In short: for 4K clips, press ⚡ Make a light preview copy — playback becomes smooth and export still uses the full-quality original. Export with the fast (frame-perfect) path when the editor offers it, and choose 4K only if your audience will see it.
Why 4K is heavy
At 30 fps, 4K means decoding about 250 million pixels per second, plus applying filters, text and effects to each frame in real time. Phone footage is also highly compressed (H.264 or HEVC), so every frame must be reconstructed from the frames around it. Seeking backwards through such a file is especially expensive. Laptops without strong hardware decoding stutter; phones may drop frames.
Edit with a preview copy (proxy)
Professional editors solve this with proxies: small, easy-to-decode copies used only while editing. VDOAPP builds one for you.
- Select a 4K clip and open the Clip tab.
- Under Preview copy, press ⚡ Make a light preview copy. The editor re-encodes the clip at a small size in the background; its timestamps match the original exactly, so every cut lines up.
- Edit normally. Playback, scrubbing and effects are now smooth.
- Export. The full-quality original is used automatically. Use the original switches the preview back if you want to check fine detail.
Fast export vs real-time export
VDOAPP has two ways to export, and the export window tells you which one will run:
| ⚡ Fast export | Real-time export | |
|---|---|---|
| How | Decodes and encodes every frame directly with the browser's video engine (WebCodecs) | Plays the project once and records it |
| Speed | Usually faster than real time | Exactly the project's length |
| Frames | Frame-perfect — no drops | Can drop frames on slow devices |
| Format | Always MP4 | MP4 or WebM, depending on browser |
Fast export needs WebCodecs support and clips it can read directly. It falls back to real time if, for example, a clip is WebM, a speed-changed clip has sound, or a music file is too large to decode in memory — and the window says which reason applies. For real-time export, keep the tab visible and avoid heavy work on the computer until it finishes.
Choosing export settings
- Resolution: 4K only if you shot 4K and the destination shows it (YouTube does; most social apps compress to 1080p anyway). 1080p is the right default.
- Frame rate: match your footage — usually 30, or 25 in PAL regions. Choose 60 only for 60 fps footage such as sports or gameplay.
- Quality: High for uploads; Maximum when the platform will re-compress heavily and you want to give it the best source; Standard for sharing by message.
The 4K option is switched off on iPhone and iPad, where a 4K export needs more memory than the browser allows. See export settings explained for more detail.
iPhone HEVC and HDR
iPhones record HEVC (H.265) by default, often in HDR (Dolby Vision). Safari decodes HEVC natively; Chrome and Edge do on most recent Windows and Mac hardware. Browsers show HDR footage in standard dynamic range when drawing it for editing, and the export is standard range too, so colours may look slightly different from the Photos app — a gentle Contrast and Saturation boost in the Filter tab usually brings back the punch. If you want to avoid HDR entirely, set the iPhone camera to record "Most Compatible" or switch off HDR Video.
Memory and long projects
- Browsers limit how much memory one tab can use. Many long 4K clips can hit that limit — make preview copies and remove clips you're not using.
- Close other heavy tabs while exporting.
- Your project autosaves in your browser. If the tab ever crashes, reopen the editor and choose Continue.
Frequently asked questions
Does the preview copy reduce export quality?
No. It's only used for playback while editing; export reads the original file.
Why is the 4K button greyed out?
On iPhone and iPad, 4K export is disabled because it needs more memory than the browser gives a web page. Export at 1080p there, or use a computer for 4K.
Can I edit 4K on a phone?
Short clips, yes, especially with preview copies. For long 4K projects a computer is much more comfortable.