Custom Rules

Custom rules let you cover sites the built-in rules miss, or validate a new rule locally before contributing it upstream.

Form Fields

Field	Required	Description
Tech name	Yes	The name shown in the popup, e.g., MyCMS
Category		Pick a built-in category (23 available) or type your own. Defaults to "Other Libraries". The select supports free input.
Kind label		A note for yourself, e.g., Enterprise CMS, Third-party Payment. Appears as an evidence prefix. Can be empty.
Confidence		High / Medium / Low. Defaults to Medium.
Match mode		Keyword / Regex. Defaults to Regex.
Website / repo URL		Must be http:// or https://. When set, the tech name in the popup becomes a clickable link.

Below those fields are four areas:

• Match scope: determines which data sources the patterns / selectors / globals are tested against

  • Page URL: the current page's address
  • Resource URLs: scripts, stylesheets, iframes loaded by the page
  • DOM / Source: the page's outerHTML
  • Response Headers: main document + API + iframe response headers
  • Dynamic Resources: resources continuously accumulated by the MutationObserver

• Match patterns: one per line. In keyword mode, each line is a literal substring match. In regex mode, each line is a JavaScript regex source (no /.../i wrapper — the i flag is added automatically).

• CSS selectors: one per line, e.g., [data-v-app], #__next. Match scope must include DOM / Source.

• Global variables: one per line, e.g., React, Vue.config, __NEXT_DATA__. A match counts as high confidence.

Adding / Updating

• Add Rule (green primary button): saves the current form as a new rule
• Update current rule: click the edit button on a rule in the list to enter edit mode, make changes, then save

You must click "Save Settings" in the top-right to write the rules to storage.

Saved Rules List

Shown at the bottom of the page. Each entry shows:

• Title: the rule's tech name
• Metadata: category · kind · confidence · match mode · N patterns
• Actions: Edit and Delete buttons (Delete turns red on hover)

Validation

Rules are validated on every add, update, and settings save:

• Name is required
• At least one of patterns / selectors / globals must be non-empty
• At least one match scope must be selected
• URL, if provided, must start with http(s)😕/
• Each pattern (in regex mode) must compile with new RegExp
• Each selector must pass document.createDocumentFragment().querySelector
• Each global must follow the MyCMS or google.maps dot-separated variable name format

Validation failures show a red tooltip listing up to 6 problems.

Example: Simple Keyword Match

Detect ExampleCMS:

Tech name:  ExampleCMS
Category:   CMS / Website Programs
Match mode: Keyword
Patterns:
  examplecms
  X-Generator: ExampleCMS
Scope: [x] Page URL [x] Resource URLs [x] DOM / Source [x] Response Headers

Example: Detect a WordPress Theme

Tech name:  WordPress Theme: oceanwp
Category:   Themes / Templates
Match mode: Keyword
Patterns:
  /wp-content/themes/oceanwp/
Scope: [x] Resource URLs [x] DOM / Source

Example: Detect a Dynamically Loaded Payment SDK

The payment script only loads after the user clicks the payment button, so check Dynamic Resources:

Tech name:  ExamplePay
Category:   Payment Systems
Kind:       Third-party Payment
Match mode: Keyword
Patterns:
  pay.example.com
  examplepay-sdk
Scope: [x] Dynamic Resources

Example: Regex Match for a Versioned Library File

Tech name:  ExampleLib
Category:   Frontend Libraries
Match mode: Regex
Patterns:
  examplelib-[0-9.]+\.min\.js
Scope: [x] Resource URLs [x] Dynamic Resources

Reducing False Positives

• Avoid overly generic keywords like app, main, or login — almost every site has those
• Prefer a full domain pay.example.com over a short string pay
• Prefer a specific path /wp-content/themes/oceanwp/ over just oceanwp
• When in doubt, set confidence to Low — the popup shows a gray pill to signal it's a guess
• After saving a rule, always refresh the target page before reopening the popup; otherwise the cache still reflects the old results