Compress video to a measured file size

A video compressor should measure the file it promises

A quality slider cannot answer a file-size limit. This compressor starts with the entered byte ceiling, reserves space for the MP4 container and AAC sound, then divides the remaining bits by the measured duration. That gives the H.264 encoder a defensible picture bitrate instead of a vague “medium quality” setting. The complete arithmetic stays visible before encoding begins.

Even that calculation is not proof. WebCodecs gives an encoder a target bitrate, not a contractual file size, and difficult motion may overshoot. CreatorValet therefore measures the written MP4. An oversized pass is discarded from scratch storage, its observed ratio lowers the next picture bitrate, and the browser tries again up to four times. The result says PASS only when the actual byte count is at or below the ceiling.

Compress video to 8 MB, 10 MB, 25 MB or your own ceiling

The presets are common transfer ceilings, not claims about a platform’s current subscription rules. Discord, email providers and workspaces can change limits or apply different limits by account. Confirm the number shown by the destination, enter it here, and use the measured receipt as the file-size answer. One MB on this page is exactly 1,000,000 bytes; the receipt prints both.

A tiny target cannot preserve arbitrary duration and resolution. The picture-budget warning uses the measured frame rate and selected output dimensions. If it says the squeeze is severe, shorten the source with the local video trimmer or choose a smaller long edge. Encoding anyway can satisfy bytes while destroying the reason to send the clip.

The MP4 created by this compressor

MP4

Full name	MPEG-4 Part 14
Extension	.mp4, .m4v
Format type	Video container — usually H.264 or H.265 with AAC
MIME type	video/mp4

What changes in the compressed MP4

The primary video becomes H.264 and the primary soundtrack becomes AAC. Both are lossy encodes. Aspect ratio is preserved, and the chosen long-edge limit never enlarges a smaller source. Descriptive container metadata, chapters, subtitles, alternate audio and extra video tracks are intentionally not copied. That makes the output boundary predictable and avoids carrying hidden fields into a file whose purpose is delivery.

“Lossless video compressor” is therefore not a promise made here. Lossless compression may reduce some sources, but it cannot guarantee a much smaller transfer ceiling. A byte target and unchanged encoded quality are competing constraints; this tool chooses the stated byte ceiling and reports the re-encode plainly.

Local processing still uses real device resources

Mediabunny reads MP4, MOV, WebM, MKV and other supported containers in byte ranges and drives the browser’s WebCodecs decoders and H.264/AAC encoders. Output streams to origin-private file storage when available, with an explicitly reported memory fallback. Long 4K clips can take minutes, heat the device and require enough free local storage for a pass. Canceling stops the active conversion; abandoned scratch files older than one day are removed on a later visit.

There is no URL import, cloud queue or invisible server fallback. A browser without the required source decoder or H.264/AAC encoder gets a capability explanation instead. You can inspect the local-processing boundary with the network verification guide. The media implementation uses Mediabunny over the browser’s WebCodecs APIs.