ハンドルからYouTubeのチャンネルIDを取得する方法（逆方向も）

cURL

curl -s "https://www.googleapis.com/youtube/v3/channels?part=id&forHandle=@GoogleDevelopers&key=$YOUTUBE_API_KEY"

Node.js

const API = "https://www.googleapis.com/youtube/v3/channels";
async function listChannels(params) {
  const key = process.env.YOUTUBE_API_KEY;
  if (!key) throw new Error("Set YOUTUBE_API_KEY");
  const url = new URL(API);
  url.search = new URLSearchParams({ ...params, key }).toString();
  const res = await fetch(url, { signal: AbortSignal.timeout(10_000) });
  const data = await res.json();
  if (!res.ok) {
    const reason = data.error?.errors?.[0]?.reason;
    if (reason === "channelNotFound") return [];
    throw new Error(`YouTube API ${res.status} ${reason ?? ""}: ${data.error?.message}`);
  }
  return data.items ?? []; // no match: items is empty or missing
}

/** "@GoogleDevelopers" or "GoogleDevelopers" -> "UC_x5XG1OV2P6uZZ5FSM9Ttw" or null */
export async function channelIdFromHandle(handle) {
  const items = await listChannels({ part: "id", forHandle: handle.trim() });
  return items[0]?.id ?? null;
}

/** Legacy username from a youtube.com/user/<name> URL -> channel ID or null */
export async function channelIdFromUsername(username) {
  const items = await listChannels({ part: "id", forUsername: username.trim() });
  return items[0]?.id ?? null;
}

/** Any number of channel IDs -> Map(id -> { title, customUrl }) */
export async function channelsById(ids) {
  const unique = [...new Set(ids)];
  const found = new Map();
  for (let i = 0; i < unique.length; i += 50) {
    const batch = unique.slice(i, i + 50);
    const items = await listChannels({ part: "snippet", id: batch.join(","), maxResults: "50" });
    for (const ch of items) {
      found.set(ch.id, { title: ch.snippet.title, customUrl: ch.snippet.customUrl ?? null });
    }
  }
  return found; // IDs missing from the map were not found
}

Python

import os

import requests

API = "https://www.googleapis.com/youtube/v3/channels"


def list_channels(**params):
    key = os.environ.get("YOUTUBE_API_KEY")
    if not key:
        raise RuntimeError("Set YOUTUBE_API_KEY")
    response = requests.get(API, params={**params, "key": key}, timeout=10)
    data = response.json()
    if not response.ok:
        errors = data.get("error", {}).get("errors") or [{}]
        reason = errors[0].get("reason")
        if reason == "channelNotFound":
            return []
        raise RuntimeError(f"YouTube API {response.status_code} {reason}: {data.get('error', {}).get('message')}")
    return data.get("items", [])  # no match: items is empty or missing


def channel_id_from_handle(handle):
    """'@GoogleDevelopers' or 'GoogleDevelopers' -> 'UC_x5XG1OV2P6uZZ5FSM9Ttw' or None"""
    items = list_channels(part="id", forHandle=handle.strip())
    return items[0]["id"] if items else None


def channel_id_from_username(username):
    """Legacy username from a youtube.com/user/<name> URL -> channel ID or None"""
    items = list_channels(part="id", forUsername=username.strip())
    return items[0]["id"] if items else None


def channels_by_id(ids):
    """Any number of channel IDs -> {id: {"title", "customUrl"}}; missing IDs were not found"""
    unique = list(dict.fromkeys(ids))
    found = {}
    for i in range(0, len(unique), 50):
        batch = unique[i:i + 50]
        for ch in list_channels(part="snippet", id=",".join(batch), maxResults=50):
            found[ch["id"]] = {
                "title": ch["snippet"]["title"],
                "customUrl": ch["snippet"].get("customUrl"),
            }
    return found

Node.jsのキャッシュ

import { channelIdFromHandle } from "./youtube.mjs";

const TTL_MS = 7 * 24 * 60 * 60 * 1000; // refresh well inside YouTube's 30-day limit
const cache = new Map(); // lowercase handle -> { id, at }

export async function cachedChannelId(handle) {
  const key = handle.trim().replace(/^@/, "").toLowerCase();
  const hit = cache.get(key);
  if (hit && Date.now() - hit.at < TTL_MS) return hit.id;
  const id = await channelIdFromHandle(handle);
  cache.set(key, { id, at: Date.now() }); // caches misses (null) too
  return id;
}

Node.js

// Unofficial fallback: reads the public channel page. Fragile, prefer the API.
export async function channelIdFromPage(handle) {
  const url = `https://www.youtube.com/@${encodeURIComponent(handle.replace(/^@/, ""))}`;
  const res = await fetch(url, {
    headers: { "Accept-Language": "en-US" },
    signal: AbortSignal.timeout(10_000),
  });
  if (!res.ok) return null;
  const html = await res.text();
  const match = html.match(/<link rel="canonical" href="https:\/\/www\.youtube\.com\/channel\/(UC[A-Za-z0-9_-]{22})"/);
  return match?.[1] ?? null;
}

Python

import re
from urllib.parse import quote

import requests

CANONICAL = re.compile(r'<link rel="canonical" href="https://www\.youtube\.com/channel/(UC[A-Za-z0-9_-]{22})"')


def channel_id_from_page(handle):
    """Unofficial fallback: reads the public channel page. Fragile, prefer the API."""
    url = "https://www.youtube.com/@" + quote(handle.lstrip("@"), safe="._-")
    response = requests.get(url, headers={"Accept-Language": "en-US"}, timeout=10)
    if not response.ok:
        return None
    match = CANONICAL.search(response.text)
    return match.group(1) if match else None