User Agent: Mozilla/5.0 (X11; Linux x86_64; rv:19.0) Gecko/20100101 Firefox/19.0 Build ID: 20130311191316 Steps to reproduce: Visited pages, such as news sites, that had clearly defined body text, but considerable clutter, with the release (19), Beta (20), and Aurora (21) versions of Firefox Mobile. For example, http://www.cnn.com/2013/03/18/world/americas/canada-prison-escape/index.html?hpt=hp_inthenews Actual results: For 20 and 21, the Reader Mode icon does not appear in the location bar when page finishes loading. Encapsulating the URL, as with "about:reader?url=www.example.com&readingList=1", led to a white page with a message, "Loading...", but that remains static, and doesn't error out. Expected results: When the page completed loading, the Reader Mode icon should have appeared in the location bar, and tapping it should have reloaded the page in reader mode. This worked correctly with the release (19) of Firefox Mobile.

Works for me as-is / no special encapsulation ... GS3 4.1.1 ... w/19.0, 20.0, nightly 22.01a-3/17.

What device are you using? Reader mode is disabled on low-memory platforms, the threshold for which is around ~384 megabytes of RAM (as reported by /proc/meminfo).

I'm using a T-Mobile G2; i.e., http://wiki.cyanogenmod.org/w/Vision_Info $ cat /proc/meminfo MemTotal: 376792 kB MemFree: 8976 kB Buffers: 22676 kB Cached: 141320 kB SwapCached: 0 kB Active: 143416 kB Inactive: 191624 kB Active(anon): 79400 kB Inactive(anon): 92272 kB Active(file): 64016 kB Inactive(file): 99352 kB Unevictable: 268 kB Mlocked: 0 kB SwapTotal: 0 kB SwapFree: 0 kB Dirty: 16 kB Writeback: 0 kB AnonPages: 171324 kB Mapped: 44000 kB Shmem: 360 kB Slab: 10608 kB SReclaimable: 3364 kB SUnreclaim: 7244 kB KernelStack: 4640 kB PageTables: 10764 kB NFS_Unstable: 0 kB Bounce: 0 kB WritebackTmp: 0 kB CommitLimit: 188396 kB Committed_AS: 1860720 kB VmallocTotal: 262144 kB VmallocUsed: 107612 kB VmallocChunk: 112644 kB

Yeah, reader mode is going to be disabled on your device, since MemTotal is less than 393216 kB. If you feel like your device is up to it, we could put in a pref to force-enable it. Based on the "MemFree" value in your output though I don't think you'll have a good experience with reader mode. :/

Well, in my case anyway, I did have the use of Reader Mode for a month or two at least on this same device, and performance was fine. I'm not sure why so much RAM is in use, though.

(In reply to Kartikaya Gupta (email:kats@mozilla.com) from comment #4) > Yeah, reader mode is going to be disabled on your device, since MemTotal is > less than 393216 kB. If you feel like your device is up to it, we could put > in a pref to force-enable it. Based on the "MemFree" value in your output > though I don't think you'll have a good experience with reader mode. :/ I'm more inclined to just offer the feature and work through performance then to deny it. Do we have any active bugs being worked on that are fine-tuning reader-mode?

I don't believe anybody is working on reader mode performance at the moment. I think that depending on how people use Firefox on low-mem devices (e.g. number of tabs open at any given time) this might impact some people more than others, so I'm a bit hesitant to turn it on unconditionally.

So this is the same as bug 828124 which was checked into 19 beta at the time but I guess did not take affect since bug 792603 was 20 only.

Not sure what resolution to close this as tbh

Reader Mode is still disabled in the latest Firefox 21 beta with my device (Xperia Ray), whereas it worked fine in earlier versions of Firefox (16-19). Denying this feature for phones with small high-res screens (for example) is a big step backwards in functionality, in my opinion. For the record, I never noticed any performance-related issues with Reader Mode in previous versions.

Likewise. I've been puzzled in that part of the utility of Reader Mode was that in eliminating most of the graphics, scripts, etc., on a page, the browser seemed to become more responsive. I would have assumed that Reader Mode required less memory for displaying a Web page than the default display.

MemTotal reported by my phone is: 343396 KB. While this may seem low, Reader Mode appeared to run just fine beforehand. A hidden pref would probably be a decent compromise for people willing to use this feature regardless of limited memory resources. Though a normal (visible) preference would be better still.

I can confirm that Reader Mode works again in the latest nightly. Thanks!

I'm using the latest nightly, and Reader Mode is still not available. Checking about:config, there is no reader.force_allow setting. Adding this setting, setting it to TRUE, and reloading pages or restarting Firefox doesn't have any apparent effect.

My mistake. The name of the setting changed to: reader.parse-on-load.force-enabled When I toggled that to TRUE, Reader Mode is available and works as expected.