This is a common question, and a fair one to ask before downloading anything — here's a straightforward, non-legal-advice look at how it generally breaks down.
Personal use
Saving a clip to watch later, archive privately, or reference offline is generally considered low-risk. You're not distributing anything or presenting it as your own — it's closer to bookmarking a video than publishing something, and that distinction matters for how platforms and rights holders typically treat it.
Where it gets riskier
Reposting someone else's clip on your own channel, using it in a monetized video, or presenting it as your own content is a meaningfully different situation. The footage still belongs to the streamer, and it often includes game footage owned by a separate publisher on top of that — two layers of rights, not one. Reusing either without permission can raise real copyright concerns that exist independently of whatever the platform's own terms of service say.
A brief note on fair use
Fair use is a real legal concept that can sometimes cover things like commentary, criticism, or parody, but it's decided case-by-case and isn't a blanket permission slip — simply crediting the original creator or keeping a clip short doesn't automatically make something fair use. If you're building something monetized around someone else's footage, that's exactly the situation where getting explicit permission first is worth the extra step.
Platform terms of service
Twitch's and Kick's own terms govern how content on their platforms can be used, and both generally expect you to have the streamer's permission before redistributing their clips elsewhere. A downloading tool doesn't change what those terms say — it just gives you the file, functionally similar to what a screen recording would produce.
Monetization-specific risk
If you're uploading edited clips to a platform like YouTube, automated content-matching systems can flag video or audio that isn't yours, even in a compilation with several sources mixed together. That's a separate, largely automated enforcement layer on top of the underlying copyright question, and it's worth knowing about if monetization is part of your plan.
The practical takeaway
If it's your own content, or you have explicit permission from the person who made it, you're on solid ground. If you're unsure, ask the streamer directly — most are reasonable about it if you credit them and ask first, especially for non-monetized use like fan edits or highlight reels shared for free.
This is general information, not legal advice. If you need a definitive answer for a specific situation, talk to a lawyer.