MP4 · MOV · WebM · Mobile + Desktop · No Upload

Compress Video
Share Anywhere

Shrink MP4, MOV and WebM videos for WhatsApp, email and social media — right in your browser. Works on Android, iPhone and desktop. Nothing is ever uploaded to a server.

Up to 90%size reduction
5resolution options
Freeno account
Privateruns on your device
⚡ Real video compression: Powered by FFmpeg WebAssembly — the same engine used in professional video software. Any common format in, optimized MP4 out. Your file is processed locally and never leaves your device.
🎬
Drop your video here
MP4 · MOV · MKV · AVI · WebM · click to browse
Output Quality
Quality Medium
Resolution

How to compress a video online for free

This tool reduces the file size of MP4, MOV, AVI, MKV and WebM videos directly inside your browser, using a technology called FFmpeg WebAssembly. There is no upload step, no waiting in a server queue, and no watermark added to your video. It works equally well on a phone or a desktop computer.

STEP 1
Choose your video
Drag and drop a video file, or tap the box to select one from your phone or computer's storage.
STEP 2
Pick quality & resolution
Lower resolution gives the smallest file. 480p is ideal for WhatsApp, 720p for general sharing, 1080p for HD playback.
STEP 3
Compress and download
Tap Compress Video. When it finishes, download the smaller MP4 file directly to your device.

Best settings for common situations

Sending a video on WhatsApp: choose 480p resolution with Medium quality. This usually brings most videos under WhatsApp's 16MB sharing limit while keeping the video watchable on a phone screen.

Attaching a video to an email: choose 480p or 360p with the Smaller File quality preset, which keeps most clips under typical 25MB email attachment limits.

Posting to Instagram, TikTok or YouTube Shorts: 720p with Good quality offers a strong balance between file size and visual sharpness for social platforms.

Archiving or backing up a video: keep the Original resolution and choose a higher quality setting so detail is preserved while the file is still noticeably smaller than the source.

Tips for compressing video on mobile

Mobile browsers have less memory available than desktop computers, so very large video files can sometimes fail to process. For the smoothest experience on a phone, keep source videos under 150MB, choose 480p or 360p resolution, and avoid switching apps while compression is running. If a video does not finish processing, try again with a lower resolution.

Frequently asked questions

How do I compress a video for WhatsApp?+
Upload your video, select 480p resolution and the Medium or Smaller File quality preset. This usually brings a typical video under WhatsApp's 16MB limit. Download and send directly from your device.
Is my video uploaded to a server?+
No. All compression runs inside your browser using FFmpeg WebAssembly. Your video file stays on your device and is never transmitted anywhere.
Does this work on Android and iPhone?+
Yes, it works in modern Chrome and Safari on both Android and iPhone. For best results on mobile, keep files under 150MB and choose 480p or 360p resolution.
How much smaller will my video become?+
Most videos shrink by 50-90% depending on the original quality and the settings you choose. Large, high-bitrate source videos can sometimes shrink by up to 95-99% when reduced to 360p with the smallest quality setting.
What is the difference between resolution and quality?+
Resolution is the pixel dimensions (360p, 480p, 720p, 1080p). Lower resolution gives the biggest file size reduction. Quality controls how much detail is kept at that resolution — lowering it shrinks the file further with some loss of sharpness.
Why did compression fail or get stuck?+
This is usually caused by a video file that is too large for your device's available memory, or a browser that doesn't fully support the required features. Try a smaller video file, lower the resolution to 480p or 360p, or use a recent version of Chrome.
How long does video compression take?+
Compression time depends on your video length, resolution and your device's speed. A 10MB video at 480p typically takes 2–5 minutes in your browser. Longer or higher resolution videos take more time. The engine loads once and stays ready — subsequent compressions on the same page are faster.
What video formats are supported?+
MP4, MOV, AVI, MKV and WebM are all supported as input. The output is always MP4 (H.264), which is the most compatible format — it plays on every phone, computer, TV and platform without needing any special app or codec.
Which resolution should I choose?+
For WhatsApp and messaging apps, 480p gives the best balance of size and quality. For email attachments, 360p keeps files small enough for most email providers. For YouTube uploads and social media where quality matters, 720p or 1080p is recommended. For archiving personal videos, use Original to keep full quality while only reducing the bitrate.
What is CRF and how does it affect quality?+
CRF stands for Constant Rate Factor — it is the parameter that controls H.264 video quality. Lower CRF values mean higher quality and larger files. Higher CRF values mean lower quality and smaller files. The quality slider in this tool maps directly to CRF values optimized for each use case, so you do not need to set CRF manually.
Can I compress a video without losing quality?+
Truly lossless video compression produces very little file size reduction. In practice, the High or Excellent quality settings on this tool compress at a level where the difference from the original is not visible to the human eye on a phone or computer screen, while reducing file size by 30–50%. This is called visually lossless compression.
Why does the page say "Loading compression engine"?+
The first time you compress a video, the browser downloads and compiles the FFmpeg WebAssembly engine. This is a one-time process that takes 1–3 minutes depending on your connection speed and device. After the engine loads, it stays ready for the rest of your session — you do not need to wait again if you compress more videos on the same page.
What is FFmpeg WebAssembly?+
FFmpeg is the world's most widely used video processing engine — it powers YouTube, VLC, Handbrake and thousands of other applications. WebAssembly is a technology that allows complex software to run inside a web browser at near-native speed. CompressAll uses FFmpeg compiled to WebAssembly, which means professional-grade video compression runs entirely in your browser without any server.
Is there a maximum file size?+
There is no enforced file size limit. However, very large files (over 500MB) require a large amount of browser memory and may fail on devices with limited RAM, such as older phones. For files over 200MB, we recommend selecting 480p or lower resolution to reduce memory usage during processing.

Video compression tips — get the best results

Tip 1 — Match resolution to your intended use

The single biggest factor in video file size is resolution. A 1080p video contains four times as many pixels as a 480p video and will always be significantly larger at the same quality level. Before compressing, think about where the video will be watched. A video that will only ever be viewed on a phone screen does not need to be 1080p — 480p looks identical on a 6-inch screen and is four times smaller.

Tip 2 — Use 480p for WhatsApp and messaging

WhatsApp has a 16MB file size limit for video messages and compresses videos further when they are sent, which can reduce quality. Compressing your video to 480p before sending prevents WhatsApp from applying its own heavy compression. The result is a video that looks noticeably better than one sent uncompressed, because you control the compression rather than WhatsApp's automatic system.

Tip 3 — Keep audio bitrate at 128k for most uses

Audio takes up a surprisingly small portion of a video file — typically 5–15%. The 128kbps AAC audio setting used by this tool is transparent for most content — meaning the difference between 128kbps and the original audio is inaudible on phone speakers and standard headphones. Only reduce audio quality below 128kbps if you are compressing content where audio quality is not important, such as screen recordings or tutorial videos.

Tip 4 — For email, target under 25MB

Most email providers have a 25MB attachment limit. Gmail, Outlook and Yahoo all enforce this limit. To reliably send a video by email, compress it to under 20MB to leave room for the email headers and other attachments. Select 360p resolution and Medium quality — this combination typically produces files of 5–15MB for videos up to 3 minutes long.

Tip 5 — Keep the browser tab active during compression

Modern browsers pause or throttle JavaScript execution in background tabs to save battery and resources. If you switch to another tab or minimize the browser window during compression, the process may slow down significantly or pause entirely. Keep the CompressAll tab in the foreground and active while compression is running for the fastest results.

Understanding video file size — what makes videos large?

Video file size is determined by bitrate multiplied by duration. Bitrate is the amount of data used per second of video, measured in kilobits per second (kbps) or megabits per second (Mbps). A video recorded at 50 Mbps for 60 seconds produces approximately 375MB of data. Most smartphone videos are recorded at 15–50 Mbps, which is far higher than what is needed for watching on a phone or computer screen.

H.264 encoding — the standard used by this tool — is highly efficient at reducing bitrate while maintaining visual quality. A video that looks identical to a 50 Mbps source can often be encoded at 2–5 Mbps using H.264 with the right settings. This is why video compression can achieve 80–90% file size reduction while the video still looks good on screen.

The three main factors you control when compressing a video are resolution (pixel dimensions), quality (which controls bitrate), and audio bitrate. Reducing any of these reduces the output file size. Resolution has the biggest impact — reducing from 1080p to 480p alone can reduce file size by 70–80% before any quality adjustment.

Video compression for social media platforms

WhatsApp: Maximum 16MB for video messages. Use 480p, Medium quality. Videos under 3 minutes compress well under this limit at 480p.

Instagram Reels and Stories: Instagram recompresses uploaded videos to H.264 at around 3.5 Mbps. Upload at 1080p, High quality for best results — Instagram's recompression from a high-quality source looks better than compressing heavily before upload.

YouTube: YouTube accepts any file size and recompresses everything anyway. Upload the highest quality you have — there is no benefit to pre-compressing for YouTube uploads.

Twitter / X: Maximum 512MB and 2 minutes 20 seconds. 720p at High quality works well. Twitter recompresses to H.264, so providing a good source gives better final quality.

Email: Target under 20MB. Use 360p or 480p, Medium quality. For longer videos, consider sharing a link instead of attaching directly.

Telegram: No file size limit for Telegram Desktop. Telegram Mobile has a 2GB limit. No pre-compression needed for Telegram in most cases.

Privacy — why browser-based video compression matters

Most online video compressors require you to upload your video to their servers. This means your video — which may contain private moments, personal information or confidential content — passes through a third-party server. Even if the service deletes your video after processing, there is a window during which it exists on someone else's infrastructure.

CompressAll processes your video entirely inside your browser using FFmpeg WebAssembly. The video data never leaves your device. No upload happens. No third party ever receives your video. You can verify this by opening your browser's Network tab in Developer Tools while compressing — you will see no video data being transmitted over the network.

This approach is particularly important for videos containing children, private family moments, business presentations, legal proceedings, medical content or any other sensitive material. Browser-based processing gives you a privacy guarantee that server-based tools cannot match.