Instagram video may be putting a dent in Vine's growth. As noted by MarketingLand, in the week since Instagram added video, Vine links on Twitter seem to have dropped precipitously. Data from the analytics firm Topsy, which has access to the full firehose of Twitter data, showed the number of shared Vine links declining from almost 2.5 million on June 19 to just over 1.5 million on June 20, when Facebook-owned Instagram added video. It comes just weeks after Topsy data showed that Vine shares had surpassed Instagram shares.

As of yesterday, Vine links on Twitter had declined to 900,000 per day — or about 70 percent fewer than their peak earlier this month. When he announced Instagram video, CEO Kevin Systrom took pains to distinguish the product from its competitors, noting the 15-second clips and easy edit features. For its part, Twitter's Vine team has been cranking out updates, most recently adding a self-facing camera to the Android app today. But Topsy's numbers suggest the mobile video apps are in head-to-head competition for users' attention — and for now, the momentum may have shifted to Instagram.

Twitter declined comment.

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