Cross-posting is not the mistake
Using the same underlying content across several platforms is a reasonable, common choice. Most accounts do not have the time to create entirely separate content per platform, and they should not feel obliged to. The mistake is doing it with zero adjustment for where the content lands.
What needs to change per platform
A few adjustments carry most of the benefit, without needing a full rewrite per platform:
- Aspect ratio and crop: a vertical video posted uncropped on a platform expecting horizontal reads as an afterthought
- Caption length and tone, since a caption written for one platform’s audience often reads oddly copy-pasted onto another
- Whether a link is even clickable. Some platforms allow a link in the caption, others only in a bio, and a caption that assumes the wrong one wastes the click
When fully platform-native is worth the extra effort
For a platform that is a real priority, the one place a large share of your audience lives, content built specifically for that platform's format and norms from the start usually outperforms an adjusted cross-post. Reserve that effort for the platform that matters most, and let cross-posting cover the rest.