What is Video Bitrate Adjuster?

Re-encode any video at a different bitrate to trade file size for visual quality. Lower the bitrate to shrink large recordings for sharing, or raise it to keep detail for archival. Save as MP4 for universal playback or MOV for Apple workflows — both encoded with H.264. It runs on ffmpeg.wasm, so your files never leave your device.

The encoder runs inside ffmpeg.wasm, so the whole job stays on your device. Choose how to drive the encode: set an average bitrate (100 kbps to 20 Mbps), type a target file size and let the tool work out the bitrate from the clip length, or use the CRF slider for constant visual quality whatever the motion. A delivery target (WhatsApp, Email, Mobile, Web, Archive) fills in a sensible bitrate and resolution in one click, and a separate audio-bitrate control lets you shrink speech further or keep music crisp. Save as MP4 for universal playback or MOV for Apple workflows, both encoded with H.264, then compare the original and the new clip side by side before downloading.

How to use

1. Upload your video file (MP4, WebM, MOV, or AVI up to 2 GB).
2. Choose a mode — Bitrate, Target Size, or Quality (CRF) — and set the value, or tap a delivery target (WhatsApp, Email, Mobile, Web, Archive) for instant settings. Optionally drop the resolution to 1080p, 720p, 480p, 360p, or 240p and pick an audio bitrate for an extra size cut.
3. Click Re-encode, preview the result, then download the adjusted video.

When to use

• Shrinking a screen recording or webinar so it fits an email attachment limit.
• Re-encoding phone footage at a lower bitrate before uploading to Slack or WhatsApp.
• Cutting the bitrate of an over-sized 4K clip down to a sane streaming target.

Result

You recorded a 45-minute lecture at 8 Mbps (2.7 GB). Set the target to 2 Mbps — the file shrinks to ~675 MB while keeping the slides perfectly readable.

FAQ

What bitrate should I pick for a given resolution?

Rough guidance for H.264: 720p sits well around 2.5 to 4 Mbps, 1080p around 4 to 8 Mbps, 1440p around 9 to 16 Mbps, and 4K around 35 to 45 Mbps for smooth motion. Talking-head and screencast content can go lower than action footage.

Will lowering the bitrate make my video blurry?

It softens detail rather than blurring the whole frame. The first artefacts you usually see are blockiness in dark areas, smeared fast motion, and washed-out gradients. Static scenes hold up much better than panning shots at the same bitrate.

Should I save as MP4 or MOV?

MP4 is the safe default and plays on practically anything — phones, browsers, TVs, and editing apps. Pick MOV when you are handing the clip to Apple software like Final Cut or QuickTime. Both export the same H.264 video at your chosen bitrate, so the picture quality and file size are identical; only the container wrapper differs.

Can I raise the bitrate above the original to improve quality?

No, encoding higher than the source only inflates file size. Detail discarded by the original encoder cannot be recovered. Use a higher bitrate only when the source itself is already high quality and you want minimal loss on re-encode.

How long does the re-encode take?

Because ffmpeg.wasm runs locally on your device, expect roughly real-time on a recent laptop, slower on phones, and slower again for 4K. A ten-minute 1080p clip typically finishes in five to fifteen minutes depending on the machine.

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