Changes to the way Twitter allows its service to be used by applications have angered developers, who claim the updates will restrict them from working with the social network.

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The changes will take effect in six months' time and will require any new application using Twitter to seek explicit permission from the company before it can expand to more than 100,000 users.

Twitter clients that already have more than 100,000 users will be allowed to grow by 200 percent from their current size before having to get Twitter's permission to increase further - those against the changes claim this will lead to less development of new and innovative products that work with Twitter.

The changes affect how Twitter handles its Application Programming Interface (API), which allows 3rd party apps to share content with Twitter. Such apps include Tweetdeck, Tweetbot and Twitpic.

Developers are worried that restricting how many users they can have will have a knock-on effect in giving them less opportunities to place adverts, leading to decreased revenue.

Instapaper creator Marco Arment said in a blog post: "Twitter has left themselves a lot of wiggle room with the rules.

"Effectively, Twitter can decide your app is breaking a (potentially vague) rule at any time, or they can add a new rule that your app inadvertently breaks, and revoke your API access at any time."

Twitter's director of consumer product Michael Sippey wrote on the company's developer blog: "In the coming weeks we will release version 1.1 of the Twitter API. To help you plan ahead, we're announcing these changes now, before the new version of the API is available."

In a bid to limit "abusive applications" that call for information too often from Twitter's servers, the site will lower the limit of calls most application can make from 350 per hour, to 60 per hour per user.

Sippey added: "Based on analysis of current use of our API, this rate limit will be well above the needs of most applications built against the Twitter API, while protecting our systems from abusive applications.

"There will be a set of high-volume endpoints related to tweet display, profile display, user lookup and user search where applications will be able to make up to 720 calls per hour per endpoint."

The changes also cover how tweets are displayed within apps, Sippey explained: "If your application displays Tweets to users, and it doesn't adhere to our Display Requirements, we reserve the right to revoke your application key."

Arment concluded: "Twitter has proven to be unstable and unpredictable, and any assurances they give about whether something will be permitted in the future have zero credibility.

"I sure as hell wouldn't build a business on Twitter, and I don't think I'll even built any nontrivial features on it anymore."

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