The two platforms look similar and reward opposite things. Confusing them is the most common reason a video that performed on one dies on the other, and the difference is not aesthetic. It is structural.
The one difference that matters most
TikTok is watched with sound on. The Meta feed is watched with sound off.
Everything else follows. On TikTok, what is said can carry an ad: a spoken line in the first second is a legitimate hook. On Instagram, particularly in the feed, a video that only makes sense when heard is invisible to most of the people it reaches. Build for silence there and treat audio as a bonus.
This is why "just cross-post it" produces such uneven results. The file works; the assumption behind it does not travel.
Hook structures that hold up on both
Whatever the sound situation, the first second has to pose something rather than announce something.
- The impossible-looking state. The bottle upside down in a bag. The chair folded to nothing. A visual that makes a viewer wait for the resolution.
- The direct question. Not rhetorical, not clever. The literal thing your customers ask you.
- The comparison, immediately. Two objects side by side in frame one. No setup.
- The result first. Show the after, then reveal the before. It inverts the natural order and that is exactly why it holds.
What does not work on either platform: a logo, a slow fade, a sentence that takes three seconds to arrive at its point, or anything that assumes the viewer already knows who you are.
Format per placement, always
- TikTok, Reels, Stories: 9:16, planned vertical from the start. A crop from landscape puts your product behind the caption and the buttons.
- Instagram feed: 1:1 or 4:5, which holds more of a phone screen.
- Both: legible on a small screen at arm's length. If you have to squint on a laptop, it is gone on a phone.
Generating for a second placement from the same product link takes minutes, which is almost always a better trade than cropping.
Length
Shorter than instinct suggests, and shorter than the platform's maximum. The €5 entry offer produces one short clip of about 12 seconds, which is a realistic length for both platforms. The paid plans produce multi-chapter videos of 24, 32 or 36 seconds for when a product genuinely needs a second beat, built from 12-second chapters with audio continuity between them.
The test is whether every second is doing work. A 30-second ad in which seconds 8 to 15 restate seconds 1 to 7 is a 15-second ad wearing a costume.
Testing is the actual skill
Nobody predicts which angle will win. What separates people who do well is that they run the loop: generate two or three genuinely different ads, run them against each other with modest budgets, keep the winner, generate new challengers. Each generation plans its own angle, so you are testing ideas rather than crops of one idea.
The loop only survives if producing a variant is cheap. That is the whole argument.
Related reading: AI video for TikTok and AI video for Instagram.