Do not re-encode a compatible MOV by default
A MOV with compatible H.264 video and AAC audio can often move to an MP4 container while retaining its media packets. That preserves quality and is much faster than decoding the whole clip.
Local MP4 converter
Convert a supported video to MP4
Inspect the selected video first. Compatible H.264 video and AAC audio can be remuxed into MP4 without re-encoding; other tracks may need a browser-supported local conversion.
Your video stays on this device. No upload, account, or server-side processing job.
Browser-local workspace
Choose a local video to begin.
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.
The local workspace loads after you choose a video.
Keep advanced choices out of the way
The basic choice is an MP4 output with maximum compatibility or a smaller-file preference. A remove-audio option belongs in this same converter because it can be a packet-copy operation when the output container remains compatible.
Private browser processing
Your video remains in your hands.
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.
How to use this tool
Convert a supported local MP4, M4V, MOV, or WebM video to a separate MP4 in this browser. The worker inspects tracks, reuses compatible MP4 data when possible, or performs a browser-supported local encode, with optional audio removal. The reopened result reports its tracks and file facts before download. This route targets MP4 compatibility, not an exact size, time range, crop, or universal codec guarantee. One completed output is limited to 500 MB in browser memory.
What to choose and what you get
What to choose
- one selected local MP4, M4V, MOV, or WebM file
Result
- a separately downloaded MP4 with the completed tracks reopened and checked
Supported use
- One readable local MP4, M4V, MOV, or WebM source that needs an MP4 output.
- Compatible video and audio tracks that can use the local MP4 conversion path without an unnecessary re-encode.
- Maximum-compatibility or smaller-file encoding preferences, with optional audio-track removal.
Before you start
- Output containers other than MP4 or a promise that every MOV can be remuxed without quality change.
- Exact size targeting, time-range editing, frame cropping, or a remote codec-conversion fallback.
Supported formats
- Accepted formats: MP4, M4V, MOV, WebM.
- Output formats: MP4.
Browser support and permissions
- Modern browser with JavaScript and support for the selected media container and codec; memory and performance vary by device. Output operations keep one completed result in browser memory and are limited to 500 MB; read-only inspection can handle larger accepted sources up to 4 GB.
- No camera, microphone, or screen permission is needed.
Choose the right settings
- Use this route when the destination requires MP4 and the source tracks should be retained when compatible.
- Use /video/compress for a byte-size goal, /video/trim for a kept range, or /video/crop for a new frame.
- Use /video when the desired video outcome is still undecided.
- Review the reopened MP4 before replacing or submitting the source.
Worked example
A supported MOV needs an MP4 copy for compatibility, but reducing file size is not the primary goal.
Starting facts
- The source container and tracks are readable locally.
- Compatible tracks may be reused before re-encoding is considered.
Observed operation: Create an MP4 through the available local path and reopen the result to verify the expected completed tracks.
Review the result: Play the output, compare duration, dimensions, audio sync and track facts with the source before delivery.
Boundary: An MP4 container does not guarantee every player supports its codecs, profile, color, captions or metadata.
What you can do
Create an MP4 from one supported local video, preferring compatible track reuse before re-encoding
Choose another tool when
- Reducing a video toward a file-size budget belongs to /video/compress.
- Changing duration or frame composition belongs to /video/trim or /video/crop.
- This route creates MP4 only; it is not an arbitrary video-format converter.
If it does not work
- A container with no readable primary video track cannot produce the required MP4 video result.
- Incompatible tracks fail when this browser lacks the decoder or H.264/AAC encoding path needed for conversion.
- The result is withheld if the written MP4 cannot be reopened or contains tracks that contradict the selected options.
Things to know
- Codec support, performance, and memory use vary by browser, device, source, and operation.
Privacy boundary
The selected video stays in the current browser session and is not sent to an Aftermath processing service. How local processing is verified.
What this tool verifies
Checks the displayed limits and reports or creates a separately downloaded MP4 with the completed tracks reopened and checked from one selected local MP4, M4V, MOV, or WebM file.
Check before sharing
Reducing a video toward a file-size budget belongs to /video/compress.