YouTube Shorts & TikTok Converter
Resize any video to 1080×1920 vertical MP4 for YouTube Shorts, TikTok, and Instagram Reels. Pad or crop mode. Browser-only, no upload.
published
- [FREE]
- [NO_SIGNUP]
- [NO_UPLOAD]
A YouTube Shorts and TikTok converter that reshapes any source video into the 1080×1920 vertical 9:16 MP4 format YouTube Shorts, TikTok, and Instagram Reels all expect. Drop a horizontal recording, a square clip, or a too-tall portrait video; the tool scales and pads or crops it into the correct frame, encodes it as H.264 + AAC MP4, and hands you a file you can upload directly to any of the three platforms. No upload, no account, no watermark. Powered by FFmpeg compiled to WebAssembly.
How to use the converter
- Drop your videos. Multiple files at once are fine — each gets its own row.
- Pick a fit mode. Pad surrounds the source with black bars to preserve every pixel. Crop fills the entire 9:16 frame and trims whatever does not fit.
- Pick a quality preset. Balanced (CRF 23, 128k audio) is the default and is visually transparent for most content. Strong shrink (CRF 28, 96k audio) for the smallest file. High quality (CRF 20, 160k audio) for archive use.
- Click Convert all. The first run downloads the FFmpeg core (~30 MB) once and caches it. Each video processes sequentially with per-percentage progress.
- Grab the output. Each row gets a download button. The file is ready to upload directly.
What “Shorts / TikTok / Reels format” actually means
YouTube Shorts, TikTok, and Instagram Reels all share the same recommended upload spec:
- Aspect ratio: 9:16 (vertical).
- Resolution: 1080×1920 (other sizes are accepted but may be downscaled or letterboxed inside the player).
- Container: MP4.
- Video codec: H.264.
- Audio codec: AAC.
- Frame rate: matches source (the tool passes the source rate through; no resampling).
Off-spec uploads still play, but they render with the platform’s own letterboxing inside a smaller box, or get demoted from the Shorts/Reels shelf to a regular video. Hitting the recommended spec is the cheapest way to guarantee the upload behaves.
Duration caps per platform
| Platform | Max duration |
|---|---|
| TikTok | 10 minutes |
| YouTube Shorts | 3 minutes |
| Instagram Reels | 3 minutes |
This tool does not trim; if your source is longer than the platform cap, run it through the Video Splitter & Joiner first to cut it down (or split into multiple parts).
Pad vs Crop, visually
| Source | Pad result | Crop result |
|---|---|---|
| Landscape 1920×1080 | full landscape with black bars top + bottom | center 9:16 strip; sides trimmed |
| Portrait 1080×1920 | already 9:16 — no bars, no crop | identical to Pad |
| Tall portrait 1080×2400 | scaled to fit; black bars on the sides | center 9:16 vertical window; top + bottom trimmed |
| Square 1080×1080 | scaled to fit; large black bars top + bottom | center vertical strip; sides trimmed |
Rule of thumb: if your subject hugs the edges (multiple speakers in a horizontal interview, on-screen text), pad. If your subject is centered (a single person, an object), crop.
The three quality presets
Each preset bundles a CRF value (constant rate factor — the H.264 quality knob, where lower means higher quality and bigger file) with a matching audio bitrate.
| Preset | CRF | Audio | Use when |
|---|---|---|---|
| Strong shrink | 28 | 96 kbps | Smallest file. OK for talking-head content. |
| Balanced | 23 | 128 kbps | Default. Visually transparent for most content. |
| High quality | 20 | 160 kbps | Archive-grade. Overkill for upload, fine for re-editing. |
Privacy
Same posture as every other tool on the site. A static HTML page loads its JavaScript, then fetches the FFmpeg WebAssembly core once from a public CDN (cdn.jsdelivr.net) — the core is just the encoder binary, no user data ever leaves the tab. After that one-time download, DevTools → Network shows zero outbound requests on subsequent conversions. There is no upload, no temporary cloud storage, no analytics on file contents, no watermark.
Related tools
- Video Splitter & Joiner — split or merge videos before converting.
- Video Compressor — re-encode without changing aspect ratio.
- Aspect Ratio Calculator — math for arbitrary dimensions.
Frequently asked questions
What format does YouTube Shorts, TikTok, and Reels require?
All three platforms use the same vertical 9:16 aspect ratio at 1080×1920 pixels, MP4 with H.264 video and AAC audio. The only meaningful difference is duration: TikTok allows up to 10 minutes, YouTube Shorts up to 3 minutes, Instagram Reels up to 3 minutes. This tool always outputs the 1080×1920 H.264 + AAC MP4 spec; trim with the Video Splitter & Joiner first if you need to cap duration.
Does the same file work on all three platforms?
Yes. A 1080×1920 H.264 + AAC MP4 uploads cleanly to YouTube Shorts, TikTok, and Instagram Reels without re-encoding on the platform side beyond their own quality pass. One file, three uploads.
Pad vs Crop — which should I pick?
Pad keeps every pixel from the source by adding black bars on the sides (or top/bottom for portrait that is taller than 9:16). Crop fills the entire frame by trimming the edges. Use Pad when text or subjects sit near the edges; use Crop when the subject is centered and you want full-screen impact.
Are my videos uploaded anywhere?
No. Conversion runs in your browser via FFmpeg compiled to WebAssembly. After the page loads and the FFmpeg core file downloads once, no further outbound requests fire when you convert. Open DevTools → Network to confirm — your video bytes never leave the tab.
Does YouTube re-encode my upload anyway?
Yes, but giving YouTube the correct resolution and aspect ratio matters: an off-spec upload either gets letterboxed inside the Shorts player or rejected from the Shorts shelf entirely. Delivering 1080×1920 H.264 MP4 is what the recommended-upload spec calls for.
Why is the output always MP4?
MP4 with H.264 + AAC is YouTube's recommended Shorts upload format and works in every other vertical-video platform. Forcing this one output simplifies the workflow.
What about audio?
Audio is re-encoded to AAC at the chosen preset bitrate (96/128/160 kbps). Re-encoding is unavoidable because the source codec is rarely already AAC at a Shorts-friendly bitrate.
How long does conversion take?
Re-encoding video in WebAssembly is CPU-bound and runs at roughly 0.3 to 1 times realtime on a typical laptop. A 60-second source may need 1–3 minutes. The first conversion of the session also downloads the 30 MB FFmpeg core once; every subsequent conversion reuses the cached core.
How big a file can I convert?
Up to 4 GB per file. That ceiling matches the WebAssembly linear-memory limit per instance — the hard wall every in-browser FFmpeg tool hits. For very long sources, trim them to the Shorts length cap first with the Video Splitter & Joiner.