next.js/packages/next/src/shared/lib/router/utils/is-bot.ts

import { HTML_LIMITED_BOT_UA_RE } from './html-bots'

// Bot crawler that will spin up a headless browser and execute JS.
// By default, only googlebots are considered as DOM bots. Blow is where the regex is computed from:
// x-ref: https://developers.google.com/search/docs/crawling-indexing/google-common-crawlers
const HEADLESS_BROWSER_BOT_UA_RE = /google/i

export const HTML_LIMITED_BOT_UA_RE_STRING = HTML_LIMITED_BOT_UA_RE.source

export { HTML_LIMITED_BOT_UA_RE }

function isDomBotUA(userAgent: string) {
  return HEADLESS_BROWSER_BOT_UA_RE.test(userAgent)
}

function isHtmlLimitedBotUA(userAgent: string) {
  return HTML_LIMITED_BOT_UA_RE.test(userAgent)
}

export function isBot(userAgent: string): boolean {
  return isDomBotUA(userAgent) || isHtmlLimitedBotUA(userAgent)
}

export function getBotType(userAgent: string): 'dom' | 'html' | undefined {
  if (isDomBotUA(userAgent)) {
    return 'dom'
  }
  if (isHtmlLimitedBotUA(userAgent)) {
    return 'html'
  }
  return undefined
}