Form Autofill Heuristics

Form Autofill Heuristics module is for detecting the field type based on autocomplete attribute, the regular expressions and the customized logic in each parser.


The pref extensions.formautofill.heuristics.enabled is “true” in default. Set it to “false” could be useful to verify the result of autocomplete attribute.

Dependent APIs

element.getAutocompleteInfo() provides the parsed result of autocomplete attribute which includes the field name and section information defined in autofill spec

Regular Expressions

This section is about how the regular expression is applied during parsing fields. All regular expressions are in heuristicsRegexp.js.

Parser Implementations

The parsers are for detecting the field type more accurately based on the near context of a field. Each parser uses FieldScanner to traverse the interested fields with the result from the regular expressions and adjust each field type when it matches to a grammar.

  • _parsePhoneFields

    • related type: tel, tel-*

  • _parseAddressFields

    • related type: address-line[1-3]

  • _parseCreditCardExpirationDateFields

    • related type: cc-exp, cc-exp-month, cc-exp-year