We're calling on all EU-based Mozillians with iOS or iPadOS devices to help us monitor Apple’s new browser choice screens. Join the effort to hold Big Tech to account!

This site will have limited functionality while we undergo maintenance to improve your experience. If an article doesn't solve your issue and you want to ask a question, we have our support community waiting to help you at @FirefoxSupport on Twitter and/r/firefox on Reddit.

Search Support

Avoid support scams. We will never ask you to call or text a phone number or share personal information. Please report suspicious activity using the “Report Abuse” option.

Learn More

Lolu chungechunge lwabekwa kunqolobane. Uyacelwa ubuze umbuzo omusha uma udinga usizo.

When I added new themes the old themes disappear, why?

  • 1 baphendule
  • 1 inale nkinga
  • 16 views
  • Igcine ukuphendulwa ngu cor-el

more options

I have had themes disappear when adding new themes. I counted the number of themes and counted (including the default one) 31 themes. Is 30 the maximum additional themes you can add? Can I increase this number? Are the deleted themes stored somewhere?

I have had themes disappear when adding new themes. I counted the number of themes and counted (including the default one) 31 themes. Is 30 the maximum additional themes you can add? Can I increase this number? Are the deleted themes stored somewhere?

All Replies (1)

more options

Firefox stores data of a maximum number of Personas (DEFAULT_MAX_USED_THEMES_COUNT=30)

If you install more Personas then Firefox will remove other Personas to make room for the new Persona, so it is best to keep a list or bookmark the site of your favorite Personas.

You can override this maximum by creating an Integer pref with the name lightweightThemes.maxUsedThemes and set its value accordingly.

The data of all installed Personas and its background color and text color are stored in the lightweightThemes.usedThemes pref in JSON object format ({"id":"#","name":"xxx",...}). The first entry of this pref is the currently selected Persona.


  • resource://gre/modules/LightweightThemeManager.jsm
const DEFAULT_MAX_USED_THEMES_COUNT = 30;

this.__defineGetter__("_maxUsedThemes", function maxUsedThemesGetter() {
  delete this._maxUsedThemes;
  try {
    this._maxUsedThemes = _prefs.getIntPref("maxUsedThemes");
  }
  catch (e) {
    this._maxUsedThemes = DEFAULT_MAX_USED_THEMES_COUNT;
  }
  return this._maxUsedThemes;
});