CRC32 API

Request parameters

Response fields

A successful response is {"ok":true,"data":{…}}. These fields are inside data.

hex · string

Returned hex.

decimal · integer

Returned decimal. Range: 0–4294967295.

Match the CRC variant

This API implements CRC-32/ISO-HDLC, commonly called IEEE CRC-32, using reflected polynomial 0xEDB88320, initial register 0xFFFFFFFF and final XOR 0xFFFFFFFF. It is the familiar variant used by ZIP and Ethernet checksums. It is not CRC32C/Castagnoli, and those two variants produce different values for the same input.

Representations and intended use

The hex value always contains eight lowercase digits, including leading zeroes. The decimal value is an unsigned 32-bit integer and can be compared without signed-integer conversion. CRC32 is intended to detect accidental changes; it is not a cryptographic integrity or authentication mechanism. This endpoint processes text rather than uploaded files.

cURL, JavaScript and Python examples

curl --fail-with-body --request POST 'https://www.base64.sh/api/v1/crc32-checksum/' \
  --user-agent 'Base64.sh API example/1.0' --header 'Content-Type: application/json' \
  --data-raw '{"text":"123456789"}'

const response = await fetch("https://www.base64.sh/api/v1/crc32-checksum/", {
  method: "POST",
  headers: { "Content-Type": "application/json" },
  body: JSON.stringify({
  "text": "123456789"
})
});
if (!response.ok) throw new Error(await response.text());
console.log(await response.json());

import json
from urllib.request import Request, urlopen

payload = json.loads("{\n  \"text\": \"123456789\"\n}")
request = Request(
    "https://www.base64.sh/api/v1/crc32-checksum/",
    data=json.dumps(payload, ensure_ascii=False).encode("utf-8"),
    headers={"Content-Type": "application/json", "User-Agent": "Base64.sh API example/1.0"},
    method="POST",
)
with urlopen(request, timeout=15) as response:
    print(json.load(response))

{
  "ok": true,
  "data": {
    "hex": "cbf43926",
    "decimal": 3421780262
  }
}

curl --fail-with-body --request POST 'https://www.base64.sh/api/v1/crc32-checksum/' \
  --user-agent 'Base64.sh API example/1.0' --header 'Content-Type: application/json' \
  --data-raw '{"text":""}'

const response = await fetch("https://www.base64.sh/api/v1/crc32-checksum/", {
  method: "POST",
  headers: { "Content-Type": "application/json" },
  body: JSON.stringify({
  "text": ""
})
});
if (!response.ok) throw new Error(await response.text());
console.log(await response.json());

import json
from urllib.request import Request, urlopen

payload = json.loads("{\n  \"text\": \"\"\n}")
request = Request(
    "https://www.base64.sh/api/v1/crc32-checksum/",
    data=json.dumps(payload, ensure_ascii=False).encode("utf-8"),
    headers={"Content-Type": "application/json", "User-Agent": "Base64.sh API example/1.0"},
    method="POST",
)
with urlopen(request, timeout=15) as response:
    print(json.load(response))

{
  "ok": true,
  "data": {
    "hex": "00000000",
    "decimal": 0
  }
}

Invalid request example

{
  "text": 123
}

HTTP 400

{
  "ok": false,
  "error": {
    "code": "INVALID_INPUT",
    "message": "text must be a string."
  }
}

Limits and error handling

Requests require Content-Type: application/json and a UTF-8 JSON object. The body limit is 32 KiB (32,768 bytes), text fields allow up to 16,384 Unicode code points unless a smaller limit is listed, and responses are limited to 256 KiB. Unknown parameters and unpaired Unicode surrogates in parameter strings are rejected. Send inputs in the request body, not query parameters.

Anonymous access is limited to approximately 60 POST requests per minute per IP address, shared across endpoints in each Cloudflare location. Shared networks share the allowance. Counters are eventually consistent, not a guaranteed global quota. On HTTP 429, wait for the Retry-After interval before retrying; avoid immediate retry loops.

Programmatic clients should send an identifying User-Agent, as shown in the cURL and Python examples. Browser fetch supplies its own header. Cloudflare may reject a generic or missing agent before the API runs; an edge-generated 403 can be plain text or HTML rather than the JSON envelope. See Cloudflare error 1010.

400 · Invalid input

Malformed JSON, missing fields, unsupported options or invalid encoded text. Correct the input before retrying.

403 · Edge request blocked

Check the User-Agent and the Cloudflare error response before retrying.

404 · Unknown endpoint

Use a documented /api/v1/{tool}/ endpoint.

405 · Method not allowed

Use POST. OPTIONS is supported for browser CORS requests.

413 · Size limit exceeded

Reduce the request size or the generated output.

415 · Unsupported media type

Set Content-Type: application/json.

429 · Rate limited

Wait at least the Retry-After number of seconds.

500 / 503 · Service unavailable

Retry later with bounded backoff. Availability is not guaranteed.

API data processing

API inputs are sent over HTTPS and processed in memory by a Cloudflare Worker. The application does not persist submitted text or deliberately log request bodies, and API responses use Cache-Control: no-store. Cloudflare may process network metadata under its own policies. For local processing, use the corresponding browser tool. See the privacy policy.