Compress video for Gmail (25 MB)

Gmail’s help page gives 25 MB as the largest attachment a personal account can send — read on 2026-09-24 and linked in the table above. Above it, Gmail puts a Google Drive link in place of the attachment. This page opens with 25 MB already chosen: drop a video and it is written again so that the file is at most 25 MB. A file already under it is told so and left alone.

The size decides the bitrate. 25 MB and the video’s length leave so many bits a second, and the picture is encoded to exactly that in two passes, aiming 3 % under so the file never comes out over; if it does, it is written again smaller before it is handed over. Sound that is already AAC or MP3 and fits in a tenth of the budget is copied as it is. When the bits are too few for the picture, a video of 50 or 60 frames a second plays at half its rate first, and only then is the picture made smaller — the button says which before you start.

Services change their limits, so the page links the help page and dates it rather than promising the number. The other sizes the compress page offers — 10, 20, 25, 50, 100, 200, 300 MB — are here too, for the other places you send to.

First the page asks the browser itself. Browsers carry the video encoders they use for calls and screen recording — H.264, VP9, AAC, Opus, often on the graphics chip — and when this browser can read your file and write the result with them, that is what happens: nothing is downloaded, the time is measured here first, and the line under the badge says the browser’s encoder did the work. MP4, MOV, WebM and MKV files usually qualify. AVI, WMV and FLV do not, and neither does an MP3, so those go the way below.

The work is done by FFmpeg, the program most video software is built on, compiled to WebAssembly so that it runs inside this page. It is large — 16.8 MB — and it is not downloaded until you press the button that says so. Then it reads your file, encodes 2 seconds from the middle of it as a test, and tells you how long the whole file will take on this device, before anything starts. That figure is measured here rather than taken from a table: the same engine and settings, your processor, your video. It is still an estimate, and it is labelled as one.

It is slower than a program installed on a computer. Here FFmpeg runs on one processor core, because a browser only lets a page use more when the site is served with particular security headers, and it cannot use the graphics chip’s video encoder at all. A long high-resolution video can take many minutes, and longer on a phone. The estimate says so before you commit to it, the progress line shows the time left as it goes, and Cancel stops it at once. When the browser’s own encoder can do the job, it is far quicker, and nothing is downloaded.