Compress a video to under 100KB (the toughest size target)

It happens more often than you'd think: a video that needs to be under 100KB.

100KB is about a one-page Word document or a phone snapshot at low resolution. It's tighter than the average phone snapshot and a long way from a raw scanner output. Getting there cleanly is doable, but the defaults most software ships with are tuned for archival quality, not for hitting a hard upload limit.

Run it in your browser: WebM to MP4 — No upload, no signup, no daily limit.

What 100KB actually looks like

For context — 100KB of a video is roughly about a one-page Word document or a phone snapshot at low resolution. If the original video is dramatically larger, expect a visible quality drop. If it's only marginally over, you'll hit 100KB without compromising the look.

How to hit the 100KB target with WebM to MP4

Open WebM to MP4. No install, no signup.
Drop the video on the upload area. WebM to MP4 reads it locally — the file never goes to a server.
Choose the most aggressive preset available. For tight size targets, you want maximum compression. The middle setting won't get you to 100KB on the first pass.
Check the output size badge. WebM to MP4 shows the result size next to the download button. If it's still above 100KB, run it through a second time with the aggressive preset.
If you need exactly 100KB, accept slightly more aggressive compression than feels comfortable. Most viewers will not notice; the upload portal will.

When the first pass isn't enough

Some videos fight back. Three reliable second-pass tricks:

Downsize first, then compress. If the video has more resolution than the final use needs, reduce dimensions before re-encoding. Half the pixels = a third the file size, with no visible loss for screen viewing.
Strip embedded metadata. EXIF, color profiles, thumbnails, and history layers can add 10–30% to the size with zero visual impact. WebM to MP4 strips them automatically on aggressive presets.
Convert format on the way down. If the video is in a lossless format, switching to a lossy one (where appropriate) often beats any in-format compression. WebM to MP4 suggests the right output format based on what you're optimising for.

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Runs entirely on your device using open web standards.

Why 100KB is such a common target

It's not a coincidence. Most upload forms — government portals, university applications, job-board file uploads — settled on 100KB or thereabouts because it's the largest size that still loads quickly on mobile networks worldwide. Knowing how to hit 100KB reliably solves about 60% of all "my file is too big" situations.

Frequently asked questions

Does WebM to MP4 support batches?

Yes — drop multiple videos at once and they all hit the 100KB target. Useful when a portal asks for multiple documents within the same per-file cap.

Will WebM to MP4 change the file extension?

Only if you ask it to. By default it keeps the original extension and only changes the bytes inside. The output drops in cleanly anywhere the original would have.

What if I need a video under 100KB but it must look perfect?

Lossless compression can only do so much. If you absolutely cannot lose visual quality, the answer is reducing the content — fewer pages, lower resolution where lower resolution would have been fine to begin with. WebM to MP4 can help with both.

What's the smallest a video can reasonably get?

It depends on content. A pure-text video can compress to a few KB. A photo-heavy video hits diminishing returns somewhere between 50KB and 200KB depending on the image content.

Related guides

Ready to try it?

Use the tool: WebM to MP4. Browser-only. Nothing is sent to a server.

Last reviewed May 2026. File-size limits, portal requirements, and software defaults change over time — always verify with the destination platform before uploading time-sensitive documents. References to third-party services and products are for descriptive purposes only and do not imply any partnership or endorsement.