FFmpeg Onlion — All Video Processing Runs in Your Browser
Powered by WebAssembly, FFmpeg Onlion brings the full power of FFmpeg into your browser. Format conversion, video compression, GIF creation, subtitle embedding — 30+ operations, all processed locally. No uploads, no accounts, just open the page and go.
Unlike traditional online video tools, FFmpeg Onlion keeps all processing on your device — fast, private, and secure.
100% Local Processing
FFmpeg Onlion is built on ffmpeg.wasm. Every video file is processed entirely inside your browser. Nothing is ever uploaded to any server — your videos stay on your device, eliminating any risk of data leaks.
30+ Operations in One Place
From format conversion, compression, and trimming to GIF creation, subtitle embedding, and audio extraction — FFmpeg Onlion covers virtually every video task you will need.
Operation Chaining + Batch Processing
FFmpeg Onlion lets you chain multiple operations into a single pass — one encode, zero quality loss from repeated re-compression. Batch mode handles multiple files in one go.
No Install Required
FFmpeg Onlion is a pure web app — just open your browser. After the initial ~31 MB WebAssembly core download, everything works completely offline.
Full Raw FFmpeg CLI Access
Beyond the visual interface, FFmpeg Onlion offers a raw command-line mode. If you know FFmpeg, just type your arguments directly — as flexible as the desktop version.
Broad Format Support
Output to MP4, WebM, MKV, MOV, AVI, and GIF for video; MP3, AAC, WAV, OGG, and FLAC for audio — all the formats you use every day.
How to Use FFmpeg Onlion
Three simple steps. No account needed, no software to install.
1
Load the FFmpeg Engine
Click "Load ffmpeg" on your first visit. The browser downloads the WebAssembly core (~31 MB) once, then works offline forever.
2
Choose a Video File
Drag and drop or click to select a video file. FFmpeg Onlion shows a preview and basic info — your file never leaves your computer.
3
Pick an Operation and Process
Choose from 30+ operations or chain several together, hit process, and download the result — all in your browser.
FFmpeg Onlion Video Processing Tool
Below is the complete FFmpeg Onlion tool panel. Every operation runs locally in your browser.
ffmpeg not loaded — click "Load ffmpeg" to begin
Input Video
Click to choose or drag & drop local file
MP4, WebM, MOV, AVI, MKV, GIF…
0 files queued
Trim applied to all operationsDisabled (batch mode)
Drag the handles to set start and end. Leave untouched to keep the full video.
0:00.0
0:00.0
0:00Full duration--:--
Operations
Convert to format
Use the Output Format selector below to choose format.
Resize & Compress
28(18=best · 28=default · 51=worst)
Dimensions are filled from the source video. Clear a field or set to -1 to preserve aspect ratio. Lower CRF = higher quality.
Extract audio track
Remove audio track
Output will be the same video with the audio stream stripped.
Animated GIF
Height is calculated automatically to preserve aspect ratio.
Playback speed
Rotate / Flip
Crop
Load a video to crop.
Load a video to preview the crop area.
Drag the box to move it. Drag the handles to resize.
Extract Thumbnail
Extracts a single frame at the given timestamp as an image file.
Reverse
Plays video and audio backwards. The whole clip is buffered in memory — keep clips under ~2 minutes for best results.
Fade In / Out
Set either value to 0 to skip that direction. Applied after trimming.
Adjust
0
1
1
Strip Metadata
Removes all embedded metadata (GPS, camera info, creation date, etc.) from the output file. Video and audio are re-encoded.
Embed Subtitles
No file chosen
Soft subtitles are the preferred format for VLC, browser players, and most video platforms. Hard-burning for social media requires a libass build.
Volume
1.0 = original · >1 = boost · <1 = reduce · 0 = silence. Audio is re-encoded; video is stream-copied.
Loop / Repeat
Streams are copied without re-encoding. The clip plays N times back-to-back. Trim is ignored for this operation.
Logo / Image Overlay
No file chosen
PNG with alpha gives cleanest results. Video is re-encoded to preserve overlay.
Mix Audio (Background Music)
No file chosen
Music loops automatically if it is shorter than the video. Video is stream-copied.
Concatenate (Join Clips)
No file chosen
Uses the concat filter — different resolutions and codecs are handled by re-encoding to H.264/AAC. Trim applies to the first clip only.
Side by Side
No file chosen
Both clips are scaled to the same height (horizontal) or width (vertical) then stacked. Re-encodes to H.264/AAC. Trim is ignored.
Picture in Picture
No file chosen
Overlay video loops if shorter than the main clip. Audio from the main clip is preserved. Trim applies to the main clip.
Media Info
Load a video file to see its properties.
Click Process Video to run a deep scan and log full codec & stream details below.
Raw FFmpeg
► Example Commands
No file chosen
--
Args are split on whitespace. Wrap values containing spaces in double quotes, e.g. -vf "scale=1280:-2,hflip"
Pad to Aspect Ratio
Video is scaled down to fit; empty space is filled with the chosen color. Re-encodes to H.264.
Normalize Audio (EBU R128)
Uses the loudnorm filter. Video stream is copied without re-encoding.
Denoise (hqdn3d)
Applies spatial + temporal noise reduction via hqdn3d. Higher strength = smoother but softer image.
Boomerang
Plays the clip forward then immediately in reverse — classic boomerang loop. Trim is respected. Audio is removed from the output.
Sharpen / Blur
Sharpen uses unsharp; blur uses boxblur. Audio is copied.
Operation Stack
No operations yet — configure an op above and click “Add to Stack”.
(stack is empty)
Operations run in the listed order as one filter chain with a single re-encode. Trim (if set) is applied first.
Estimated output size—
Processing…0%
Output ready:
Output
Process a video to see the result here
Batch Outputs (0)
FFmpeg Log
Ready. Load ffmpeg to begin.
Frequently Asked Questions About FFmpeg Onlion
Everything you might want to know before using FFmpeg Onlion.
How is FFmpeg Onlion different from traditional online video tools?
Most online video tools require you to upload files to a remote server for processing. FFmpeg Onlion is fundamentally different — it uses WebAssembly to run the full FFmpeg engine directly in your browser. Every operation happens locally on your device. Nothing is ever uploaded, no account is required, and no software needs to be installed. For anyone who values privacy and efficiency, FFmpeg Onlion is the safer choice.
What video formats does FFmpeg Onlion support?
FFmpeg Onlion accepts all common video formats as input, including MP4, WebM, MOV, AVI, MKV, and animated GIF. For output, it supports MP4 (H.264 + AAC), WebM (VP9 + Opus), MKV, MOV, AVI, and GIF for video; MP3, AAC, WAV, OGG, and FLAC for audio. Essentially every multimedia format you will encounter in daily use.
Do I need to install anything to use FFmpeg Onlion?
No software installation is needed. FFmpeg Onlion is a pure web application — all you need is a modern browser that supports WebAssembly (Chrome, Edge, Firefox, or Safari). On first use, the browser downloads the ~31 MB FFmpeg WebAssembly core, which is then cached. Subsequent visits require no re-download, and the tool even works fully offline.
Will FFmpeg Onlion lag when processing large files?
Video processing in FFmpeg Onlion runs inside a Web Worker, so it never blocks the main thread — the UI remains responsive throughout. Processing speed depends on your device's CPU and memory; very large files (e.g. 4K video) will take longer. For everyday short-form video tasks like social media content, FFmpeg Onlion is typically fast enough.
What is the Operation Stack (chaining) feature in FFmpeg Onlion?
The Operation Stack is a key feature of FFmpeg Onlion. It lets you chain multiple operations (like crop, color grade, resize) into a single pass with one encode. This avoids the quality loss from repeated re-encoding and saves processing time. For example, you can do "crop + adjust + resize + format convert" all at once instead of step by step.
How does batch processing work in FFmpeg Onlion?
Click the "Batch" button in the input panel to switch to batch mode. You can then drag and drop or select multiple video files at once — they all go into a processing queue. Pick an operation, click "Process Video", and FFmpeg Onlion works through each file in sequence. Completed files can be downloaded individually or as a ZIP archive with preview support.
Is FFmpeg Onlion free?
Yes, FFmpeg Onlion is completely free. It is built on the open-source ffmpeg-webCLI project and licensed under GPL-3.0. You are free to use, modify, and distribute it. The source code is hosted on GitHub — community contributions and feedback are always welcome.
Ready to Process Your Videos with FFmpeg Onlion?
No sign-up. No uploads. Completely free. Open the page and go — your files never leave your device.