How to "attachment too large" — fix an oversized video in one pass
- Step 1Drop the file that got rejected — Drag the oversized clip onto the tool —
MP4,MOV,MKV,WebM,AVI,M4V, orTS. A fast<video>probe reads the duration so the bitrate budget is right; no engine load yet, so this is instant. - Step 2Pick the target that matches the error — If Gmail bounced it, leave the
Targeton GMAIL (24 MB). If Outlook rejected it, switch to OUTLOOK (19 MB). When in doubt — or if the bounce came from a corporate relay — pick OUTLOOK; the smaller target clears more gateways. - Step 3Run it — Click Run Email Fit. JAD solves
totalKbps = target x 8 / duration, reserves 128 kbps for audio (96 kbps under 30 s), and gives the rest to video. The dashboard shows whether it's on the fast hardware path or the FFmpeg.wasm fallback. - Step 4Download the result — The card shows the before → after size — e.g. 58 MB → 23 MB. Download the MP4.
- Step 5Re-attach and send — Drop the new file into compose. Now under the cap, it attaches inline and the 'too large' wall is gone — no Drive/OneDrive prompt.
- Step 6Still bouncing? Go smaller or shorter — If a corporate relay still rejects it, the cap is below 19 MB or it's counting the Base64-inflated size. Trim the clip with the lossless trimmer and re-run — fewer seconds means a smaller file at the same quality.
Which target fixes which error
Match the 'too large' message to the target. There is no custom MB field — these two presets are the entire control surface.
| Where the error came from | Cap | Target to pick | JAD output size |
|---|---|---|---|
| Gmail (web or app) | 25 MB | GMAIL | ~24 MB MP4 |
| Outlook.com | 20 MB | OUTLOOK | ~19 MB MP4 |
| Corporate Exchange relay | Often 10 MB | OUTLOOK + trim first | < 19 MB after trimming |
| Unsure / generic 'too large' | Varies | OUTLOOK (safer) | ~19 MB MP4 |
Typical before → after for the quick fix
Representative results. Exact output varies with source complexity, but the target keeps it under the cap.
| Source | Duration | Target | Result |
|---|---|---|---|
| iPhone 4K .mov (HEVC) | 30 s | GMAIL | ~140 MB → ~23 MB, H.264, previews |
| OBS screen capture .mp4 | 90 s | GMAIL | ~70 MB → ~23 MB |
| Zoom recording .mp4 | 2 min | OUTLOOK | ~95 MB → ~18 MB |
| GoPro .mp4 (1080p) | 45 s | GMAIL | ~60 MB → ~23 MB |
Cookbook
The exact 'too large' situations people hit, and the one-pass fix for each. All sizes approximate.
Gmail rejected a 4K iPhone clip
A 30-second 4K .mov was ~140 MB and HEVC — both too big and not previewable. One pass on GMAIL fixes both at once.
Error: Gmail offered a Drive link (file too large) Input: IMG_5102.mov · 140 MB · 30 s · 4K HEVC Target: GMAIL Output: img-5102.mp4 · ~23 MB · H.264 Result: attaches inline AND previews in Gmail
Outlook desktop refused to send
Outlook.com bounced a 2-minute Zoom recording at 95 MB. The OUTLOOK target brings it under 20 MB.
Error: 'The attachment size exceeds the allowable limit' Input: zoom-recording.mp4 · 95 MB · 2 min Target: OUTLOOK (19 MB) Output: zoom-recording.mp4 · ~18 MB Result: sends from Outlook without the OneDrive prompt
Corporate relay still bounces at 19 MB
An on-prem Exchange relay capped messages at 10 MB. Compression alone can't clear it — trim, then compress.
OUTLOOK preset -> ~19 MB -> still bounced (10 MB cap) Fix in two steps: 1. lossless-trimmer -> keep 40 s of the 3 min clip 2. email-compressor (OUTLOOK) -> ~7 MB Result: under the 10 MB corporate limit
No-install fix on a locked-down work laptop
IT blocks new software, so HandBrake isn't an option. The browser tool needs no install and no admin rights.
Constraint: cannot install desktop apps Action: open JAD in the browser, drop clip, pick target, run Path: WebCodecs HW H.264 (or FFmpeg.wasm fallback) Result: ~23 MB MP4, nothing uploaded, no install
Quick check: is it already under the cap?
Sometimes the file is barely over. The result card's before→after tells you instantly whether you even needed to compress.
Input: clip.mp4 · 26 MB · Gmail rejected (over 25) Target: GMAIL Output: clip.mp4 · ~23 MB Result: 3 MB under the cap — attaches fine now
Edge cases and what actually happens
File still 'too large' after compressing
Cap below targetIf it still bounces, the receiving cap is below the target you picked (e.g. a 10 MB corporate limit vs the 19 MB OUTLOOK target), or the relay measures the Base64-inflated size. Trim the clip with the lossless trimmer and re-run — fewer seconds means a smaller file.
Output edged slightly over the target
Soft overshootThe encoder solves for a bitrate; it doesn't iterate to a guaranteed byte count. A short, busy clip can land a hair above the target. It still gives you the file (with a console warning). If it's over the cap, switch to the smaller OUTLOOK target or trim a couple of seconds.
Source won't load / 'no video files in the drop'
Invalid inputOnly MP4, MOV, MKV, WebM, AVI, M4V, and TS are accepted. A .gif, image, or audio file is rejected with a clear message. If your clip is in an odd container, rewrap it to MP4 with the transcoder first.
'Could not determine video duration'
RejectedA truncated download or broken container can leave the duration unreadable; the tool refuses to guess a bitrate and throws this error. Re-export the source or rewrap it cleanly, then retry.
Trying it on a phone with a big file
Mobile capOn mobile without hardware encode, the FFmpeg.wasm fallback won't take sources over 80 MB and tells you to trim or use desktop. Above 720p it auto-downscales to 720p to avoid running the phone out of memory mid-encode.
Very long clip comes out blocky
Quality limitThe quick fix sizes for the cap, not for quality. A 10-minute clip squeezed into 24 MB hits the 200 kbps video floor and looks rough. For long footage, trim to what matters or send a link — no compressor can put 10 minutes of detail in 24 MB.
You picked GMAIL but the error was from Outlook
Wrong targetGMAIL targets 24 MB, which is still over Outlook's 20 MB cap. If Outlook rejected it, switch to OUTLOOK (19 MB) and re-run. When unsure which client will receive it, OUTLOOK is the safer choice.
Already-small file run anyway
Still worksRunning a file that's already under the cap is harmless — it just re-encodes toward the target and may come out smaller. If it already attaches fine, you don't need to compress at all.
Frequently asked questions
Why does my email say the video attachment is too large?
Your file exceeds the mailbox cap — 25 MB for Gmail, 20 MB for Outlook.com, and often lower on corporate Exchange. The fix is to shrink the file below the cap before sending, which this tool does in one pass.
How fast is the fix?
Drop, pick a target, run, download. On the WebCodecs hardware path a short clip finishes in seconds; the FFmpeg.wasm fallback is slower but still a single pass with no upload wait.
Do I need to install anything?
No. It runs in the browser — no HandBrake, no FFmpeg install, no admin rights. That's the point for locked-down work machines.
Is my video uploaded anywhere?
No. The encode happens entirely in your browser via WebCodecs or FFmpeg.wasm. The file never leaves your device.
Which target should I pick?
Match it to the error: GMAIL (24 MB) if Gmail bounced it, OUTLOOK (19 MB) if Outlook did. If you're unsure or it's a corporate relay, pick OUTLOOK — the smaller target clears more gateways.
Can I just type the exact MB I need?
No — the only options are GMAIL (24 MB) and OUTLOOK (19 MB). To hit a smaller size, trim the clip first so the same target yields fewer megabytes, or use whatsapp-compressor (15 MB).
It's still too large after compressing — what now?
The receiving cap is below the target (e.g. a 10 MB corporate limit), or the relay counts the Base64-inflated envelope. Trim the clip to fewer seconds with the lossless trimmer and re-run.
What format does the fixed file come out as?
An H.264 + AAC MP4 — universally email-friendly. It also fixes HEVC iPhone clips that wouldn't preview, since the output is always H.264.
Will the quality be ruined?
For short clips, no — they keep a high bitrate at the cap. Quality only suffers on long clips because the same target bitrate has to stretch across more time. Trim long footage for the best result.
What's the biggest file I can fix?
On the free tier, sources up to 1 GB (one file). The only hard reject is on mobile without hardware encode, where the FFmpeg.wasm fallback won't take sources over 80 MB.
What if the file won't even open in the tool?
Only MP4, MOV, MKV, WebM, AVI, M4V, and TS are accepted. For an unusual container, rewrap it to MP4 with the transcoder first, then compress.
Can I do this repeatedly without re-uploading each time?
Yes — pair the @jadapps/runner once and POST to http://127.0.0.1:9789/v1/tools/email-compressor/run with options matching GET /api/v1/tools/email-compressor. Everything still runs locally.
Privacy first
Every JAD Video tool runs entirely in your browser via WebCodecs and FFmpeg (WebAssembly). Your video files never leave your device — verified by zero outbound network requests during processing.