From MozillaZine Knowledge Base

To change the text size of web pages, do any of the following

• Firefox 2 and below: View -> Text Size -> Increase / Normal / Decrease

• Firefox 3 and above: View -> Zoom -> Zoom In / Zoom Out / Reset / Zoom Text Only
  • Ctrl+0 (hold the control key and press zero) resets zoom to normal size (Zoom RESET).
  • Ctrl++ (hold the control key and press the plus key) makes the text larger (Zoom IN).
  • Ctrl+- (hold the control key and press the minus key) makes the text smaller. (Zoom OUT)
  • Ctrl+scroll with mouse wheel

These changes will only change text sizes temporarily. "Tools -> Options -> Content -> Fonts & Colors gives you options that will stick.

Note that some web pages may display incorrectly if you increase or decrease the text size. In Firefox 3: When Text and Images are zoomed together by default, some column widths or other containers may be dependent upon image size, so enlarging both may cause page to enlarge horizontally forcing use of horizontal scrolling to see text that would normally wrap within a smaller area.

Firefox 3.x

Firefox 3 also has a preference to (de)select site specific zoom and set specific zoom values. You can add more zoom values yourself. Site specific zoom options apply to the current session only.

If Firefox 3.5/3.6 is in "Private Browsing" mode then text and page zoom isn't saved to the file content-prefs.sqlite. Using "Clear Recent History" to clear the "Site Preferences" will also remove saved zoom settings.

Consider choice on View (Alt+V) > Zoom > text only, as increasing size of images may force table cells or columns to become larger and force horizontal scrolling. (in other words similar to Firefox 2)

Firefox 4.0 and above

Starting in Firefox 4, zoom toolbar buttons [-] and [+] (but not a zoom reset) can be added through Toolbar customization.

Use the "Alt" key to view the menu bar (temporarily) containing File, Edit, View, History, Bookmarks, Tools, and Help. On Windows 7 and Vista, the menu bar was hidden by default in Firefox 4 and above. These menu items are more or less available under the "Firefox" button which has the most used of the built-in Firefox menu items available in a different format. View ->Zoom is not available under the "Firefox" button. Fonts & Colors is available under the "Firefox" button -> Options (2nd column) -> Options -> Content -> Fonts & Colors.

SeaMonkey 2.x

Full-page zooming is available in SeaMonkey 2.0 and later, site-specific zoom in 2.1 and later. These settings are in Edit -> Preferences -> Appearance -> Content. Site-specific zoom values can be examined and removed in Tools -> Data Manager -> Preferences.

View -> Zoom allows to directly select a specific zoom value from the menu, which is constant up to SeaMonkey 2.4; starting with 2.5, the toolkit.zoomManager.zoomValues preference determines the stepping for both menu and Ctrl +/- keys. The list of default zoom values has been extended from 2.4 to 2.5, but the old stepping will be retained with an existing profile unless the preference is reset in about:config.

Privacy mode settings

Privacy mode settings may interfere with extensions and settings.[1][2]

Related preferences

• browser.zoom.full   true, full page zooming as opposed to text-only zooming
• browser.zoom.siteSpecific   true   (how to test)   Firefox "remembers" how much you zoomed in or out on a given website.
• toolkit.zoomManager.zoomValues   .3,.5,.67,.8,.9,1,1.1,1.2,1.33,1.5,1.7,2,2.4,3
• zoom.maxPercent   300
• zoom.minPercent   30

May help on large HD monitor

• gfx.color_management.mode = 0 (disable color management) [3]
• gfx.use_text_smoothing_setting =True (only affects OS X)

See also

• Resize images
• Resizing oversize window
• Scrolling to resize fonts and/or images
• Websites look wrong

Extensions

• Page Zoom Buttons , colorful toolbar buttons are provided to zoom in, zoom out, and reset a web page back to its default view instantly from a single toolbar button (if desired) by clicking on, scrolling over the button, or both.
• ColorZilla , statusbar button has a right-click Page Zoomer feature (incidental to color picking feature).
• Custom Toolbar Buttons Maker, buttons to "Reduce","Enlarge", and to toggle other readability features: "Full Screen", "Minimum Font Size", "Page Colours", "Page Fonts", "Themes", & "Toggle Styles"
• Default FullZoom Level Set Default FullZoom Level, Toolbar buttons for Page zoom and Text zoom. Useful on a high-definition display or for the visually impaired.
• Image Zoom, using mouse affects only a single image at a time, adds zoom and rotation functionality for images. (similar to and is compatible with MouseZoom)
• MouseZoom, using mouse affects entire page, Hold the right mouse button and turn the mouse wheel to zoom in/out. Hold the right mouse button and click left to reset to normal font size. Displays percent zoom level on screen, can also display on status bar. Both mouse buttons to reset zoom. (is compatible with Image Zoom)
• NoSquint, adjust the text-only and full-page (both text and images) zoom levels as well as color settings both globally (for all sites) and per site. Toolbar buttons, percent displays on status bar.
• Readability is a simple tool that makes reading on the Web more enjoyable by presenting the essential text of the article rendered in a larger font, removing most of the clutter of side panels, images, videos. Invoked from status bar, and back to normal with a control on left side of window. Also available as a bookmarklet which toggles on/off.
• Toggle Word Wrap, wraps PRE lines which may be exacerbated by zoom levels, also available as a style (Wrap PRE text -- http and https only).
• Zoom Page, Zooms 'Full page' or 'Text only' using two buttons in status bar next to zoom percent display, reset with click on zoom percent displayed.

Find more zoom extensions

• Search Add-ons for additional "zoom" extensions.

External links

• Page Zoom (Firefox Support)