Chrome's usage share last month was a record 51.7% according to StatCounter.
Nightingale's contention that Firefox downloads were up last month doesn't necessarily contradict the data from Net Applications and StatCounter: Because those companies' numbers represent fractions of the whole, Firefox's downloads could be climbing even as its share slumped or stalled if rival browsers were being downloaded and used in even larger numbers.
But the most recent data from the metrics firms does hint at a slightly stronger Firefox on the desktop.
According to Net Applications, last month's Firefox user share was flat compared to December 2014, for instance, the first time since August that the browser had not declined by a notable amount, perhaps indicating a turn-around was in the works.
Meanwhile, StatCounter's January usage share for Firefox was up seven-tenths of a percentage point from the month prior, and down only two-tenths of a point from a year ago.
Yet Mozilla is at a precarious point because Web browsing is increasingly shifting to mobile devices, where the non-profit has little to show for its efforts.
By Net Applications' calculation, Firefox's mobile user share — the browser is available only on Android and Mozilla's Firefox OS mobile operating system — was under 1% in January. Apple's Safari and Google's Chrome accounted for 43.2% and 26.7%, respectively, with another 15.7% attributed to Google's stock Android browser.
Mozilla has said it will develop an iOS version of Firefox that will run on Apple's iPhone and iPad, but the project, which was touted in December, has not yet resulted in a browser suitable for even the most cautious public testing.
Also on Wednesday, Mozilla's CEO Chris Beard announced that Mark Mayo will succeed Nightingale. Mayo, who joined Mozilla in 2011, will lead a newly-formed group that combines Firefox's team with the one responsible for developing Mozilla's cloud services. Mayo had headed the latter team for the last four years.
Saying that Firefox "turned a corner" in the last year, Beard added that Mozilla has big plans for the browser. "Recently we have been exploring how we can integrate client software on desktops and mobile with cloud service approaches to evolve what Firefox can do for people," Beard said. "We now have a much stronger foundation from which to build, grow and pursue our mission."
For his part, Nightingale said he has no immediate post-Mozilla plans. "No, I haven't been poached by Facebook," Nightingale said. "I don't actually know what my next thing will be. I want to take some time to catch up on what's happened in the world around me. I want to take some time with my kid before she finishes her too-fast sprint to adulthood. And I want a nap."
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