Sandcastles and Reelyze both work from a video URL, so they get compared, but they do opposite jobs. Sandcastles is about ideation: find what is already winning in your niche and remix it. Reelyze is about diagnosis: understand why your own video performed the way it did. This guide covers what each is best at and when you would reach for one over the other.
What Sandcastles is good at
- Discovering top creators and viral outliers across Instagram, TikTok, and YouTube Shorts.
- Pulling a video's transcript, caption, hook, hook format, storytelling structure, and public metrics.
- Generating dozens of hooks and viral scripts from proven templates.
- Building a content research library you can export in bulk.
Where the Sandcastles workflow stops short
Sandcastles extracts data about videos, but it does not synthesize the verdict for you. Its own recommended workflow ends by exporting the data to a CSV and pasting it into an AI chat to get the breakdown. In other words, the intelligence step, what does this mean and what should I do, still happens manually outside the tool. It also analyzes other creators' videos to find patterns, not your own video to explain why it underperformed.
Where Reelyze is different
Reelyze watches your own video frame-by-frame and does the analysis natively, no CSV and no separate AI prompt. Paste any Reel, TikTok, or Short and it scores the hook, maps the retention curve, pinpoints the exact second viewers left, and tells you the specific fix, all in one report. Reelyze also has a Content Studio that writes hooks and scripts from what works in your niche, so it covers the ideation side too, but its core is the diagnosis that research tools cannot do: explaining your own video.
Which one should you pick?
If your bottleneck is running out of ideas, Sandcastles, with its large database of validated outliers, is strong at filling the pipeline. If your bottleneck is posting videos that underperform and not knowing why, Reelyze is the focused tool, because it watches the video itself and hands you the verdict. Many creators run both: Sandcastles to plan, Reelyze to diagnose and improve. Reelyze starts free, with the first analysis included and open transcript, downloader, and audio tools that need no sign-up.