Steve Jobs has set out his many criticisms of the Flash development platform in a blog post published on Apple's website on Thursday.
The Apple boss attacked Flash on six counts: openness; the "full web"; reliability, security and performance; battery life; touch compatibility; and Flash's nature as a cross-platform tool. The lengthy post is the latest round in a long-running spat between Adobe and Apple, largely relating to Apple's refusal to allow Flash onto its iPhone, iPod and iPad devices.
Apple also recently angered some developers by making it impossible for them to write apps for the iPhone or iPad using Adobe's tools.
In the post, Jobs contradicted Adobe's arguments as to why Apple had banned Flash from those devices.
"Adobe has characterised our decision as being primarily business driven — they say we want to protect our App Store — but in reality, it is based on technology issues. Adobe claims that we are a closed system, and that Flash is open, but in fact the opposite is true," he said.
Jobs said Adobe's Flash products are "100 percent proprietary", because they are "controlled entirely by Adobe and available only from Adobe". He then acknowledged that Apple's iPhone OS is itself proprietary, but highlighted Apple's belief that "all standards pertaining to the web should be open".
The Apple boss then tackled Adobe's claim that users of Apple's mobile devices miss out on 75 percent of web video because that video is in Flash. "What they don't say is that almost all this video is also available in a more modern format — H.264 — and viewable on iPhones, iPods and iPads," he wrote, while suggesting that wide-spread encoding in H.264 meant Apple's customers "aren't missing much video".
"We also know first-hand that Flash is the number one reason Macs crash," Jobs continued. "We have been working with Adobe to fix these problems, but they have persisted for several years now. We don't want to reduce the reliability and security of our iPhones, iPods and iPads by adding Flash."
He went on to say that Flash has "not performed well on mobile devices". This is an issue that Adobe has said it will address with this year's Flash 10.1. Google has already signed up to support the new version of Flash in its Android platform, which rivals the iPhone. Jobs, however, used his blog post to suggest that the new version might not perform well.
"Adobe publicly said that Flash would ship on a smartphone in early 2009, then the second half of 2009, then the first half of 2010, and now they say the second half of 2010," Jobs said. "We think it will eventually ship, but we're glad we didn't hold our breath. Who knows how it will perform?"
Jobs then criticised Flash for requiring software-based decoding in almost all web video implementations. According to the Apple chief, this doubles the power consumed in playback. He also said Flash was "designed for PCs using mice, not for touchscreens using fingers".
He also complained that Adobe's development tool is designed to address multiple platforms. "We know from painful experience that letting a third-party layer of software come between the platform and the developer ultimately results in substandard apps and hinders the enhancement and progress of the platform," he said.
"If developers grow dependent on third-party development libraries and tools, they can only take advantage of platform enhancements if and when the third party chooses to adopt the new features... This becomes even worse if the third party is supplying a cross-platform development tool. The third party may not adopt enhancements from one platform unless they are available on all of their supported platforms," he added.
Jobs concluded by claiming that "Flash is no longer necessary to watch video or consume any kind of web content".
"New open standards created in the mobile era, such as HTML 5, will win on mobile devices (and PCs too)," he said. "Perhaps Adobe should focus more on creating great HTML 5 tools for the future, and less on criticising Apple for leaving the past behind."
Adobe had not responded to a request for comment at the time of writing. In the past, the company has said that it has tried to respond to complaints about the flexibility of Flash on mobiles through its Open Screen Project, which lists 19 of the top 20 mobile device manufacturers as members.