The size of text by default is under the control of the website.

The font size setting in Firefox only applies to increasing the size of text on Desktop style websites. Mobile style websites do not get the text size increased.

On sites that allow it you can Pinch zoom out to make the text smaller.

For many articles/sites Firefox is able to find the main body of text and provide a Reading Mode format. This will allow you to increase the font size. You can read how to use the Reader Mode feature here: View articles in Reader View on Firefox for Android

You might also be interested in the Always Zoom add-on which overrides the website's settings and allows you to zoom on any page.

When I compare e.g. the amazon homepage in firefox on my laptop and tablet, icons, fonts etc. have the same size in cm. but since my tablet's display hasthe same resolution but a smaller diameter, everything is bigger measured in pixels. So how does a website gain info about my screen size? I've overridden my user agent, but that didn't change anything either... I don't want websites to adjust their layout to my screen size, but to my screen resolution. Like on a windows desktop PC. Is there a way to do that?

This is an interesting one. I'm not a web developer so others will be able to give a more thorough answer but I think the thing is that the navigator.userAgent is not the only source of information about your device available to the site.

Recently user agent sniffing has become less popular because browsers tend to catch each other up and, for example, you don't want to force IE10 users to view a web page designed to get around lacking features in IE6. See the following links for more info on this:

• http://jibbering.com/faq/notes/detect-browser/
• http://stackoverflow.com/questions/8970800/is-server-side-useragent-detection-bad
• https://developer.mozilla.org/en-US/docs/Browser_detection_using_the_user_agent

I expect what is happening is that the site is instead using feature detection of some kind and is varying the images served based on the features it can detect rather than the useragent string of the browser you are using.

As far as I can tell there is no setting in Firefox for Android that is default-zooming in on desktop websites. It just displays what the site provides.

thanks for the answers so far :) would be interesting to know if there was a way to emulate a bigger screen...

websites can also detect details about your screen size & density over javascript....

http://browserspy.dk/screen.php
http://browserspy.dk/resolution.php

After disabling javascript, restarting firefox and deleting cookies, browserspy.dk can no longer access info about my screen size. amazon still seems to know the size of my screen though... :/

In about:config there's the setting something.css.pixelsperpx . Its standard value is -1 which means it is using the system's dpi value, i guess. When changing that value to a positive value, most websites will scale with this value. all but amazon... this sucks! :D

Hello, can anyone help, please. For some unknown reason my mobile-optimized site looks abnormally HUGE on Firefox, but normal on Internet Explorer. And, as such, Is there any way that I can reduce my site's size (permanently) to "normal," as I don't want it to be viewed by other Firefox users like this.

Many thanks.

EPS23.

Hello EPS23,

This is a slightly different question to the OP. You will get a better range of responses if you start a new question here:

https://support.mozilla.org/en-US/questions/new