Video too large to email? How to get under the attachment limit
Personal Gmail caps attachments at 25 MB and quietly swaps anything larger for a Google Drive link. Outlook.com refuses attachments over 20 MB from your device and offers a OneDrive link instead. Work accounts on Google Workspace or Microsoft 365 use whatever ceiling the administrator set, which can be lower.
Before you compress anything blindly, find out why the file is huge. It is almost always a 4K clip from a phone. Dropping it to 1080p and letting a constant-quality encode do the rest gets you under the cap with far less visible damage than a generic squeeze.
Why a short clip weighs so much
A video file's size is almost entirely its bitrate multiplied by its duration. The arithmetic is simple enough to do in your head: megabytes ≈ bitrate in Mb/s × seconds ÷ 8. A one-minute clip at 8 Mb/s is roughly 60 MB. The same minute at 2.5 Mb/s is roughly 19 MB.
Phone cameras record at bitrates designed for archiving, not for sending. A modern iPhone or Android handset shooting 4K at 60 fps writes somewhere in the tens of megabits per second, so a fifteen-second clip can clear the 25 MB line on its own. Screen recordings behave the same way, because a full-resolution desktop capture of a moving window is expensive to encode even when very little is happening on screen.
Two things follow. First, resolution is the biggest lever you have — a 1080p frame is a quarter of the pixels of a 4K one, and needs far fewer bits to look about as sharp in an email window. Second, length matters just as much as quality. If the useful part of your clip is twenty seconds inside a three-minute recording, trimming it beats any compression setting. Our in-browser converter deliberately does not trim — it converts and re-encodes, nothing else — so do the trimming in your phone's Photos app or your operating system's built-in player first, then bring the shorter clip here.
What the limits actually are
| Mailbox | Attachment ceiling | What happens above it |
|---|---|---|
| Personal Gmail | 25 MB per message | The attachment is removed and replaced with a Google Drive link |
| Google Workspace (work or school) | Set by your administrator | Same Drive-link substitution, at whatever ceiling was configured |
| Outlook.com | 20 MB per message | Outlook offers to upload to OneDrive and send a link instead |
| Microsoft 365 work account | Set by your administrator | The message is rejected or converted to a OneDrive link |
| Any recipient | Their server's inbound limit | A bounce message, often hours later |
The recipient's limit is the one people forget. Your outbound cap can be generous and the message will still bounce if their mail server refuses anything over, say, 10 MB. When you do not know where the message is going, treat 20 MB as the practical ceiling rather than 25 MB.
Encoding overhead is real. Mail servers wrap binary attachments in base64 text, which adds roughly a third to the size on the wire. A 25 MB message limit can therefore mean a file closer to 18–19 MB in practice. Aim comfortably under the number rather than exactly at it.
Step one: look at what is actually in the file
Compressing without looking is how people end up with a soft, blocky video that is still too big. Drop the clip onto the converter and read the panel it shows before you press anything: container, video codec and profile, resolution corrected for rotation, frame rate, duration, audio codec, file size and overall bitrate. That is the whole diagnosis.
Three readings tell you what to do:
- 3840×2160 at 30 or 60 fps. Set resolution to 1080p and you are usually most of the way there without touching quality at all.
- An overall bitrate far above what the picture needs — a mostly static screen recording at 20 Mb/s, for example. A re-encode at constant quality will collapse it dramatically.
- A long duration. If it is eight minutes of 1080p, no setting will make it a sensible attachment. Skip to the link section below.
If you would rather read the file's details on their own before deciding anything, the guide on checking a video's codec in your browser covers the same panel and what each field means.
Getting under the cap, in order of what to try
- Drop the resolution. 4K to 1080p is the single most effective change, and for something that will be watched in an email window it costs you nothing perceptible. 720p is fine for a screen recording or a clip of a whiteboard.
- Lower the frame rate — but only if the source is 60 fps and the content is not fast motion. 60 to 30 fps roughly halves the number of frames to encode. Do not do this to footage of sport or anything panning quickly.
- Re-encode at the Medium quality preset. The default presets are constant-quality (CRF), which means the encoder spends bits where the picture needs them and skips the rest, so the file ends up only as large as the clip genuinely requires.
- Remove or shrink the audio. Setting audio to "remove" saves a couple of megabytes on a long clip. For a silent screen recording it is free.
When you need to hit a specific number
Constant quality is the better default, but it will not let you predict the exact size in advance. When you need a hard target, switch the advanced rate-control option from CRF to the fixed bitrates — 1, 2.5 or 5 Mb/s — and use the arithmetic above. At 1 Mb/s, roughly two and a half minutes of video fits inside 20 MB. At 2.5 Mb/s, roughly a minute does. Add a megabyte or so for audio and leave headroom for the encoding overhead.
A re-encode is not lossless, whatever the quality setting says. You are throwing away picture data to make the file smaller — that is the whole point here. Keep the original. If you ever need a size reduction that costs nothing, you are looking for a container change instead, which is what the guide on converting MOV to MP4 without losing quality describes.
Make sure it plays when it arrives
Getting under the limit is only half the job. A clip recorded by a recent iPhone is likely to be HEVC inside a MOV, and both halves of that can fail at the other end: MOV confuses Windows file associations, and HEVC needs a decoder that older Windows installs do not have. You compress it successfully, it sails through the mail server, and the recipient double-clicks it and sees an error.
The safe combination for something you are emailing to a person whose setup you do not know is H.264 video and AAC audio inside an MP4. That plays on Windows, macOS, Android, iOS, every browser and almost every TV. If your file is already HEVC, convert it with HEVC to H.264 rather than only shrinking it, and read why HEVC video refuses to play on Windows 11 if you want the reason. The related problem of a MOV file not playing on Windows is a container issue with the same fix.
When a link is genuinely the right answer
Some videos should not be attachments. Anything over a few minutes at a resolution worth watching will not fit inside 20 MB without looking bad, and the honest move is a Drive, OneDrive or WeTransfer link — or a different channel altogether. If the recipient is on the same messaging platform, sending it there is easier: the caps and the compression behaviour are different, and we cover them in the guides on converting video for WhatsApp and sending a large video on Discord without Nitro.
The one case where an attachment is worth fighting for is a work file that must arrive as a file — a signed record, evidence, something going into a case management system that cannot follow a link. That is also the case where uploading the video to a random conversion website is a policy problem rather than a preference. The converter on this site runs FFmpeg compiled to WebAssembly inside your own browser tab, so the file never leaves the machine; if that distinction matters to you, whether online video converters are safe goes through what "online converter" normally means architecturally.
Doing it on the phone the video came from
If the clip is sitting in your camera roll and you never want it on a computer, the browser converter will run in a phone browser, but a 4K source is heavy going: the WebAssembly build is single-threaded, and a re-encode of 1080p footage runs slower than real time. Files over 2 GB are refused outright, and over about 300 MB the page warns you, because converting needs roughly three times the file size in free memory.
The Video Converter app for iPhone and its Android counterpart use the phone's hardware encoder instead, which is far faster on long or 4K footage and has no size ceiling. The trade-off is control: the app always re-encodes, offers Low, Medium and High as fixed bitrates of 1, 2.5 and 5 Mb/s, and has no resolution or frame-rate setting. For an email attachment that is usually enough — Low on a short clip lands well inside the cap. On Android the app is free and unlimited; on iPhone the first conversion is free and further conversions need the paid upgrade.
Convert it right now
The converter on this site is free and unlimited, and your file is never uploaded - it is read from your disk into this tab and converted there.