Compress a video
4K has four times the pixels of 1080p, and 8K sixteen times — so a short clip from a new phone arrives at hundreds of megabytes. Make it small enough to upload or email, without it looking cheap.
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 compressing works
At a glance
- Opens
- MP4, MOV (including iPhone HEVC), MKV and WebM
- Saves
- MP4, MOV or MKV — H.264 video, AAC audio
- Runs on
- Your computer, inside this tab (WebAssembly)
- Comfortable size
- Up to about 300 MB on a phone; more on a laptop
- Time
- About 1.2 minutes per minute of 1080p video; 4K takes roughly four times as long
- Quality
- Re-encoded once, at a bitrate chosen to hit your target size
How it works
A video file is its bitrate multiplied by its length. A phone spends that bitrate on pixels, and pixels add up fast: 4K carries four times the pixels of 1080p, 8K sixteen times. That is why a short clip from a new phone arrives at hundreds of megabytes.
Compress does two things. It scales the picture to the size people will actually watch it at — a phone screen is about 1080 pixels wide — and it re-encodes the video at a bitrate worked out from the size you ask for. The same minute ends up taking a fraction of the space, and on a phone screen it looks the same.
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 how smallKeep it sharp, Balanced or Smallest. Each fills in a suggested target size, which you can overwrite with any number.
- Pick size and format“Choose for me” stops at 1080p and never enlarges a video. MP4 plays everywhere; MOV and MKV are there when someone asks for them.
- Compress and downloadKeep the tab open while it works. When it is done, the file stays in this browser until you press Delete.
Which setting for which job
| If you are… | Choose |
|---|---|
| Posting to Reels, TikTok or Shorts | Balanced · 1080p · MP4 |
| Text on screen — a menu, a price list, slides | Keep it sharp · 1080p |
| Emailing or texting a preview | Smallest file · 720p |
| An upload form says “max 25 MB” | Type 25 into Target size — the tool aims 3% under it |
| Sending footage to Ruzz or another editor | Balanced · 1080p — vertical shorts are cut from 1080p |
| A 4K or 8K clip from a new phone | Choose for me — it scales to 1080p, which is far quicker and looks the same on a phone |
| Keeping the original for the archive | Do not compress — keep the file as filmed |
Under the hood
The technical detail, for anyone who wants to know exactly what happens to their file. Each line first says it plainly.
H.264 (AVC), encoded with libx264
The video format every phone, browser and TV plays.
Encoded with the veryfast preset: the encoder spends less time searching for motion between frames, trading a little efficiency for an encode that finishes in minutes inside a browser.
Target bitrate, with a VBV ceiling
Your target size is turned into a bitrate.
Video bitrate = target MB × 8,000 kbit × 0.97 ÷ seconds, minus 128 kbps for the sound. Peaks may reach 1.45× that and the buffer holds 2× (up to 16 Mbps), so busy scenes cannot blow through the target. The result stays between 120 kbps and 20 Mbps.
Resolution scaling
Fewer pixels, far fewer megabytes.
Scaled by height with the width left to follow, rounded to an even number (H.264 requires it), so the aspect ratio is exact. A video is never scaled up.
yuv420p — 4:2:0 chroma, 8-bit
The colour layout every player expects.
Brightness at full resolution, colour at a quarter — invisible to the eye at normal viewing, and the layout some phones and browsers insist on before they will play a file at all.
AAC audio at 128 kbps
Clear sound at about 1 MB a minute.
Stereo AAC at 128 kbps — also the minimum Instagram's published Reels ad specification asks for.
Fast start
Plays before it has finished downloading.
MP4 and MOV files carry an index (the moov atom); this moves it to the front, so a shared link or an upload preview can start playing at once.
Suggested target size
Why the number starts where it does.
The lower of two estimates: what this resolution usually needs — 6,000, 3,800 or 2,000 kbps at 1080p for Keep it sharp, Balanced and Smallest, scaled with pixel count — and 70, 45 or 28% of what your file already uses. The second stops the tool suggesting a “target” larger than a file that is already small.
WebAssembly, one thread
Your computer does the work.
ffmpeg is compiled to WebAssembly and runs on one CPU thread in this tab. The browser gives a page a fixed amount of memory; if a large 4K file runs out, the tool retries on its own as MP4 at 1080p.
Platform specs
What each platform accepts. Compressing to 1080p and MP4 fits all three; Instagram also takes up to 1440 × 2560 if you need the extra detail.
| 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 |
|---|---|---|
| “Needed more memory than the browser allows”, or the tab reloads | A large 4K or 8K file went past the memory a browser gives one page — most often on a phone. | Use a laptop, pick 1080p or lower, or trim the clip first. The tool already retries once as MP4 at 1080p. |
| It is taking a long time | The encode runs on a single CPU thread, and 4K has four times the pixels of 1080p. | Use “Choose for me” (1080p). Keep the tab open — closing it stops the job. |
| Colours look washed out after compressing an iPhone clip | The iPhone filmed in HDR. This tool writes standard-dynamic-range video and does not convert HDR brightness, so the brightest colours can look flat. | For clips you plan to post, turn off Settings › Camera › Record Video › HDR Video — or post the original if it is under the platform's size limit. |
| The file barely got smaller | The source was already efficient — iPhone HEVC files are compact — so most of the saving has to come from resolution. | Pick 1080p or 720p, or choose Smallest file. |
| An upload form still says the file is too large | The form's limit is below the target you typed, or it counts megabytes differently. | Type a target a little under the limit. The tool aims 3% under whatever you enter and uses decimal megabytes, as most forms do. |
Privacy: your file stays on your computer
Compressing a 4K clip means reading hundreds of megabytes. Doing it in your browser means none of it travels anywhere — no upload wait, and no copy of your footage on anyone's server.
- 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
Is my video uploaded anywhere?
No. The compression runs inside your browser using WebAssembly. The file stays on your computer, and there is nothing for us to store or delete.
How much smaller will it get?
It depends on the source, but at Balanced a minute of 1080p comes to about 29 MB. A minute of 4K straight from a phone is usually many times that.
Does compressing lower the quality?
Some detail is traded for size — that is what compression is. At Keep it sharp or Balanced, at 1080p, the difference is hard to see on a phone. Smallest file is for previews, not for posting.
Should I compress 4K to 1080p or keep 4K?
For anything you will post, 1080p. Platforms re-compress what they receive, so 4K costs you time and upload data for detail few viewers will see. Keep 4K for archiving, a large screen, or when you plan to crop in afterwards.
Why is there no WebM option?
The WebM encoders a browser can run fail on real phone recordings, so we would rather not offer it than hand you a broken file. WebM files open here fine; they are saved as MP4, MOV or MKV.
Can I compress several videos at once?
One at a time. The finished file stays in this browser until you delete it, so you can start the next one straight after.
Does it work on a phone?
Yes, in a current browser. Phones give a page less memory, so keep files under about 300 MB there, or use a laptop for anything bigger.
Is there a limit on how often I can use it?
No. Nothing runs on our servers, so there is no quota, no watermark and no sign-up.
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
Convert format
Will not play or upload? Turn an iPhone MOV/HEVC, WebM or MKV into an MP4. Often seconds, with no quality loss.
Crop to 9:16
Turn a landscape or square video into a vertical short for Reels, TikTok and Shorts.
Trim video
Cut the dead air off the start and end, or keep just the 30 seconds that matter.
Extract audio
Pull the sound out of a video as MP3, WAV or AAC.
Grab a cover frame
Pick any moment and save it as a vertical cover image.
Join clips
Filmed it in three takes? Put them end to end in one video — different shapes and silent clips are fine.
Video to GIF
Turn a moment into a GIF with real colours, not the grainy web palette.
Compress image
Shrink and resize a photo to JPG, WebP or PNG. Instant.
Change speed
Slow motion or sped up, from 0.5× to 2×, with voices at their own pitch.
Remove sound
Take the audio off a video in seconds, picture untouched — then add a trending sound in the app.
Resize video
Exactly 1080×1920, 1080×1350, 1080×1080 or 1920×1080 — the size each platform asks for.