Compress MP4 Video
Reduce the file size of your MP4 videos by optimizing codec, quality, and resolution while maintaining visual quality.
Compress MP4 files online, free, no account needed
SimpleSize encodes your MP4 at a lower bitrate and, optionally, a smaller resolution, then returns a new MP4 file that plays on the same devices as the original. The output container is always MP4, so nothing downstream breaks. Processing happens on the server, not in your browser, which means large files complete reliably regardless of your device.
Files up to 1 GB are accepted. No login is required, and you can process up to 10 videos per day.
Why reducing MP4 file size matters
Video files consume storage, bandwidth, and upload time in ways that other formats do not. A 500 MB recording can exceed email attachment limits, slow a website, or fail to upload to a platform with a size cap. Knowing how to reduce MP4 file size gives you control over those constraints without re-shooting or re-editing.
- Sharing over messaging apps or email where attachment limits apply
- Uploading to platforms that enforce a maximum file size
- Saving storage on a phone, drive, or cloud account
- Reducing page-load time when a video is embedded on a website
- Sending project files to collaborators on slow connections
For a deeper look at why video bitrate drives file size, see the video bitrate explained guide.
How the compression works
When you upload an MP4, the tool re-encodes the video stream using the codec and quality settings you choose. The quality slider controls the target bitrate as a percentage of the original (10% to 100%, default 70%). Lowering that percentage tells the encoder to discard more data per frame, which shrinks the output at the cost of some visual detail.
Choosing a more efficient codec can reduce MP4 size further without dropping quality as aggressively. H.265 encodes the same visual information in roughly half the data compared with H.264, though it takes longer to process. VP9 and AV1 are strong alternatives for web use. H.264 remains the safest choice for broad device compatibility.
Selecting a lower target resolution, such as 720p or 1080p, scales the frame dimensions down before encoding, which reduces the number of pixels per frame and further decreases mp4 file size. If your video will only ever be watched on a phone screen, 1080p is often indistinguishable from the original 4K source.
How to compress an MP4: Step-by-step
- Open the tool at simplesize.app/en/compress-mp4 and drag your file onto the dropzone, or click to browse your device.
- Wait for the upload to finish. A progress indicator confirms when the file is ready.
- Choose a codec. H.264 gives the widest compatibility; H.265 gives smaller files at similar quality but processes more slowly.
- Adjust the quality slider. The default of 70% balances file size and visual quality for most use cases. Move it lower to shrink the file further.
- Optionally select a target resolution if you want to scale the video down (for example, 1080p or 720p).
- Click "Compress Video" and watch the progress bar, which shows current time, total duration, time remaining, and percent complete.
- When processing finishes, review the results: original size, compressed size, savings percentage, codec used, and bitrate. Download your file. The download link is available for 300 seconds.
Uploaded files are processed on the server and not retained beyond the session. Your download link expires after 300 seconds, after which the file is removed.
Codec comparison: Which to pick
The codec you choose determines how the encoder compresses each frame. Different codecs use different mathematical models to represent motion and color, which is why they produce different file sizes at the same perceived quality.
- H.264: Widest device and platform support. Good compression for its age. Best default if you are unsure where the video will be played.
- H.265: Roughly 40 to 50% smaller than H.264 at equivalent quality. Slower to encode. Some older devices do not support playback.
- VP9: Open format with strong compression. Well supported in browsers. Good for web delivery.
- AV1: The most efficient codec available here. Produces the smallest files but takes the longest to process.
- VP8: Older open format. Useful when VP9 compatibility is uncertain.
If you want to understand codec differences at a technical level, the what is a codec article covers the mechanics in detail.
When to use this tool vs. other formats
This tool is scoped to MP4 input and output. If your source file is in a different container, use the matching tool instead. The video compressor accepts multiple formats and lets you choose the output container. For MOV files specifically, the compress MOV tool handles that workflow directly.
If your goal is to change the container or codec without prioritizing size reduction, the video converter is a better starting point.
FAQ
Yes. Compressing videos here is free with no account required. The daily limit is 10 videos per IP address, resetting at midnight UTC. This limit is shared across video compression and video conversion on the same IP. There are no paywalls, watermarks, or subscription tiers for the compression output.
The upload limit is 1 GB per file. Files larger than that cannot be processed. If your source file exceeds 1 GB, consider trimming it in a video editor before uploading, or exporting a lower-resolution version from your editing software first to bring it under the limit.
Processing is server-side. Once compression finishes, a download link is generated and remains active for 300 seconds. After that window closes, the file is deleted from the server. Your source file is not retained beyond the session. If you miss the download window, you will need to re-upload and compress again.
AV1 produces the smallest output at equivalent quality because it uses the most advanced compression model available in this tool. H.265 is a practical middle ground: it cuts file size by roughly 40 to 50% compared with H.264 while processing faster than AV1. If playback compatibility on older devices is a concern, H.264 is the safest choice even though it produces larger files.
The default of 70% targets a bitrate at 70% of the original. This preserves noticeable detail for most content while meaningfully reducing file size. For talking-head videos or screen recordings with limited motion, you can often go as low as 50% without visible degradation. For high-motion sports or cinematic footage, staying at 65 to 80% avoids blocking artifacts in fast-moving areas.
Yes, resolution has a large impact because it controls the total number of pixels per frame. Scaling a 4K (2160p) video down to 1080p reduces the pixel count by 75%, which significantly lowers the data the encoder needs to represent each frame. Combining a resolution reduction with a lower quality setting produces the greatest decrease in MP4 file size, though at the cost of spatial detail.
This tool accepts only MP4 input and always outputs MP4. The general video compressor accepts multiple container formats (MKV, MOV, WebM, and others) and lets you choose a different output container. At the encoding level both tools apply the same re-encoding process: they read the source stream, apply the selected codec and quality settings, and write a new file. The difference is in which containers are accepted and returned.
Yes, but the gains diminish with each generation of compression. When a video has already been encoded at a low bitrate, re-encoding it introduces generation loss: the encoder tries to compress data that was already reduced, and artifacts from the first pass get amplified. If the source is already heavily compressed, lowering quality further will produce visible blocking or blurring rather than a clean smaller file.
The tool re-encodes the video stream according to your settings. The audio stream is included in the output MP4. Audio bitrate is not separately configurable in this tool. For most use cases the audio output is acceptable, but if precise control over audio bitrate or format is required, a dedicated audio workflow would be more appropriate.
This can happen when the source video was encoded at a very low bitrate to begin with. If you set the quality slider above the effective bitrate of the original, the encoder may produce a file with a higher bitrate than the source. To avoid this, keep the quality slider at or below 70% when working with files that are already small relative to their duration and resolution.
Yes. Because processing is server-side rather than in-browser, the tool does not depend on your device's CPU or GPU. You upload the file, configure the settings, and the server handles encoding. This means a phone with limited processing power can compress a large video just as effectively as a desktop computer. The upload speed of your connection is the main variable that affects how long the process takes.
SimpleSize has dedicated tools for other video containers. The compress MKV tool handles Matroska files, and there are separate tools for MOV, WebM, and others. For images, tools cover JPG, PNG, WebP, AVIF, HEIC, GIF, and TIFF. All tools follow the same pattern: the output container matches the input container, and no account is required.