Video Format Converter for WebM to MP4, MP4 to WebM, and Browser FFmpeg
Convert WebM to MP4 or MP4 to WebM locally with quick presets, quality, resolution, and audio controls. The FFmpeg engine is hosted with the site, loads only when you start processing, and this browser-side version is best for short clips under 200MB.
Ready to use
Browser-side · no account · results stay on this page
Drop video here or click to upload
MP4 and WEBM are the safest first-version inputs.
Max file size: 200MB
No video uploaded
Mobile processing guidance
On mobile, start with a short MP4/WebM under 50MB before trying larger clips.
Max 200MB in this browser version.
FFmpeg uses this tab's CPU and memory after you start processing.
If processing stalls, stop and retry with a shorter clip, lower resolution, or higher CRF.
File limit
Use files under 200MB. Smaller clips are more reliable on mobile.
Processing time
FFmpeg loads after you click the action button, then uses local CPU and memory.
Common failures
Unsupported codecs, low memory, very large files, or long clips can fail.
Quick conversion presets
Start from the target player or upload surface, then adjust quality, resolution, or audio.
Output MP4
H.264 video with AAC audio for broad compatibility.
Keep the source dimensions.
Disable for a smaller silent video.
Engine
ffmpeg.wasm
Output
MP4
Audio
128 kbps
Frame rate
Source FPS
Next step
Choose a short MP4 or WebM first. On mobile, start under 50MB before trying larger clips.
Output size
No converted video yet
Format
MP4
Size change
Not ready
FFmpeg is designed to run in the browser only after you start processing, and the large WebAssembly engine is served from this site.
A video format converter re-encodes a source video into a different browser-friendly output format.
This first version focuses on MP4 and WebM because they cover the most common web publishing, upload, sharing, and browser playback needs.
Use the quick presets to choose WebM to MP4 compatibility, MP4 to WebM playback, mobile upload MP4, silent web preview, or a GIF-like silent WebM clip before adjusting quality manually.
FFmpeg loads only when you start processing; large files, unsupported codecs, and mobile browsers can still run into memory limits, so use desktop for larger clips.
Short clips under 200MB
MP4, WEBM, MOV, and other common containers are the best first inputs for this browser-side conversion flow.
Destination format choice
Choose MP4 for broad compatibility, WebM for modern browser playback, or a mobile upload preset when the destination has stricter file expectations.
GIF-like web snippets
Use the silent WebM 480p preset when you need a tiny loop-style clip instead of a heavier GIF.
Mobile and slower devices
Use shorter clips or lower resolution on mobile because ffmpeg.wasm conversion can be memory intensive.
Desktop for large clips
If the source is long, high resolution, or near 200MB, use a desktop browser or desktop video software before retrying.
WebM to MP4 upload
Convert a browser recording to a format accepted by more upload forms.
Input
A WebM screen recording exported from a browser tool.
Settings
- Preset: MP4 compatibility
- Keep audio
- Original resolution
Expected output
An MP4 file with broader upload compatibility.
MP4 to WebM embed
Create a browser-first WebM version for a web page preview.
Input
A short MP4 product clip.
Settings
- Preset: WebM web playback
- Quality: balanced
- Limit resolution to 1080p
Expected output
A WebM output ready to test in browser playback flows.
GIF-like WebM
Make a silent loop-style clip when GIF would be too heavy.
Input
A short MP4 animation snippet.
Settings
- Preset: GIF-like web clip
- Remove audio
- Width: 480px
Expected output
A small silent WebM that can replace a heavier GIF.
Know the upload target
Choose MP4 for broad upload support and WebM for browser-native playback before changing quality settings.
Check size and duration
Files over 200MB are rejected in this version, and long high-resolution clips are better handled on desktop.
Expect re-encoding
Conversion creates a new file; it can change codec, audio behavior, metadata, and file size.
Use desktop for heavy files
Mobile browsers are best for short tests. Move long, 4K, or near-limit files to a desktop workflow.
Choosing a format without a target
Pick the destination first: upload form, chat app, browser page, mobile preview, or documentation embed.
Expecting every codec to decode
FFmpeg supports many formats, but browser memory and WebAssembly limits still matter. Common MP4 and WebM inputs are safest.
Treating all failures the same
Codec unsupported, memory limit, file too large, and long high-resolution clips need different retries.
Confusing conversion with compression
Changing container format does not guarantee a smaller file. Use the video compressor when file size is the main goal.
Ignoring destination support
Use MP4 for broad compatibility and WebM for browser-native workflows. Test the final platform before publishing.
Compatibility
Convert WebM or MOV clips to MP4 before uploading to systems that expect MP4.
Browser workflows
Convert MP4 to WebM when a browser-native delivery format is preferred.
Mobile uploads
Use an MP4 output preset with a practical resolution when a phone-first platform rejects the original file.
Preview exports
Create a smaller preview version while keeping the original source file private.
GIF-like web clips
Export a silent 480p WebM when a tiny loop-style product or documentation preview is better than GIF.
Local testing
Test MP4 and WebM behavior with browser-side processing for this tool.
webm to mp4 converter
Use MP4 compatibility when a WebM recording needs to upload to a wider range of apps.
mp4 to webm
Use WebM output when the destination is a browser-first page or preview workflow.
gif like video clip
Use the silent WebM 480p preset when you need a small loop-style clip instead of an animated GIF.
convert video in browser
Use the local FFmpeg workflow for short clips when you want to avoid opening a desktop editor.
video codec unsupported
Retry with common MP4/WebM input, original resolution, or a desktop workflow when browser conversion fails.
Input/output matrix
Use WebM to MP4 for compatibility, MP4 to WebM for browser playback, and GIF-like WebM for silent short previews.
Processing stages
The tool loads FFmpeg, writes the source file, converts locally, reads the output, then creates a downloadable file.
Failure explanations
Unsupported codecs, low memory, files near 200MB, and long high-resolution clips are separate failure modes.
Use desktop for large files
Desktop browsers and desktop video tools are more reliable for long, 4K, or near-limit conversion jobs.
Audio choice matters
Removing audio can make preview clips simpler, but keep audio when the destination needs narration or sound.
Compression is separate
Use the compressor when the primary goal is a smaller file, not just a different format.
How is the video converted?
The selected video is designed to be processed in your browser with ffmpeg.wasm based on the current public implementation. Avoid sensitive files unless you have reviewed the implementation.
Which output formats are supported?
The first version supports MP4 with H.264/AAC and WebM with VP9/Opus, which are practical browser-side output formats.
What preset should I start with?
Use MP4 compatibility for broad uploads, WebM web playback for browser-first pages, mobile upload MP4 for smaller social or CMS uploads, silent web preview when audio is unnecessary, and GIF-like web clip for tiny loop-style snippets.
Can it convert every video format?
No. FFmpeg can read many containers, but browser memory, codec support, and WebAssembly limits still matter. Use smaller files and common inputs for the best result.
Why did conversion fail?
Common causes are an unsupported source codec, not enough browser memory, a file near the 200MB limit, or a long high-resolution clip. Retry with a shorter file, original resolution, MP4/WebM input, or a desktop browser.
Is conversion the same as compression?
No. Conversion changes the output format or codec. Compression focuses on reducing size with quality, resolution, and bitrate choices.
How is the video converted?
The selected video is designed to be processed in your browser with ffmpeg.wasm based on the current public implementation. Avoid sensitive files unless you have reviewed the implementation.
Which output formats are supported?
The first version supports MP4 with H.264/AAC and WebM with VP9/Opus, which are practical browser-side output formats.
What preset should I start with?
Use MP4 compatibility for broad uploads, WebM web playback for browser-first pages, mobile upload MP4 for smaller social or CMS uploads, silent web preview when audio is unnecessary, and GIF-like web clip for tiny loop-style snippets.
Can it convert every video format?
No. FFmpeg can read many containers, but browser memory, codec support, and WebAssembly limits still matter. Use smaller files and common inputs for the best result.
Why did conversion fail?
Common causes are an unsupported source codec, not enough browser memory, a file near the 200MB limit, or a long high-resolution clip. Retry with a shorter file, original resolution, MP4/WebM input, or a desktop browser.
Is conversion the same as compression?
No. Conversion changes the output format or codec. Compression focuses on reducing size with quality, resolution, and bitrate choices.
Suggested workflow
Build a browser-side video conversion workflow
Convert the source format, compress when needed, then extract a cover image for publishing.
Guides and examples