Line Length

{
  "asOf": "2026-10-11T14:32:44.449Z",
  "avgCharWidthEm": 0.5,
  "charactersPerLine": 80,
  "degraded": false,
  "disclaimer": "Screening signal computed from the named public source. Not financial, legal or investment advice; provided as is. Verify at the source before acting.",
  "fontSizePx": 18,
  "minimumLineHeight": 1.5,
  "minimumParagraphSpacingMultipleOfLineSpacing": 1.5,
  "notChecked": [
    "the real font: characters per line varies with the typeface, language and text (CJK counts characters, not words)",
    "multi-column text, where 40 to 50 characters is acceptable",
    "…2 more"
  ],
  "reasons": [
    "Within the usual 45 to 75 range (66 is the classic ideal).",
    "An estimate: set max-width in ch units so the browser measures the real font."
  ],
  "source": "Bringhurst's 45 to 75 character guideline (66 ideal) and WCAG 2.2 criterion 1.4.8 (80 characters), with the estimate computed locally",
  "suggestedCss": "max-width: 66ch;",
  "summary": "About 80 characters per line (720px column, 18px type, 0.5em average glyph): long.",
  "verdict": "LONG",
  "wcagAaaLineLimit": 80,
  "wcagTextSpacingOverridePx": {
    "letterSpacing": 2.16,
    "lineHeight": 27,
    "paragraphSpacing": 36,
    "wordSpacing": 2.88
  },
  "widthFor45Px": 405,
  "widthFor66Em": 33,
  "widthFor66Px": 594,
  "widthFor75Px": 675,
  "widthFor80Px": 720,
  "widthPx": 720,
  "withinWcagAaa": true
}

# bash or zsh: see the payment challenge. Nothing is charged.
curl -sS -g -i 'https://css-design-calc.x402tookit.com/line-length?avgCharWidthEm=0.5&fontSizePx=18&widthPx=720'

# x402 v2 sends the challenge base64-encoded in the PAYMENT-REQUIRED header (v1 sends it in the body).
# To read the header:
curl -sS -g -o /dev/null -D - 'https://css-design-calc.x402tookit.com/line-length?avgCharWidthEm=0.5&fontSizePx=18&widthPx=720' \
  | grep -i '^payment-required:' | cut -d' ' -f2 | tr -d '\r' | base64 --decode

// npm i @x402/fetch @x402/evm viem
import { wrapFetchWithPayment, x402Client } from "@x402/fetch";
import { registerExactEvmScheme } from "@x402/evm/exact/client";
import { privateKeyToAccount } from "viem/accounts";

// Pays at most $0.02 per call.
const client = new x402Client().setSpendControls({ maxAmountPerPayment: "$0.02" });
registerExactEvmScheme(client, { signer: privateKeyToAccount(process.env.EVM_PRIVATE_KEY) });
const pay = wrapFetchWithPayment(fetch, client);

// Not sure it's safe to pay? ToolVet checks it first for $0.005. Pay for that from a separate
// client: this one is capped at $0.02 per payment. GET https://toolvet.app/api/v1/check?url=https%3A%2F%2Fcss-design-calc.x402tookit.com%2Fline-length
const res = await pay("https://css-design-calc.x402tookit.com/line-length?avgCharWidthEm=0.5&fontSizePx=18&widthPx=720");
console.log(res.status, await res.text());

# pip install "x402[requests,evm]"
import os
from eth_account import Account
from x402 import x402ClientSync
from x402.http.clients import x402_requests
from x402.mechanisms.evm import EthAccountSigner
from x402.mechanisms.evm.exact.register import register_exact_evm_client

# Pays at most $0.02 per call.
client = x402ClientSync().set_spend_controls({"max_amount_per_payment": "$0.02"})
register_exact_evm_client(client, EthAccountSigner(Account.from_key(os.environ["EVM_PRIVATE_KEY"])))

with x402_requests(client) as session:
    res = session.get("https://css-design-calc.x402tookit.com/line-length?avgCharWidthEm=0.5&fontSizePx=18&widthPx=720")
    print(res.status_code, res.text)