Local video compressor
Choose Smaller, Balanced, or Higher quality—or set a practical file-size limit. The workspace estimates the trade-off locally before a browser-supported encode is attempted.
Your video stays on this device. No upload, account, or server-side processing job.
Browser-local workspace
Choose one local MP4, M4V, MOV, or WebM file. JavaScript activates a browser-native preview and capability check; available conversions depend on the codecs supported by this device.
No upload, account, or server-side media job.
A size target must share its available bits across the full duration, video, audio, and container overhead. Very small limits can require a lower resolution or a shorter clip; a clear warning is more useful than silently creating an unusable file.
The compressor reopens the output and reports its real bytes, dimensions, duration, and codec facts. A requested bitrate or size is a plan, not proof, until the resulting file has been measured.
Private browser processing
Aftermath reads selected video bytes only in the current browser. Unsupported codecs are reported clearly rather than sent to another service. High-resolution conversion can use substantial device battery and processing.
Try a measured example
The Smaller setting reduced this synthetic clip while keeping its measured dimensions and duration. Download both copies to compare.
| Before compression · MP4 | Bytes: 17,835 Seconds: 1.012 Pixels: 640 × 360 |
|---|---|
| After compression · MP4 | Bytes: 10,386 Seconds: 1.012 Pixels: 640 × 360 |
This result changed from VP9 to H.264 inside MP4. Re-encoding an already small video can increase its size; check your own result.
Tested: · Chromium 149.0.7827.55
These files passed through the actual tool controls. Downloads were reopened to check sizes, duration, dimensions, or page structure. Capture used synthetic streams; hardware permissions were not tested.
These synthetic samples are free to reuse under CC0. No personal files or recordings were used. Your results may differ.
Use this route when the goal is a smaller copy of one local MP4, M4V, MOV, or WebM video. Choose a quality preset or practical size budget; the browser estimates a one-pass bitrate plan, performs a supported local encode, then reopens the MP4 result and reports its actual bytes and media facts. It does not promise an exact final size or send unsupported codecs to a server.
A 60-second local video needs a smaller MP4 using a quality preset rather than a guaranteed exact byte result.
Observed operation: Choose the compression plan, encode locally and reopen the completed MP4 to measure bytes, duration, dimensions and tracks.
Review the result: Play the full output, inspect motion and audio sync, and compare measured bytes with the intended ceiling.
Boundary: One-pass budgeting and browser codecs cannot promise exact bytes, lossless quality or compatibility with every destination.
Reduce one local video’s file size with a quality preset or one-pass size budget
The selected video stays in the current browser session and is not sent to an Aftermath processing service. How local processing is verified.
Checks the displayed limits and reports or creates a separately downloaded compressed MP4 with measured bytes and media facts from one selected local MP4, M4V, MOV, or WebM file.
Converting a compatible source to MP4 without a size goal belongs to /video/convert-to-mp4.
