How to Add Captions to AI UGC Reaction Clips in CapCut

A reaction clip and a caption do different jobs. The expression earns a second of attention; the words tell the viewer why the reaction matters to them. If your AI UGC reaction is silent, CapCut's Auto captions cannot invent the hook for you. Add it as a manual text layer, then cut to footage of the product doing what the caption promises.

This walkthrough uses a short reaction clip, a fictional planning-app example, and a real screen recording supplied by the app. It works as an editing pattern whether the source clip comes from the RE/UGC library or another properly licensed source. For the strategy behind that first beat, see UGC reaction hooks.

Before you open CapCut

• Choose one vertical reaction with an expression that fits the claim. A mild discovery line rarely needs a theatrical shock face.
• Record the actual app workflow: the input, the action, and the resulting screen. Hide personal or test-account data you cannot publish.
• Write one short hook that the demo can answer. Example: ‘Wait, my notes can become a plan?’
• Check the clip license, music rights, and any AI-content labeling required by the platform where you will post.

Step 1: Place the reaction before the demo

Create a vertical project in CapCut and import both files. Put the AI UGC reaction first and the app screen recording immediately after it. Trim the reaction to the moment that communicates the expression—often a few seconds—and use a direct cut rather than a long transition. Keep the product action early enough that the opening question has a visible answer.

Step 2: Add a manual hook caption

On CapCut Desktop, add a text layer over the reaction in the Text area; on mobile, use Text → Add text. The exact menu placement may vary by version. Enter the hook, time the layer to the reaction, and keep it readable without obscuring the face. This is on-screen copy, not a transcript. A silent source clip needs this manual step even if you plan to use automatic captions later.

Step 3: Caption spoken audio, if you have it

If your demo has narration or speech, use CapCut's Auto captions tool, choose the spoken language, then review every word and its timing. CapCut documents this workflow for Desktop and mobile. Correct product names, prices, and claims manually. If the edit has no speech, skip auto captions; the manual hook and any short explanatory demo labels are enough.

Step 4: Match the caption to the payoff

The timings are a starting point, not a performance guarantee. Avoid captions that claim a saved amount of time, a personal experience, or a customer result unless you can support them. With AI UGC, the character is a creative opener; the product screen carries the factual demonstration.

Step 5: Export and inspect on a phone

1. Play the edit muted. The opening and product action should still make sense.
2. Check that the caption is clear of platform controls and readable on a small screen.
3. Read every generated subtitle against the audio and check spelling of the product name.
4. Export the vertical video, watch the exported file rather than only the editor preview, and confirm the cut and text timing survived.

CapCut's own caption guide covers the current auto-caption controls and export flow. For a closer look at different reaction-and-demo pairings, see the AI UGC examples for apps and SaaS.