Every ad needs cutaways — the shots between the talking and the text that keep a video alive. For years that meant stock libraries. Now you can generate B-roll on demand. Both fill the same slot in your edit, but they get there differently, and the tradeoffs are worth knowing before you build your next ad.
How they compare
| AI-generated B-roll | Stock footage | |
|---|---|---|
| Relevance | Made for your exact shot | Closest available match |
| Uniqueness | One of a kind | Shared across many brands |
| Licensing | Generated for you | Depends on the library terms |
| Cost | Per render | Per clip or subscription |
| Control | Describe and re-render | Pick from what exists |
| Predictability | Varies by prompt | What you see is what you get |
Where stock still shines
Stock footage is proven and instant. The clip already exists, shot by a professional, and you can preview exactly what you're getting before it lands in your timeline. For real-world specifics — a recognizable city, a particular kind of machinery, genuine human crowds — a good library often beats anything generated, because it's actual footage of an actual thing.
Stock is also reliably high-quality. There's no prompt to wrestle, no roll of the dice on whether the shot comes out right. If you need a safe, polished cutaway in thirty seconds, it's hard to argue with.
Where AI B-roll pulls ahead
The case for AI B-roll is relevance and uniqueness. Instead of searching for the nearest match and settling, you describe the exact shot your ad needs — your product's color, your specific setting, the precise mood — and render it. The result is built for your story, not adapted from someone else's.
It's also yours alone. Stock clips show up in dozens of competing ads; viewers (and platforms) notice the same overused footage. AI B-roll gives you visuals no one else has, which matters when you're trying to stand out in a crowded feed.
And it composes naturally with the rest of your ad. In Krex AI, AI B-roll lives in the same pipeline as talking-head avatars and text-to-video, so you can cut from a person to a custom scene to a product shot in one render — each one 1 credit = 1 video. You're not stitching a stock subscription into a separate editor.
The honest tradeoff: generated footage takes iteration. You may re-prompt to land the shot, and hyper-specific real-world subjects can be harder to nail than picking an existing clip.
A practical mix
You don't have to commit to one source. A reliable approach:
- Use stock for real-world specifics and safe, instant cutaways.
- Use AI B-roll when you need a shot that's exactly yours, unique to your brand, or impossible to find.
The best edits blend both — proven footage where it fits, custom shots where it counts.
Which should you pick?
Choose stock when speed and a guaranteed real-world shot matter most. Choose AI B-roll when relevance, uniqueness, and a one-of-a-kind look are worth a little iteration — and when you'd rather keep everything in one pipeline instead of juggling licenses.
Want to test custom B-roll against your usual stock? Render a few on the Free tier and compare them side by side. Start at the overview if you're new.