Video to MP4 - Online Video Format Converter — MP4 is the most widely compatible video format across devices, players, and platforms, built on the open ISO-BMFF container. This page encodes with the royalty-free VP8 codec (plus an optional VP8+Vorbis combination) while avoiding patented codecs. Supports format conversion, lossless remuxing, compression, scaling, looping, and resizing — all processed locally in your browser, with files never uploaded to a server. A built-in metadata / tag editor reads the source video's tags (title, artist, album, album artist, date, genre, track, comment), lets you edit them, and writes them into the output — including the no-re-encode copy mode, where quality is perfectly preserved.
Supported input: Videos using open royalty-free codecs such as VP8/VP9/AV1/MPEG-4/FFV1 (WebM, MKV, MP4, MOV, AVI containers). Everything is converted locally in your browser; files are never uploaded to a server.
First use loads an ~30MB video processing engine into the current browser. It is cached and reused afterwards, so please be patient.
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Click to select or drag and drop a video file
Supports WebM, MKV, MP4, MOV, AVI and other common formats; under 500MB recommended
Quality:60higher = better quality, larger file
Target bitrate:kbps; leave empty to decide automatically from the quality slider
Resolution:scaled automatically to preserve the original aspect ratio, no stretching
Loop count:the output video will play N times consecutively
Percent:100%scaled as a percentage of the original size
W×H:×fill in either value to scale proportionally; leave empty to use percent
Format Convert: Pick a codec combination and click the button below to remux/re-encode the video as MP4. If the input codec is MP4-compatible, choose "No re-encode" for instant remuxing (no quality loss).
Video Compress: Re-encodes the video to MP4 with the chosen quality or target bitrate to produce a smaller file. This mode requires re-encoding, so "No re-encode" is unavailable.
Video Scale: Scales the video to a preset resolution and outputs MP4. This mode requires re-encoding, so "No re-encode" is unavailable.
Video Loop: Repeats the video content N times and outputs MP4. Combined with "No re-encode" this completes almost instantly.
Video Resize: Scales the video by percentage or explicit width/height pixels and outputs MP4. This mode requires re-encoding, so "No re-encode" is unavailable.
Rewrites the metadata with a stream copy — video and audio are not re-encoded, so quality is perfectly preserved.
What is MP4? Container vs codec
MP4 is not a way of compressing video — it is a box. Formally it is the ISO Base Media File Format (ISO-BMFF): a structured container that holds one or more already-compressed streams (a video track, an audio track, maybe subtitles) plus metadata, all organized as nested boxes that a player walks through like a table of contents. What actually squeezes the pixels is the codec stored inside — most commonly H.264 (also called AVC) or the newer HEVC (H.265), and on this site the royalty-free VP8/VP9 family. "Container vs codec" is the single most useful distinction in video files: an MP4, MKV, MOV and WebM can all hold the very same H.264 stream, which is why moving a video between containers (remuxing) takes seconds and loses nothing, while changing codecs (re-encoding) rewrites every frame.
Five facts to anchor the rest of the page:
• MP4 = container (ISO-BMFF boxes: ftyp, moov, mdat); the codec (H.264, HEVC, VP8/VP9) is the compression method stored inside
• same stream, different box: remuxing MP4↔MKV↔MOV copies bytes, re-encoding rewrites frames
• moov = the index box; its position decides whether the file can start playing before it finishes downloading
• 1080p = 1920×1080 = 2,073,600 pixels; 4K UHD = 3840×2160 = exactly 4× more pixels to encode every frame
• bitrate arithmetic: 8 Mbps = 1 MB per second → a 1-hour video at 8 Mbps is about 3.6 GB
The moov atom and why some MP4s refuse to stream
The moov box is the file's master index: frame positions, timing, track list. Encoders normally write it at the end of the file, because only when encoding finishes do they know where every frame landed. A player cannot start without the index, so a web player must download the whole file first — which is why some MP4s will not play until fully downloaded. Moving the moov box to the front (the "faststart" layout) fixes streaming: the player grabs the index first, then fetches frames on demand. Converting with a faststart-style layout changes only the box order, never the compressed frames.
Remux vs re-encode
Remuxing ("no re-encode" on this page) copies the compressed video stream into a new container untouched — byte-for-byte identical frames, finished in seconds, zero quality loss. It works whenever the stream is already compatible with the target container. Re-encoding decodes every frame and compresses it again; it is unavoidable when you change codecs, scale the picture, or apply filters, and each pass re-quantizes the image, so a little quality is spent. A practical rule: change container or metadata → remux; change anything about the pixels → re-encode.
H.264, HEVC and the royalty-free choice
H.264/AVC (finalized 2003) is the most universally playable video codec in existence and the safe default of the whole industry. HEVC/H.265 (2013) roughly halves the bitrate H.264 needs for the same visual quality, at the cost of heavier encoding and a messier patent-licensing situation. The VP8/VP9 family and AV1 are the royalty-free alternatives developed to escape those license fees; VP9 typically lands between H.264 and HEVC in efficiency. This page writes VP8 into MP4 precisely because the codec, not the container, is what carries patent obligations — MP4 itself is an open ISO standard and legally holds any stream a player will accept.
Common misconceptions
"MP4 is a codec." It is a container. Two MP4 files can contain completely different codecs, which is why one plays on your TV and the other does not — the player rejected the stream, not the file.
"Converting always loses quality." Only re-encoding does. Remuxing the same stream into MP4 is lossless and near-instant; this page's "No re-encode" mode does exactly that.
"A bigger file must be better quality." File size = bitrate × duration. An inefficient old codec at double the bitrate often looks worse than a modern codec at half of it — compare codecs at similar visual quality, not similar size.
"MP4 files that won't stream are broken." Usually the moov box simply sits at the end of the file; a faststart re-layout makes the identical video streamable.
Related tools: Video to MKV for the fully open Matroska container, Video to WebM for the royalty-free WebM pairing, Video Cutter for keyframe-accurate trimming without re-encoding, and Add/Extract Subtitles to embed text tracks into MP4.
