From MozillaZine Knowledge Base



Spell checking in Mozilla can cause extremely high processor usage in large documents, as the entire document is processed. In order to avoid this, the spell checker now only processes text until it reaches an upper bound of misspelled words. If the number of misspelled words decreases to a value below the upper bound (i.e., the user corrects them), the spell checker will continue. This preference controls the upper bound of misspellings.

Possible values and their effects

This integer preference determines the maximum number of misspelled words the spell checker can encounter before it stops checking. (Default is 500)


  • This functionality is not yet available in any officially released versions of Mozilla Firefox. The browser must be built with --enable-extensions=default,spellcheck in configure.
  • layout.spellcheckDefault must be set 1 or 2 for this preference to have an effect in Firefox or SeaMonkey Browser.
  • mail.spellcheck.inline must be true for this to have an effect in Thunderbird or SeaMonkey Mail.

First checked in

Has an effect in

  • Mozilla Firefox (Trunk builds after 2006-02-27)
  • Mozilla Thunderbird (Trunk builds after 2006-02-27)
  • SeaMonkey (Trunk builds after 2006-02-27)

Related bugs

Related preferences