On Fx Android you can use https://addons.mozilla.org/en-US/android/addon/always-reader...

Alternatively, a keyboard shortcut would be great.

If you're willing to install an addon, there is: https://addons.mozilla.org/en-US/firefox/addon/autoreadervie... (I'm in no way affiliated with the author of the addon, nor do I use it — with Vimperator, I'm just a "gr" away from reader mode anyway.)

Thanks for the suggestion! I'll give it a try.

Unfortunately most sites I visit don't offer reader view as an option.

Is it something the site has to offer? I thought it was just something the browser was doing on its own, for any page meeting some (undocumented?) criteria.

You're correct, the browser extracts and reformats the content. Firefox only shows the Reader View icon for pages where it thinks it can do a good job of that.

I find myself wondering if it relies on the "for printing" reformating of various sites. This because i was browsing one site i could have sworn had the icon earlier using desktop Firefox, but it didn't show up. That is until i enable the JS of s third party printing framework in Noscript. After that it showed up.

It's using this code:

https://github.com/mozilla/readability/blob/master/Readabili...

which is a descendant of the original Readability.js published by Arc90, before they decided to turn it into a proprietary Instapaper clone.

It extracts what looks like article text from the page markup. DOM elements included for a printer-friendly view could possibly be helping, but it doesn't target that directly.

I'm not entirely sure what is going on with reader view on Firefox mobile, but sometimes it doesn't show the icon in the URL bar. However, if you open the hamburger menu and add the page to your reading list (the "book+" icon), then switch to the reading list and open the page from there, you can sometimes get reader view when it's not otherwise available.

Scrolling slightly down the page then refreshing also does the trick without needing to clear it from your reading list. Just a refresh sometimes works but it's inconsistent.

I suspect it's looking at the page before it's fully rendered and determining that it doesn't meet some criterion for reader mode.