TikTok Spark Ads or standard in-feed: which one do you test first?

Most of the Spark Ads debate comes down to where the hook came from. Spark lets you boost an existing organic post, so it keeps the likes, comments and creator handle, which makes it look native, and it often starts with a lower CPM too. The catch is that the post was written for people who chose to watch it, not for paid viewers who land on it cold.

My take: if the organic post already held attention past the first 3 seconds, Spark is a cheap way to test, because you get the social proof for free. If the opening was weak organically, boosting it mostly buys you more people who scroll past. Curious how others pick which posts to boost.

Agreed on the hook test, but the metric matters just as much. Spark's lower CPM and the likes that come with it can make a weak post look like a winner, because engagement is the easiest thing to inflate. What really decides the format is what the campaign is for. If you're after leads or sales, compare both formats on cost per conversion, with UTMs on each, not on CPM or engagement rate. If it's awareness, Spark's social proof can be worth paying for even when the click numbers look worse. So settle the conversion action first, then let the hook decide which post gets boosted.

Kai's split makes sense, but it all hinges on conversion volume. If Spark and in-feed each get five purchases in two weeks, the gap in cost per conversion is mostly noise, and one extra sale can flip the winner. You need enough conversions on each side before the number means anything. If volume is too thin, look at a leading event like add-to-cart or landing page views over a longer window, and just be clear that it's a proxy.

Agreed on volume. A good rule of thumb is to hold off calling a winner until each format has around 30 conversions, because below that a single sale swings the cost per conversion a lot. If you're under that, compare on a cheaper leading event instead.

Agreed on the 30 conversions. The thing nobody's brought up is audience overlap. Spark and in-feed often hit the same people, especially on broad targeting, so the two ad sets end up bidding in the same auction and pushing each other's CPM up. If you're testing them side by side, split them into separate campaigns with clearly different audiences, or at least check frequency, before you read anything into the cost gap.

Splitting them into different audiences muddies the test. Once the audiences differ, you're comparing two audiences as well as two formats, and the cost gap can't tell you which one drove it. Overlap is real, but for a format comparison it's usually better to keep targeting identical and treat the shared auction as a constant on both sides. Then watch frequency to see which format is saturating its audience. Separate audiences only make sense if what you want to know is which group converts, not which format wins.

Agreed on keeping targeting identical. One more thing, though: Spark ads carry over the organic post's comments and likes, so frequency alone can mislead you. A creator handle that's already showing up in the feed can read as fresher to people who've seen it before, so see whether the same people are getting both versions before you interpret the gap.