isbot 🤖/👨‍🦰

Identify bots, crawlers, and spiders using the user agent string.

Usage

Install

npm i isbot

Straightforward usage

import { isbot } from "isbot";

// Request
isbot(request.headers.get("User-Agent"));

// Nodejs HTTP
isbot(request.getHeader("User-Agent"));

// ExpressJS
isbot(req.get("user-agent"));

// Browser
isbot(navigator.userAgent);

// User Agent string
isbot(
  "Mozilla/5.0 (iPhone; CPU iPhone OS 6_0 like Mac OS X) AppleWebKit/536.26 (KHTML, like Gecko) Version/6.0 Mobile/10A5376e Safari/8536.25 (compatible; Googlebot/2.1; +http://www.google.com/bot.html)",
); // true

isbot(
  "Mozilla/5.0 (Windows NT 6.1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/41.0.2228.0 Safari/537.36",
); // false

Use JSDeliver CDN you can import to the browser directly

See specific versions and instructions https://www.jsdelivr.com/package/npm/isbot

ESM

<script type="module">
  import { isbot } from "https://cdn.jsdelivr.net/npm/isbot@5/+esm";
  isbot(navigator.userAgent);
</script>

UMD

<script src="https://cdn.jsdelivr.net/npm/isbot@5"></script>
<script>
  // isbot is now global
  isbot(navigator.userAgent);
</script>

All named imports

import	Type	Description
isbot	(string?): boolean	Check if the user agent is a bot
isbotNaive	(string?): boolean	Check if the user agent is a bot using a naive pattern (less accurate)
getPattern	(): RegExp	The regular expression used to identify bots
list	string[]	List of all individual pattern parts
isbotMatch	(string?): string \| null	The substring matched by the regular expression
isbotMatches	(string?): string[]	All substrings matched by the regular expression
isbotPattern	(string?): string \| null	The regular expression used to identify bot substring in the user agent
isbotPatterns	(string?): string[]	All regular expressions used to identify bot substrings in the user agent
createIsbot	(RegExp): (string?): boolean	Create a custom isbot function
createIsbotFromList	(string[]): (string?): boolean	Create a custom isbot function from a list of string representation patterns

Example usages of helper functions

Create a custom isbot that does not consider Chrome Lighthouse user agent as bots.

import { createIsbotFromList, isbotMatches, list } from "isbot";

const ChromeLighthouseUserAgentStrings: string[] = [
  "mozilla/5.0 (macintosh; intel mac os x 10_15_7) applewebkit/537.36 (khtml, like gecko) chrome/94.0.4590.2 safari/537.36 chrome-lighthouse",
  "mozilla/5.0 (linux; android 7.0; moto g (4)) applewebkit/537.36 (khtml, like gecko) chrome/94.0.4590.2 mobile safari/537.36 chrome-lighthouse",
];
const patternsToRemove = new Set<string>(
  ChromeLighthouseUserAgentStrings.map(isbotMatches).flat(),
);
const isbot: (ua: string) => boolean = createIsbotFromList(
  list.filter(
    (record: string): boolean => patternsToRemove.has(record) === false,
  ),
);

Create a custom isbot that considers another pattern as a bot, which is not included in the package originally.

import { createIsbotFromList, list } from "isbot";

const isbot = createIsbotFromList(list.concat("shmulik"));

Definitions

Bot. Autonomous program imitating or replacing some aspect of a human behaviour, performing repetitive tasks much faster than human users could.
Good bot. Automated programs who visit websites in order to collect useful information. Web crawlers, site scrapers, stress testers, preview builders and other programs are welcomed on most websites because they serve purposes of mutual benefits.
Bad bot. Programs which are designed to perform malicious actions, ultimately hurting businesses. Testing credential databases, DDoS attacks, spam bots.

Clarifications

What does "isbot" do?

This package aims to identify "Good bots". Those who voluntarily identify themselves by setting a unique, preferably descriptive, user agent, usually by setting a dedicated request header.

What doesn't "isbot" do?

It does not try to recognise malicious bots or programs disguising themselves as real users.

Why would I want to identify good bots?

Recognising good bots such as web crawlers is useful for multiple purposes. Although it is not recommended to serve different content to web crawlers like Googlebot, you can still elect to

Flag pageviews to consider with business analysis.
Prefer to serve cached content and relieve service load.
Omit third party solutions' code (tags, pixels) and reduce costs.

It is not recommended to whitelist requests for any reason based on user agent header only. Instead, other methods of identification can be added such as reverse dns lookup.

How `isbot` maintains accuracy

isbot is an asset when it can most accurately identify bots by the user agent string. It uses expansive and regularly updated lists of user agent strings to create a regular expression that matches bots and only bots.

Fallback

The pattern uses lookbehind methods which are not supported in all environments. A fallback is provided for environments that do not support lookbehind. The fallback is less accurate. The test suite includes a percentage of false positives and false negatives which is deemed acceptable for the fallback: 1% false positive and 75% bot coverage.