# How to turn a WebM recording into vertical video clips > Make vertical MP4 clips from a WebM screen recording or interview. Check finalized files, audio tracks, screen detail and the finished export. By CastCuts · Updated 2026-10-25 Upload a completed WebM recording that contains both picture and sound, then choose a short passage and a vertical layout. CastCuts accepts validated WebM sources and renders clips as MP4. Start by checking the downloaded recording itself: an audio-only WebM or an unfinished recording cannot become a usable video clip through framing alone. ## Finish and verify the recording before uploading Stop the recording in the original application and let its save or download operation finish. Open the complete file locally and seek near the end. Check whether the recorded audio includes the guest, the microphone and any application sound the explanation requires. If your recorder provides several downloads, choose the actual video file rather than a transcript, audio-only export or a project link that needs the recording application. ## Try the supported WebM before adding a conversion WebM is a media container commonly associated with VP8/VP9 video and Opus/Vorbis audio. The contents still matter more than the suffix. Upload a valid source directly when possible. If a player or validation fails, create an H.264/AAC MP4 working copy in an external editor and test it first. Keep the original WebM; changing its filename to .mp4 does not convert the streams. ## Choose a moment that survives a smaller screen Screen recordings often show a wide desktop with small labels. Full-frame layout preserves that desktop inside the portrait canvas but makes its details smaller. A fixed crop can focus on a stable area while removing menus or another participant. Play the entire passage to check cursor movement and pop-up windows. If understanding requires tiny changing text, prepare a clearer demonstration externally or select an explanation that works without it. ## Review the MP4 as a separate deliverable Select a complete 1–90 second passage, correct available English captions and render the clip. CastCuts produces 720 × 1280 portrait MP4 video, rather than a vertical WebM download. Inspect the saved file on a phone: verify speech, cursor visibility and any essential labels. Publish it manually in the destination’s normal upload flow. Save finished files before the source episode’s 24-hour retention period ends. ## A fictional browser-recorded product explanation Illustrative example. The people, recordings and results described here are fictional. A creator has a WebM interview with a 20-second screen demonstration. Full-frame playback shows the whole browser, but the setting being discussed is unreadable on a phone. The cursor stays in one panel, so the creator tests a fixed crop of that area. When the speaker opens a dialog outside the crop, they choose an earlier verbal explanation for the short clip instead. A successful format import does not guarantee that the screen content makes a useful portrait excerpt. ## Check before you finish - The recording is finalized and can seek through its final passage. - The file includes both usable video and the required audio. - The chosen layout preserves the demonstration throughout the excerpt. - The downloaded MP4 has been checked on a small screen and saved. ## Practical questions ### Do I need to convert WebM before uploading? Not necessarily. CastCuts accepts validated WebM video with audio. Convert externally when a specific file has a compatibility problem, and check the converted copy before uploading it. ### Why does my WebM contain sound but no picture? A WebM can contain audio without video. Check the original recorder’s export options; CastCuts requires both tracks and cannot invent the missing picture. ### Can I export a vertical WebM from CastCuts? The current clip output is a 9:16, 720 × 1280 MP4 with H.264 video and AAC audio. WebM is an accepted source, not the export format. ## Use this workflow in CastCuts [Prepare a recorded demonstration for short clips](https://castcuts.co/webinar-to-shorts) CastCuts selects continuous 1–90 second excerpts and exports 9:16, 720 × 1280 H.264/AAC MP4 files. Automatic transcription and transcript-based suggestions support English and require review. Free exports include CastCuts branding; Pro removes it from new renders for $9 USD/month, with the same processing and storage limits. Episode media is retained for 24 hours. Keep your originals and download finished clips before expiry. Publishing is manual. ## Sources [The WebM Project: about the format](https://www.webmproject.org/about/) ## Explore this topic [Podcast recording to clips: prepare, import and preserve your files](https://castcuts.co/guides/topics/recording-workflows) ## Keep creating [How to prepare a video file for podcast clipping](https://castcuts.co/guides/prepare-video-for-podcast-clipping) [How to make podcast clips with slides and screen shares](https://castcuts.co/guides/podcast-clips-with-slides) [Why podcast clips look blurry and what to check first](https://castcuts.co/guides/blurry-podcast-clips) [All creator guides](https://castcuts.co/guides) [Create a clip](https://castcuts.co/account)