Resize a video
Upload forms, ad managers and some schedulers ask for an exact pixel size. Get the file to that size — with bars, or filled edge to edge.
Everything happens inside your browser, using your own computer’s memory. Your file is never uploaded, never stored, and nothing is sent to us — so there is no limit on how often you use this.
How resizing works
At a glance
- Opens
- Any video your browser can read — MP4, MOV, WebM, MKV
- Saves
- MP4 at exactly the size you pick
- Sizes
- 1080 × 1920, 1080 × 1350, 1080 × 1080, 1920 × 1080
- Two ways
- Bars (keeps everything) or fill (crops the edges)
- Small videos
- Enlarged to the exact size — no sharper, but the right size
- Quality
- Re-encoded once at CRF 23
How it works
Upload forms, ad managers and scheduling tools often ask for one exact pixel size rather than a shape. A clip that is the right shape but the wrong size — 720 × 1280, or 608 × 1080 after a crop — can still be rejected.
Resize produces exactly the size you pick. If your video's shape matches, it is simply scaled. If it does not, you choose: bars keeps the whole picture and adds black where it does not reach; fill zooms in until there is no spare space and cuts off what hangs over the edges.
Step by step
- Drop the videoIt opens in this tab. Nothing uploads. The first time, the browser downloads the 32 MB video engine and keeps it.
- Pick the sizeThe line under the buttons shows your video's size, so you can see how far it is from the target.
- Bars or fillLeave “Fill the frame” off to keep everything; tick it to fill edge to edge and lose the edges.
- Resize and downloadKeep the tab open while it works. The file stays in this browser until you press Delete.
Which setting for which job
| If you are… | Choose |
|---|---|
| A form asks for 1080 × 1920 for Reels, TikTok or Shorts | 1080 × 1920 |
| An Instagram feed post that takes the most screen | 1080 × 1350 |
| A square ad placement or grid post | 1080 × 1080 |
| YouTube or a website, landscape | 1920 × 1080 |
| The picture must not lose anything | Bars |
| The subject is in the middle and the edges do not matter | Fill the frame |
| A sideways clip for a vertical post | Crop to 9:16 with its blurred backdrop first, then Resize |
Under the hood
The technical detail, for anyone who wants to know exactly what happens to their file. Each line first says it plainly.
Fit and pad (bars)
All of the picture, black around it.
The video is scaled until it fits inside the target (force_original_aspect_ratio=decrease), then padded with black to the exact size, centred. Wider pictures get bars above and below; taller ones at the sides.
Cover and crop (fill)
Edge to edge, edges lost.
The video is scaled until it covers the target (force_original_aspect_ratio=increase), then cropped to size from the centre.
Square pixels
Displays at the size it says.
setsar=1 marks every pixel as square, so players and upload checks read the size exactly as written.
Upscaling
Bigger is not sharper.
A smaller video is enlarged to the target to meet the required size. Enlarging cannot add detail that was not filmed; it only makes the numbers match.
libx264 at CRF 23
Rebuilt at the new size.
Every frame is re-encoded as H.264 with the veryfast preset at constant-quality CRF 23, 8-bit 4:2:0 colour, sound as AAC at 128 kbps, index moved to the front.
Platform specs
What each platform publishes about size. 1080 × 1920 is the common target for all three; Instagram also accepts up to 1440 × 2560.
| Platform | Shape | Resolution | File size | Length | Format |
|---|---|---|---|---|---|
| Instagram Reels | 9:16 | 1440 × 2560 recommended | Up to 4 GB | Up to 15 minutes | MP4 or MOV · H.264 · AAC stereo, 128 kbps or more |
| TikTok | 9:16 recommended | 540 × 960 or larger | Up to 500 MB | — | MP4, MOV, MPEG, 3GP or AVI |
| YouTube Shorts | Vertical or square | — | — | Up to 3 minutes | — |
From each platform's own published specifications (Meta Ads Guide, TikTok Ads video specifications, YouTube Help), checked September 2026. “—” means the platform does not state it. Platforms change these; check before a big campaign.
If something goes wrong
| What you see | Why | What to do |
|---|---|---|
| The result looks soft | A small video was enlarged to the target size. | Enlarging cannot add detail. Use the largest original you have, or film at 1080p or above. |
| Black bars I did not want | The video's shape does not match the target and bars keep everything. | Tick “Fill the frame”, or use Crop's blurred backdrop for a vertical post. |
| The edges of the picture are gone | Fill crops whatever hangs over the target's shape. | Untick “Fill the frame” to keep everything with bars. |
| It takes a long time | Every frame is re-encoded on one CPU thread, and 1080 × 1920 is a lot of pixels. | Trim first so there is less to resize, and keep the tab open. |
Privacy: your file stays on your computer
Your video is resized in your browser, on your computer. Nothing is uploaded.
- What your browser downloads
- The page — and, the first time you use a video tool, the video engine: about 32 MB, then kept in your browser's cache.
- What it sends to us
- Nothing. There is no upload step, no copy on our servers and no account. The work happens in your computer's memory.
- How we know
- Our automated tests run every tool while recording every network request the page makes. A single upload fails the test.
- Where the result lives
- In this browser only, until you press Delete. A finished file is still here if you close the tab and come back; a job still running stops when the tab closes.
Questions
How is this different from Crop to 9:16?
Crop keeps your video's own resolution, so a 1080p sideways clip becomes 608 × 1080. Resize makes it exactly the size you pick, such as 1080 × 1920.
Will a small video look sharper?
No — making a video larger cannot add detail that was not filmed. It only meets the size an upload form requires.
Which size for Reels, TikTok and Shorts?
1080 × 1920 works for all three.
Is my video uploaded?
No. It is resized in your browser, using your computer's memory.
A tool makes a file fit. It does not make people watch to the end — that is the hook, the order of the shots, the captions and the music. See how Ruzz does it.
Other free tools
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Crop to 9:16
Turn a landscape or square video into a vertical short for Reels, TikTok and Shorts.
Trim video
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Extract audio
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Grab a cover frame
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Join clips
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Video to GIF
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Change speed
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Remove sound
Take the audio off a video in seconds, picture untouched — then add a trending sound in the app.