Bad Eyesight - Thunderbird

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This article was written for Thunderbird but also applies to Mozilla Suite / SeaMonkey (though some menu sequences may differ).

Addons and Tweaks

Many of these solutions only work with HTML messages, or messages that have both a plain text and a HTML version of the same message body ("View -> Message Body As" chooses which one is displayed). They typically don't work with a plain text message because they use CSS and it only effects how markup languages such as HTML is displayed.

  • The Theme font & size changer add-on for Thunderbird changes fonts/font sizes in menus, toolbars etc., but not within a message. That add-on is crippled in Thunderbird 60.* due to it not being updated to deal with changes in the Mozilla Toolkit. Use Theme font & size changer (fixed) instead. Unfortunately there isn't a version that works for version 68 yet.
  • Change the font/font size in messages by using Tools -> Options -> Display -> Fonts -> Advanced, set the "minimum font size" and consider also unchecking "allow messages to use other fonts". If you don't want to change the font size you can set View -> Message Body As > Simple HTML, which removes some display formatting within the message such as font sizes and colors. It may not look as nice, but you can read the small print again.
  • The No small text add-on lets you set a minimum size for all HTML text and switch it on and off with a toolbar button. It supports three preset sizes. Its supposedly compatible with add-ons similar to Firefox's NoSquint add-on.
@namespace url("");

/* */
/* Global UI font - the leading '*' is not a typo */
 * { font-size: 16pt !important; 
     font-family: Verdana !important;  
  • "Control +" (using the auxiliary keypad), "Control Shift +" (using the main keyboard) and View -> Zoom changes the zoom setting (before Thunderbird 24 that changed the font size instead) when reading or writing a message. That setting is not sticky, i.e. when you exit and restart Thunderbird you'll have to do it again. That is why it is typically easier to use an add-on or CSS snippet to have a permanent change. If you can't zoom, try temporarily disabling all add-ons using Safe mode (not to be confused with Windows safe mode) to see if an add-on is the culprit.
  • The Montezooma add-on adds zooming capabilities to the message window. The ImageZoom add-on lets you zoom images.
  • The CustomizeMyBird add-on supports many changes to Thunderbird's appearance. It replaces the NewScrollbars add-on that only let you change the width, color and/or background color of the scroll bar to provide a high contrast scroll bar.

Sending Messages

There isn't much you can do to make a plain text message more easily readable. However, you can change the font and font size and bold the text in a HTML message to make it easier for the recipient to read it. The easiest way to do this is to create a message template and use it to create a new message whenever you send a message to somebody with poor eyesight. If you have any sort of organized data consider putting it in a table.

Use fixed font sizes for sending your messages with caution. In general, you can assume that the recipient will have made adjustment to his or her settings optimum for their needs, thus you may inadvertently override such settings.

Dark Themes

A Dark theme was included (already installed) in version 60. You can select it using Tools -> Add-ons -> Themes.

There are a couple other themes designed for high contrast available at the Thunderbird Add-ons web site.

Monterail Full Dark
Monterail Dark
Metal Lion SeaMonkey
Metal Lion Silver SeaMonkey
TTDeepDark (doesn't support version 60 yet)

Version 60.0 has a bug where you may need to restart Thunderbird several times in order to get it to use a complete theme.

See White on black - Thunderbird for an example of how to use your userContent.css file to display messages in Thunderbird in white text on a black background.

Thunderbird 5.0 and later

Thunderbird 5.0 has Direct2D font rendering enabled by default on Windows platforms which support it (so does Firefox 4.0+ and SeaMonkey 2.1+). This is in addition to the ClearType handling described below. If the fonts remain difficult to read after adjusting the ClearType settings, go into Tools → Options → Advanced → General and click on Config Editor. Switch the gfx.direct2d.disabled setting to "true" by double-clicking on it to disable the D2D feature. You need to restart Thunderbird to see its effect.

If you are using the High Contrast desktop themes on Windows 7 or Vista, hard-wired colors and gradients introduced during the redesign of the "aero" default theme may make reading the menu bar and the toolbar buttons difficult (screendumps). There is a userChrome.css workaround available to increase visibility of the menu and button texts (CSS code, screendump).

Other solutions

Try accessibility features of your operating system, which can be better than what is possible within Thunderbird.

  • Windows users can use the accessibility wizard at Start -> Programs -> Accessories -> Ease of Access or Accessibility.
  • There are free programs such as BigType that will magnify any text near where you are typing using a magnifier window.
  • Try the Windows Classic or a High Contrast theme by selecting the Appearance tab in the Display Properties of Control Panel, and then Color Scheme. On Windows 7, right-click on the desktop and select Personalize from the context menu. (Default and other desktop themes on Windows 7 and Vista employ a "glass" effect with transparency, which may make it hard to recognize text and shapes.)
  • For LCD monitors, use the cleartype tuner powertoy to tune the the text to your eyesight. On Windows 7, right-click on the Desktop and select Personalize from the context menu, then select Display and choose the "Adjust ClearType text" category. If you prefer unsmoothed (crisp) fonts, uncheck "Turn on ClearType" to avoid font smoothing.
  • Dragon Naturally Speaking is speech recognition software, but it also has a text-to-speech option. You might buy something like that to speak what you are reading.

See Also

Forum Links

External Links

Bug reports