Mozilla Release Firefox 5

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If you’ve been waiting to upgrade to Firefox 4, you’re too late! As promised, Mozilla released Firefox 5 on June 21 2011 — just three months after version 4 was launched. The organization has embarked on a Chrome-like release-little, release-often rapid-update schedule.

If you’re too excited to read further, download the installer from or update by selecting Help > About Firefox > Check for Updates. You may be lucky enough to receive a fast incremental update — it didn’t work for me and the full installer was downloaded.

Firefox 4 was a major update. You’re unlikely to spot any immediate differences in version 5 since most of the changes are under the hood:

  • support for CSS3 animations with the -moz prefix
  • improved JavaScript and canvas performance
  • additional HTML5, SVG and MathML features
  • faster browsing

Developers should also note that setTimeout and setInterval events will only execute once per second or less frequently on inactive tabs. It replicates the behavior of requestAnimationFrame to save CPU and power consumption.

Great — but there’s a downside. You may find several of your add-ons are disabled by Firefox 5. They should work, but many authors have not yet updated their add-on’s version numbers. Firebug and the Web Developer Toolbar are fine, but Console2 and HttpFox are blocked.

Not every plugin author has the time or resources to match the new schedule. It’s unfortunate and I hope Mozilla can address the problem. Perhaps a less formal approach could be adopted which allows the community to test and approve plugins without relying on the author to hard-code supported versions. Alternatively, Mozilla could have simply released Firefox 4.1 — the numbering is becoming increasingly irrelevant.

Despite the add-on hassles, it’s good to see updates appearing more regularly. Let us know what you think of the Firefox 5.

Craig BucklerCraig Buckler
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Craig is a freelance UK web consultant who built his first page for IE2.0 in 1995. Since that time he's been advocating standards, accessibility, and best-practice HTML5 techniques. He's created enterprise specifications, websites and online applications for companies and organisations including the UK Parliament, the European Parliament, the Department of Energy & Climate Change, Microsoft, and more. He's written more than 1,000 articles for SitePoint and you can find him @craigbuckler.

firefoxFirefox 5Mozilla
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