Scrapfly Anti-bot Detector

See how a website defends itself against bots: which anti-bot system, which captcha, which fingerprinting scripts, and how sure each match is.

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Scrapfly Anti-bot Detector is a free Chrome extension that shows how a website protects itself from automated traffic. Browse as you normally would: the number on the toolbar icon tells you how many protections the page uses, and the popup lists each one with its confidence, its difficulty and the signals that gave it away.

It recognizes 85 technologies out of the box: 42 anti-bot systems, 22 CAPTCHAs and 21 browser fingerprinting techniques. Every detector is a plain JSON file that you can read, change or extend, and new rules ship with each release of this repository, so Rules → Update can install them before Chrome updates the extension itself.

We built it at Scrapfly because every scraping project starts with the same question: what is protecting this page? It is just as useful for checking how your own site's bot protection looks from the outside, or for security research.

Contents

• Screenshots
• Install
• How it works
• What it detects
• A tour of the popup
• Integrations
• Privacy and permissions
• Development
• Writing a detector
• Contributing
• License

Screenshots

Click an image to see it full size.

Install

Chrome Web Store

The simplest option: install it from the Chrome Web Store. Chrome keeps it up to date for you.

From a release

Each version on the Releases page has a ready-to-load zip attached.

1. Download the zip and extract it into a new folder.
2. Open chrome://extensions and turn on Developer mode (top right).
3. Click Load unpacked and choose that folder.

From source

There is no build step. Clone the repository and load the folder as it is:

git clone https://github.com/scrapfly/Antibot-Detector.git

Then follow steps 2 and 3 above, choosing the cloned folder. After editing a file, press the reload button on the extension's card in chrome://extensions and reload the page you are testing.

How it works

When a page loads, the extension gathers what the page reveals about itself and checks it against every enabled detector. Each detector combines up to eight methods:

Method	What it looks at	Example signal
URL	The page address, script sources and every network request	challenges.cloudflare.com/turnstile/v0/api.js
Cookies	Cookies the site sets or sends, HttpOnly ones included	_abck (Akamai), datadome
Headers	Response and request headers	x-kpsdk-ct (Kasada)
Content	The page's HTML and the code of its inline and loaded scripts	KPSDK.configure(
DOM	Elements matched by a CSS selector	.cf-turnstile[data-sitekey]
Window properties	Objects that scripts add to window	grecaptcha.render
JavaScript hooks	Calls to browser APIs commonly used for fingerprinting	HTMLCanvasElement.prototype.toDataURL
Payload	Bodies of POST, PUT and PATCH requests, optionally filtered by URL and method, and the responses of the URLs a rule names	sensor_data (Akamai), "proofofwork":{"required":true (OpenAI Sentinel)

Confidence. Each rule has its own confidence and detectors define combinations of rules that score higher together. A script that only mentions a vendor's name scores 5–10%; a signal only that vendor's product produces (its own script host, its own cookie, its challenge endpoint) is proof and scores 100% on its own, and so does a vendor's complete integration (its script together with its cookie, widget frame or challenge request). Shared or generic signals stay at 15–90%. The score shown for each detector is its strongest single rule or combination. The page also gets a difficulty rating (Low, Medium or High), which sets the color of the toolbar badge.

Fingerprinting. The API hooks are in place before the page's own scripts run, and they also cover same-origin iframes, where fingerprinting code often hides. By default they watch for at least 4 seconds, then until the page has been quiet for 2 seconds, and for 8 seconds at most.

Caching. A result is reused for 7 days by default, so revisiting a page shows it straight away. You can change the duration, and whether a result is shared by the whole domain, by pages with the same path or only by the exact URL, in Settings → Detection. Clear Cache on the Detection tab forgets the stored result, so the page is scanned again the next time it loads.

What it detects

The lists below are the detectors that ship with the extension. You can switch any of them off, edit them or add your own in the Rules tab.

Akamai Bot Manager · Alibaba Cloud WAF · Amazon Bot Protection · Anubis · AWS WAF · Azure Front Door · Castle · Cheq · Cloudflare Bot Management · Cloudflare Waiting Room · DataDome · DDoS-Guard · DeepSeek PoW · F5 BIG-IP ASM · Fastly Bot Management · FingerprintJS · Forter · Google BotGuard · HUMAN (PerimeterX) · Hunt · Incapsula (Imperva) · iovation (TransUnion TruValidate) · Jiasule (Chuangyu Shield) · Kasada · Kount · Meetrics Check · Netacea · Ocule · OpenAI Sentinel · Queue-it · Radware Bot Manager · Reblaze · Riskified · Ruishu · SEON · Shape Security · Sift · Sucuri WAF · ThreatMetrix · Vercel Firewall · Wordfence · Yundun Cloud WAF

AliExpress CAPTCHA · Aliyun Captcha 2.0 · ALTCHA · Basilisk Captcha · Binance Captcha · Cap · Captcha.eu · Capy Puzzle Captcha · Cloudflare Turnstile · Dingxiang Captcha · Friendly Captcha · FunCaptcha (Arkose Labs) · GeeTest · Google reCAPTCHA · hCaptcha · Lemin Cropped Captcha · MTCaptcha · NetEase Yidun · Prosopo Procaptcha · QCloud Captcha · Shumei Captcha · Yandex SmartCaptcha

Audio · Battery API · Canvas · Clipboard API · Crypto · CSS · Device Orientation · Font · Gamepads API · Geolocation · Hardware · IndexedDB · Media · Navigator · Performance · Screen · Timezone/Intl · USB API · Web Storage · WebGL · WebRTC

A tour of the popup

Detection

The protections found on the current page, each with its confidence, its difficulty and the methods that matched. Click a card to see the exact signals behind it. Hovering the toolbar icon names them without opening the popup, and Alt+Shift+S (Control+Shift+S on Mac; change it in the browser's shortcut settings) scans the current page again. The buttons at the top let you:

• Upload detections to get a shareable link (dpaste.com by default; see Share links)
• Clear Cache, so the page is scanned again on its next load
• Copy, a menu: the same summary that the upload shares, a Markdown table for a ticket or a chat, or JSON (none of them holds cookie or header values)
• Block this domain, so the extension stops scanning it

History

Every page that had detections, with its protections and difficulty. Search it, open an entry for its details, import a JSON export, and export it as JSON, CSV, plain text or Markdown, choosing the protections, period, site and pinned pages first. Pin an entry (it is kept when History is cleaned up), add a note, open the page, scan it again now or copy it as Markdown from its ⋯ menu. Clicking a "Protections changed" notification opens that page. A Changed badge marks a page whose protections differ from its last scan. Settings → Data → Open statistics opens a statistics page (activity, protections, domains, confidence, signals, combinations, rules and Advanced tools) computed locally from your history.

Rules

All detectors, built-in and your own. Turn each one on or off, open the editor to change its patterns, or add a detector of your own with Add. The More actions menu (⋯) imports and exports detectors as JSON. Every pattern has its own settings: where to look (the page, scripts or all requests; request or response for cookies and headers), whether it is a regular expression, whole word or case sensitive, and its confidence. The editor also handles combinations and the detector's icon, and a regex helper lets you test a pattern against sample text. Check against History shows on how many of your saved pages each pattern and combination matches, and Test on this page runs the rule as it is now (unsaved edits included) on the page the popup is open on: what each cookie, URL, content and DOM pattern finds there, and whether the rule and its combinations match. Header, JS hook, window and payload patterns can only be answered by a real scan, so the test lists them as such instead of as "no match". Nothing is saved or sent.

Update downloads the official detectors of this repository's latest release. A built-in detector you have edited is never replaced without asking: you choose between your version and the new one. If you delete a built-in detector, Restore official detectors in the same menu brings it back. Detector updates can also run on a schedule (Settings → General).

Advanced

Hands-on tools for the protections a page uses. A protection gets its tools when it is detected above 50% confidence; you can change that limit in Settings → Detection → Advanced tools. When nothing on the page qualifies, the tab says so, gives that minimum (or names the protection found below it) and shows the 25 supported protections.

Protection	Tools
Akamai Bot Manager	Check Cookies · Analyze Scripts · Extract Sensor Information · Start Capturing
AWS WAF	Check Cookies · Analyze Scripts
Cloudflare Bot Management	Check Cookies · Analyze Scripts
Cloudflare Turnstile	Extract SiteKey · Analyze Scripts
DataDome	Check Cookies · Analyze Scripts
FunCaptcha (Arkose Labs)	Extract Public Key · Analyze Scripts · Start Capturing
GeeTest	Check Version · Analyze Scripts
Google reCAPTCHA	Obtain Selector · Extract SiteKey · reCAPTCHA callback · Start Capturing
hCaptcha	Extract SiteKey · Check Version · Analyze Scripts · Start Capturing
Incapsula (Imperva)	Check Cookies · Analyze Scripts · Start Capturing
Shape Security	Check Version · Check Cookies · Analyze Scripts · Start Capturing
Aliyun Captcha 2.0, Captcha.eu, Capy Puzzle Captcha, Dingxiang Captcha, Friendly Captcha, MTCaptcha, NetEase Yidun, Prosopo Procaptcha, QCloud Captcha, Shumei Captcha, Yandex SmartCaptcha	Extract SiteKey · Analyze Scripts
AliExpress CAPTCHA, Basilisk Captcha, Binance Captcha	Analyze Scripts

Results and captures are kept for 30 minutes in Advanced → History, where you can filter them by site, vendor and tool, open them again and export them.

Settings

• General: interface language (22 languages, following your browser by default), theme (Dark, Light or System), notifications, debug mode, scheduled detector updates, and the colors of the badge, categories and tags.

• Detection: cache duration and scope, the order of categories in the results, the Advanced tools confidence limit, which sites are scanned (every site except the ones you skip, or only the sites you choose), JS API events, webhooks and share links.

• History: what to record (pause History, skip private windows, ignored sites, minimum confidence, skip fingerprint-only pages), how many entries to keep (up to 10,000; 0 keeps the newest 1,000), deleting entries after a number of days or when the browser closes, skipping or updating repeated scans, notifications when a page's protections change, the default export format, a storage meter with its warning, and an automatic backup to your Downloads folder.

  History is limited to about 6 MB, or 12 or 25 MB if you choose a larger size in Settings → History; when it is full the oldest unpinned entries are removed, and Settings → History says how many. Pages with a hard protection, or one you name, can pin themselves (up to 50), fingerprint-only pages can be deleted after a number of days of their own, and up to 10 pinned pages can be watched: scanned again every day or week in a background tab, with the entry marked Changed when its protections change (each check is a real visit with your cookies).

• Data: open the statistics page; see how much space each part of the extension uses and clear the detection cache, tool captures, logs or History; back up settings, your own rules and History in one file and restore it; export or import your settings and your history; apply the Privacy or Developer preset or reset every setting; copy a diagnostics summary for a bug report (no sites, addresses or keys).

Integrations

JavaScript events

The extension dispatches events on the page's window, so your own scripts (or a test harness) can react to its results:

Event	When
scrapfly:ready	The extension has loaded on the page
scrapfly:onStart	A scan starts (no cached result, or a manual scan)
scrapfly:onProgress	One detection method has finished
scrapfly:onHooksComplete	The JavaScript hooks stopped watching
scrapfly:onWindowPropsComplete	The window property checks finished
scrapfly:onDetection	The results are ready, including results served from the cache
scrapfly:onError	The scan failed

const on = (ev, cb) =>
  addEventListener(`scrapfly:${ev}`, cb);

on('onDetection', (e) => {
  const { url, detections } = e.detail;
  console.log(url, detections);
});

Because these events reach the page itself, any website you visit can listen for them and learn that the extension is installed. They are off by default; turn them on in Settings → Detection → JS API Events.

Webhooks

When a scan finds protections, the extension can send the results to your own endpoint. Choose the HTTP method, add headers and write the body as a template with variables such as <SITEURL>, <HOSTNAME>, <TITLE>, <DETECTIONS>, <DETECTION_COUNT>, <DETECTION_NAMES> (the protections with their confidence, on one line), <CATEGORIES> and <TIMESTAMP>. Start from a preset (Slack, Mattermost or Google Chat, Discord, or a plain text line) fills in the Content-Type and a ready-made chat message. Webhooks only go to HTTPS addresses on public hosts, are off by default, and include a Test button. Set them up in Settings → Detection → Webhook Integration.

Recent deliveries and retries. Settings → Detection → Webhook lists the last 20 attempts (the page, the status, how long it took; never an address, header or payload). A delivery that fails can be sent again with Retry, and with Retry failed deliveries on (the default) the extension also retries by itself after 1, 5 and 15 minutes when there was no answer or the server answered 408, 425, 429 or 5xx; a refusal such as 401, 403 or 404 waits for your Retry. To do that, the page data of a failed delivery is kept in memory for an hour (at most 20), never on disk, and gone when the browser closes; a retry builds the request again from your current webhook settings, so a corrected address or secret is used and no header or secret is stored with it.

Signing. Set a signing secret (or press Generate, then Copy it to your server) and each request with a body is signed the way Scrapfly's own webhooks are: X-Scrapfly-Webhook-Signature holds the HMAC-SHA256 of the raw body as uppercase hex, keyed with the secret exactly as written (its UTF-8 bytes; a generated secret is not decoded from hex), and X-Scrapfly-Webhook-Signature-Lowercase the same value in lowercase. Check it against the raw body before parsing it, with a constant-time comparison. GET, HEAD and multipart/form-data requests are not signed, and the URL is never part of the signature. There is no timestamp header; the default template sends <TIMESTAMP> in the body, so your server can refuse stale requests. The secret stays in this browser: exports, backups and diagnostics leave it out, and Reset keeps it unless you also remove the connections.

// Node.js, with the raw body as a Buffer (for example express.raw({ type: '*/*' }))
const crypto = require('node:crypto');
function isFromExtension(rawBody, signatureHeader, secret) {
  const expected = Buffer.from(crypto.createHmac('sha256', secret).update(rawBody).digest('hex'));
  const received = Buffer.from(String(signatureHeader || '').toLowerCase());
  return received.length === expected.length && crypto.timingSafeEqual(received, expected);
}
// isFromExtension(req.body, req.get('X-Scrapfly-Webhook-Signature'), process.env.WEBHOOK_SECRET)

import hashlib, hmac
def is_from_extension(raw_body: bytes, signature_header: str, secret: str) -> bool:
    expected = hmac.new(secret.encode(), raw_body, hashlib.sha256).hexdigest()
    return hmac.compare_digest(expected, (signature_header or "").lower())

Share links

Upload detections on the Detection tab publishes a summary of the page's results, copies the link and opens it in a new tab. The summary contains the page address without its query string or fragment, each protection's name, category and confidence, and which methods matched; never cookie or header values. Choose where it goes, and when it is deleted where the service allows it, in Settings → Detection → Share uploads: dpaste.com (the default), dpaste.org, paste.rs, Pastebin with your API key, a secret GitHub Gist with your token, or your own server.

Privacy and permissions

Detection runs entirely in your browser. There are no accounts and no analytics, and nothing about the pages you visit is sent to Scrapfly. The extension does make a few network requests, and you should know what they are:

• Script contents. To read a script's code, it downloads the page's scripts and stylesheets again, through the browser cache and without cookies.
• Detector updates. Update, or the optional schedule, asks api.github.com for this repository's latest release, then reads that release's detector files from raw.githubusercontent.com.
• Site icons. History and other lists show a site's own favicon, or ask Google's favicon service when the site has none.
• Language flags. The language picker in Settings loads its flags from flagcdn.com.
• Only when you use them: webhooks and share links, as described above. JS API events never leave the browser, but the page you visit can read them (see JavaScript events).

Permission	Used for
Access to all sites (http://*/*, https://*/*)	Scanning whatever page you open
storage	Settings, detectors, history and cached results
tabs, activeTab	Knowing which page the popup is about, and opening pages such as the statistics view
scripting	Running the Advanced tools inside the page
webRequest	Reading request URLs, headers and request bodies for detection and captures
webNavigation	Knowing when a page or frame has finished loading
cookies	Reading cookies, including HttpOnly ones; some Analyze tools reset a protection cookie before reloading the page
notifications	Status messages from the capture tools
downloads	Saving exported files
alarms	Scheduled detector updates and the clean-up of old history and cached results
unlimitedStorage	Lets History take more than the 10 MB browser quota when you choose 12 or 25 MB in Settings → History; History stays at 6 MB unless you choose more

Development

You need Chrome (or Chromium) to run the extension and Node.js 20 or newer for the checks. There are no runtime dependencies and no bundler: the files in this repository are the extension.

manifest.json            Manifest V3 definition
background.js            Service worker entry point, loads background/
background/              Detection lifecycle, message handlers, cache, badge
content.js               Content script (isolated world)
content-main-world.js    Page-world hooks, installed before the page's scripts
modules/                 Detection engine, core services, UI helpers, styles
popup.html, popup.js     The popup
sections/                One folder per popup tab (detection, history, rules, advanced), plus settings (the Settings modal) and stats (the Statistics page)
detectors/               Detector rules (JSON), index.json, icons and rule translations
_locales/                Translations for the 22 languages
utils/                   Shared helpers
scripts/                 Repository checks and browser tests
test/                    Unit tests (node:test)

Checks

npm run verify            # everything below, as CI runs it
npm run check:syntax      # node --check on every JavaScript file
npm run check:structure   # HTML tag balance, JSON validity, modal markup
npm run check:locale      # every language has exactly the keys of English
npm run check:locale-quality  # placeholders, code, script, fonts and Web Store limits of every translation
npm run check:rule-i18n   # every rule text is translated in detectors/i18n/
npm test                  # unit tests on Node's built-in test runner

The browser tests load the real extension in Chromium. They are not part of verify, and they need Playwright. npm run e2e:setup prepares it once, outside the repository (in ~/.cache/antibot-e2e): it installs Playwright, finds a Chromium that matches it (linking another cached revision under the expected name rather than downloading again), starts Chromium through a wrapper that adds --disable-gpu on Windows Subsystem for Linux, where it otherwise draws no frames, and checks that a frame is drawn. By hand, npm i --no-save playwright && npx playwright install chromium also works.

npm run e2e:all runs every suite below one at a time, with a time limit each, a log for each and a summary (-- --only history,data, --skip languages, --bail, --timeout <minutes>, --repo <another checkout>). Run nothing else heavy meanwhile: the suites are timing-sensitive, and the unit tests running beside one have made scenarios fail for no reason of their own.

npm run e2e:methods    # every detection method, from URL to JavaScript hooks
npm run e2e:settings   # every per-pattern setting: scopes, regex, whole word, case
npm run e2e:editor     # the rule editor saves settings and keeps every field
npm run e2e:updater    # Rules → Update against a local stand-in for GitHub
npm run e2e:data       # Settings → Data: storage and Clear, backup and restore, presets and reset, diagnostics
npm run e2e:scope      # Settings → Detection → Sites to scan: skipped sites, chosen sites, the paused card
npm run e2e:webhook    # Settings → Detection → Webhook: filters, cache, failures, Recent deliveries, Test, Clear, signing
npm run e2e:hooks      # Settings → Detection → Sites without JS hooks: hooks on and off, switching, the popup note, the cache
npm run e2e:rule-texts  # Rules editor texts in Spanish: one plain box, replaced when changed, untouched when left alone
npm run e2e:quickwins  # 3.0.3: toolbar hover text, the copy menu, the rescan shortcut, notification clicks, History open and rescan, Duplicate rule, Markdown exports
npm run e2e:languages  # every language through the real popup, settings and statistics pages
npm run e2e:controls   # every checkbox, radio and dropdown on screen is drawn by the interface, none is the browser's default look
npm run e2e:live       # detectors against the real sites in scripts/live-sites.json

e2e:live needs a network connection, and live sites change over time, so a failure there is something to look into rather than proof that a rule is wrong.

CI runs npm run verify on every push and pull request. To run it locally before each push, enable the repository's hook once:

git config core.hooksPath .githooks

Adding a language

A language is a folder of translations plus a few registrations, and the checks fail until all of them are done:

1. Create _locales/<code>/messages.json with every key of _locales/en/messages.json ({ "key": { "message": "..." } }, {0} placeholders and code in `backticks` unchanged), using a code Chrome accepts (pt_BR, zh_TW, uk...).
2. Create detectors/i18n/<code>.json with the translation of every rule text (node scripts/check-rule-i18n.js --missing lists them). Cookie, header and path names stay as written.
3. Add the language to the picker (sections/settings/settings-ui-language.js, in its own name), its flag (utils/url-utils.js), the lists in modules/core/rule-i18n.js, modules/detection/rules/update-manager.js, modules/settings/settings-store.js and sections/rules/rules-translations-ui.js. test/locale-registry.test.js names the one you forgot.
4. Write its Chrome Web Store listing: store/listing/<code>.txt (the description, translated from en.txt), store/captions/<code>.json (the copy printed on the images) and the five images from node scripts/generate-store-screenshots.js --lang <code>. npm run check:store-listing and npm run check:store-images name what is missing or wrong; store/README.md has the rules and the commands.
5. Run npm run verify, then npm run e2e:languages -- --only <code> --shots /tmp/shots and look at the screenshots: it reports text still in English, raw {0} placeholders and labels cut off.

A new script needs its IBM Plex family too (Thai ships IBMPlexSansThai-*.woff2 in assets/fonts/, declared in modules/styles/common.css and listed in test/font-family.test.js): otherwise the system's font draws it, and npm run check:locale-quality lists the characters involved.

Writing a detector

A detector is one JSON file. This is detectors/antibot/detect-datadome.json with four of its rules and one of its combinations:

{
  "id": "detect-datadome",
  "name": "DataDome",
  "author": "Scrapfly",
  "enabled": true,
  "category": "Anti-Bot",
  "difficulty": "Medium",
  "lastUpdated": "2026-10-05",
  "version": "2.0.0",
  "minExtensionVersion": "2.8",
  "website": "https://datadome.co/",
  "icon": "datadome_official.png",
  "description": "Real-time bot protection with machine learning-based detection",
  "detection": {
    "cookie": [
      {
        "id": "datadome-cookie",
        "name": "^datadome$",
        "nameRegex": true,
        "confidence": 85,
        "description": "DataDome session cookie",
        "nameScope": "all",
        "valueScope": "all"
      }
    ],
    "url": [
      {
        "id": "datadome-tag",
        "confidence": 75,
        "description": "Official DataDome JavaScript tag or its collection endpoint",
        "text": "^https://(?:js|api-js)\\.datadome\\.co/(?:tags\\.js|js/)",
        "textRegex": true,
        "textCaseSensitive": false,
        "textScope": "all"
      }
    ],
    "content": [
      {
        "id": "ddjskey-reference",
        "confidence": 25,
        "description": "Integration snippet setting window.ddjskey",
        "text": "ddjskey",
        "textWholeWord": true,
        "textCaseSensitive": true,
        "scope": "scripts",
        "checkScripts": true
      }
    ],
    "window": [
      {
        "id": "ddjskey-variable",
        "path": "ddjskey",
        "condition": "typeof string",
        "confidence": 60,
        "description": "DataDome JS key set by the integration snippet"
      }
    ]
  },
  "combinations": [
    {
      "id": "datadome-tag-session",
      "name": "DataDome tag with its session cookie",
      "confidence": 95,
      "when": {
        "all": [
          { "any": [{ "pattern": "datadome-tag" }, { "pattern": "ddjskey-variable" }, { "pattern": "ddjskey-reference" }] },
          { "pattern": "datadome-cookie" }
        ]
      }
    }
  ]
}

On their own, the cookie scores 85% and the tag 75%. The combination raises DataDome to 95% when the cookie appears together with the tag, the ddjskey variable or a script that sets it.

To add one:

1. Create detectors/<category>/detect-<name>.json, where the category is antibot, captcha or fingerprint.
2. Add its id to the matching list in detectors/index.json.
3. Put its logo in detectors/icons/, or use custom.png (the Scrapfly logo).
4. Translate each rule description and combination name in every detectors/i18n/<locale>.json. node scripts/check-rule-i18n.js --missing lists the texts still missing.
5. For anti-bot and CAPTCHA detectors, add a real example of each rule's signal to test/fixtures/antibot-confidence.json or test/fixtures/captcha-confidence.json. Then run npm run verify.
6. Check it on a live page by adding the site to scripts/live-sites.json and running npm run e2e:live.

A few things to keep in mind:

• 100% means proof. A rule scores 100% on its own only when no other product can produce its signal: a request to a host the vendor owns for that product, a header or cookie with a vendor-coined name (a short name such as _px3 also checks the value's shape), the vendor endpoint's own request or response body, or a token only the vendor injects (Akamai's _abck cookie, Cloudflare's /cdn-cgi/challenge-platform/ requests, hCaptcha's api.js). Markup, source text, window globals and anything shared with another product never are: an anti-bot rule of that kind scores at most 90% and a CAPTCHA rule at most 60%. A combination reaches 100% only at a detector's top tier, where every branch is made of that vendor's own signals; the other tiers stay at or below 95%. A rule marked "standalone": false only counts inside a combination. The tests check these limits (test/antibot-confidence.test.js, test/captcha-confidence.test.js).
• Raise version whenever you change a detector's rules, or Rules → Update will not offer the new version.
• Mind minExtensionVersion. Rules → Update serves the detectors of the latest release to every installed copy of the extension (2.8.2 and older read the main branch instead), so a detector that relies on newer engine features must declare the oldest extension version that understands it. Older copies then skip it, and 2.8.3 and newer list it as waiting for an extension update.

Contributing

Bug reports, detector improvements and new detectors are all welcome. If a detector misses a site or flags one it shouldn't, please open an issue with the page address and what you expected to see.

For pull requests:

• npm run verify must pass.
• Record user-visible changes in CHANGELOG.md under [Unreleased]: one short line that describes what changes for the person using the extension.
• New interface text goes into every folder of _locales/; npm run check:locale checks it.
• There is no bundler, so a new script file has to be added, after the files it depends on, everywhere it is loaded: background.js, popup.html or the content_scripts list in manifest.json. test/load-order.test.js checks the order.

License

Released under the Non-Profit Open Software License 3.0 (NPOSL-3.0).

Copyright © 2026 Scrapfly.