https://support.mozilla.org/en-US/kb/how-to-fix-preferences-wont-save

Note: Some software, like Advanced SystemCare with Surfing Protection, can protect files in the Firefox profile folder against changes. If you have such software then check the settings or uninstall this software.

This came up the other day, and it's probably a bug. Other thread: https://support.mozilla.org/questions/1187487

When I looked at the source code, the problem appears to be a "migration" feature which computes the number of "Activity Stream" top sites tiles by multiplying the browser.newtabpage.rows preference by 6. So if you started with

browser.newtabpage.rows = 4

then in about:config you should see:

browser.newtabpage.activity-stream.topSitesCount = 24

instead of the default value of 12. But!! The migratePref() function then resets the browser.newtabpage.rows value back to default. There's yer trouble.

I don't understand the code well enough to figure out whether there is a way to stop the migratePref() function from running.

Possible Workarounds

(A) Since the tiles "wrap" to fit the available space in the old design, can you work around this behavior by increasing browser.newtabpage.columns to multiply out to approximately the same number of tiles you wanted?

(B) Switch to using the New Tab Tools extension.

FredMcD said

https://support.mozilla.org/en-US/kb/how-to-fix-preferences-wont-save Note: Some software, like Advanced SystemCare with Surfing Protection, can protect files in the Firefox profile folder against changes. If you have such software then check the settings or uninstall this software.

only software that would qualify as "system-helpers" on my pc are kaspersky and malwarebytes, and i dont think they are the culprits. besides, why only browser.newtabpage.rows resets then, and not browser.newtabpage.columns? which stays at the value i set. more importantly i think that jscher2000 wrote is correct. although i am not that tech-savy and my competence starts and ends and changing row/column values. i can only hope that mozilla acknowledges this as an official bug and fixes it in near feature.

BoromiRofGeo said

i am not that tech-savy and my competence starts and ends and changing row/column values.

Hopefully one of the two workarounds I suggested will handle it until there is an official fix.

That is how it appears to work with Activity Stream enabled.

Activity Stream uses its own way to display tiles and uses a maximum and automatically adjusts rows and columns. This maximum is calculated from the row and column settings when these prefs are found and once calculated they chose to reset the row pref to 3 instead of keeping its modified value. The only way to prevent this is to use a mozilla.cfg file to lock this specific pref.

Other threads about this issue:

• [/questions/1194236] Changing number of rows in newtabpage doesn't work
• [/questions/1187487] New tab page rows problem

cor-el said

That is how it appears to work with Activity Stream enabled. Activity Stream uses its own way to display tiles and uses a maximum and automatically adjusts rows and columns. This maximum is calculated from the row and column settings when these prefs are found and once calculated they chose to reset the row pref to 3 instead of keeping its modified value. The only way to prevent this is to use a mozilla.cfg file to lock this specific pref. Other threads about this issue:

• [/questions/1194236] Changing number of rows in newtabpage doesn't work
• [/questions/1187487] New tab page rows problem

how do you think, is there any chance mozilla will fix this, or this is just a by-product of new design and here to stay for a foreseeable future?

There is this bug mentioned in the threads, but no activity from devs:

• bug 1406088 - browser.newtabpage.rows (manually config reset at each restart)

(please do not comment in bug reports
https://bugzilla.mozilla.org/page.cgi?id=etiquette.html)