GET /reference/v1/http-status/404?apikey=YOUR_KEY

Request and response

Illustrative values. Confirm current endpoint behavior, quotas, and data freshness in the API documentation before production use.

request · http

GET /reference/v1/http-status/404?apikey=YOUR_KEY HTTP/1.1
Host: api.apicodex.io

response · json

{
  "code": 404,
  "message": "Not Found",
  "category": "Client Error",
  "description": "The server cannot find the requested resource. The endpoint may be valid but the resource itself does not exist."
}

Code examples

cURL

curl --request GET \
  --url 'https://api.apicodex.io/reference/v1/mime/extension/json?apikey=YOUR_KEY'

JavaScript/Node.js

const params = new URLSearchParams({ apikey: 'YOUR_KEY' });

const response = await fetch(
  `https://api.apicodex.io/reference/v1/http-status/404?${params}`
);

const data = await response.json();
console.log(data);
// { code: 404, message: 'Not Found', category: 'Client Error', ... }

Python

import requests

url = "https://api.apicodex.io/reference/v1/tld/.COM"

querystring = {"apikey": "YOUR_KEY"}

response = requests.get(url, params=querystring)

print(response.json())
# {'tld': 'com', 'valid': True}

Endpoints

GET /v1/http-status/{code}

Describe one HTTP status code — returns message, category and description.

/v1/http-status/404?apikey=YOUR_KEY

GET /v1/http-status

List all known HTTP status codes, optionally filtered by category and limited.

/v1/http-status?category=Server%20Error&limit=2&apikey=YOUR_KEY

GET /v1/mime/type/{type}

Look up charset, compressibility, source and extensions for a URL-encoded MIME type.

/v1/mime/type/application%2Fjson?apikey=YOUR_KEY

GET /v1/mime/extension/{ext}

Return every MIME type associated with a file extension.

/v1/mime/extension/json?apikey=YOUR_KEY

GET /v1/tld/{tld}

Check whether a top-level domain exists in the IANA root zone list.

/v1/tld/.COM?apikey=YOUR_KEY

GET /v1/tlds

List IANA top-level domains, optionally filtered by prefix and limited.

/v1/tlds?startsWith=co&limit=3&apikey=YOUR_KEY

Query Parameters

Required parameters

apikey Your API key, passed as a query parameter on every request.

Optional parameters

category HTTP status list filter: Informational, Success, Redirection, Client Error or Server Error (case-insensitive; accepts kebab/space variants).
limit Maximum items to return (1-1000). Status list defaults to all; TLD list defaults to 200.
startsWith Lowercased prefix filter for the TLD list (letters, digits, hyphens).

Pricing

Developer Reference API Pricing

This API costs 1 credit per request. Credits are shared across every API on your plan.

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Drag the slider to match your expected request volume. We'll recommend the cheapest plan that covers it.

Requests per month 10,000

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$29.99 /month

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1,000 credits · ~1,000 requests/mo · 2 rps

All APIs included
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Full documentation and examples
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Up to 5 active API keys

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$29.99 /month

50,000 credits · ~50,000 requests/mo · 10 rps

All APIs included
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Usage dashboard and analytics
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Pro

$99.99 /month

250,000 credits · ~250,000 requests/mo · 25 rps

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Up to 5 active API keys

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FAQ

Developer Reference API

Key features

Built for

Hand the Developer Reference API to your agent

Explain unfamiliar error codes

Set the right Content-Type

Stop rejecting valid domains

Build the request for your data

Developer Reference API Documentation

Base URL

Authentication

Request and response

Code examples

Endpoints

GET /v1/http-status/{code}

GET /v1/http-status

GET /v1/mime/type/{type}

GET /v1/mime/extension/{ext}

GET /v1/tld/{tld}

GET /v1/tlds

Query Parameters

Required parameters

Optional parameters

Developer Reference API Pricing

Free

Starter

Pro

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Frequently asked questions

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