Your Video Is “Under the Limit” and Still Gets Rejected: How to Pick the Right Target Size

You check the file and it says 24 MB. The limit says 25 MB. The upload still fails. Or you run a compressor three times with different quality settings and get 31 MB, then 12 MB, then something that looks like it was filmed through a screen door.

Both problems have the same fix: decide the final size first, aim a little under the real ceiling, and let the encoder work backward from that number. Here is how I pick the number, and then a quick run on a real clip with VidSmaller (full disclosure: it's one of the tools I make).

The limit you see isn't the limit you get

The number a platform publishes is rarely the number your file has to beat.

• Email. Attachments travel base64-encoded, which makes them roughly 37% bigger on the wire. Gmail measures the encoded message, so a 25 MB video turns into a ~34 MB message. About 18 MB of actual file is what clears it. There's a longer explainer on why Gmail's 25 MB really means about 18. Outlook.com stops at 20 MB, and Exchange work accounts ship with a 10 MB default that many admins never change.
• Discord. The free tier went from 10 MB to 20 MB on 13 August 2026, but Discord's own help page still said 10 MB weeks later. If a file well under 20 MB gets refused, treat 10 MB as the fallback.
• WhatsApp. Video sent in a chat on mobile is capped at 16 MB.

These numbers move, so I check a dated table of upload limits by platform instead of trusting whatever a three-year-old forum post says. Here's what I actually type:

Where the video is going	Published limit	Target I use
Gmail / most personal email	25 MB	18 MB
Work email (Exchange default)	10 MB	about 7 MB
Discord, free account	20 MB (10 MB on older info)	19 MB, or 9 MB if refused
WhatsApp chat	16 MB	15 MB

Why a size target beats a quality slider

File size, length and bitrate are locked together. Divide the size by the duration and you have your bitrate budget, whether you like it or not. According to VidSmaller's bitrate calculator, 25 MB over one minute leaves about 3,300 kbps for the picture once a 128 kbps audio track is paid for.

A quality setting (CRF) holds the look steady and lets the size land wherever it lands. That's great for archiving and useless when there's a hard cap. A target-size encode flips it around: the size is fixed, and the encoder spends exactly that budget.

A real run: 13.9 MB clip, 10 MB target

I used a 12-second 1280×720 screen clip (13.9 MB) so the numbers are easy to follow.

Load the file

Open VidSmaller and drag the video onto the drop area. Without an account you get up to 500 MB per file, it takes MP4, MOV, MKV, WebM, AVI and about 30 other formats, and there's no watermark. The encode runs on VidSmaller's servers rather than your laptop. The trade-off is that the file gets uploaded. The upload is deleted when the job finishes, and the result is deleted when its download link expires.

Type the size you want

On the Basic Compression tab, type the number into Output file size. I entered 10, and the page showed "Estimated result: 10.0 MB" right away. If you'd rather not think about it, the chips under the slider fill in the usual targets: Discord 19, WhatsApp 15, Email 18, Reddit 100. This job cost one credit, and new visitors get some free without signing up.

Download, then check it

Hit Start Compression and wait for the cloud job. Mine came back as 13.9 MB → 9.3 MB (−32.8%), a little under the target rather than on it. That's the direction you want when the limit is strict. The download link stays live for two hours, so grab it and play it back once before you send it.

Still too big, or it looks rough?

• Drop the resolution before anything else. At a fixed size, fewer pixels each get more bits. Going from 4K to 1080p is usually the biggest single win, and a clean 720p beats a starved 1080p. Resolution lives on the Advanced Compression tab along with CRF and max bitrate.
• Only reach for H.265 if the other end can play it. It's roughly 30% smaller than H.264 on camera footage at the same quality, but it does worse on screen recordings, and older phones may refuse it. On VidSmaller it's part of the paid plans.
• Going to an old device? The old-device switch encodes with the baseline profile and yuv420p so the file plays almost anywhere.
• Long recordings cost more than one credit. A credit is one billed encoder minute, and a 1080p clip up to about seven minutes still fits in one. The pricing page breaks down what longer files cost.

When I wouldn't upload at all

For a short clip you'd rather keep private, an in-browser compressor like VideoCompress does the encode on your own device instead.