Practical tips
Sending a large file by email: real limits and good habits
File too large. That message often appears at the worst moment, just before a deadline. Yet it is easy to explain, and the solution is not always a file transfer service: quite often, a simple conversion to the right format, with the right setting, is enough to get the file through with no visible degradation. Here are the figures to know, and the standard method for each type of file.
The limits of the main email services
At the time of writing, Gmail and Yahoo Mail accept messages up to 25 MB, and Outlook.com attachments up to 20 MB. Corporate email systems are often stricter, with limits of 10 MB or even less, and the lowest limit between sender and recipient is the one that applies.
Above all, there is a trap few people know about: to travel inside an email, an attachment is encoded as text (so-called base64 encoding), which increases its size by about a third. A 20 MB file therefore takes up nearly 27 MB once encoded, and can be rejected by a stated 25 MB limit. In practice, aim for a file of at most 18 MB for a 25 MB limit, and 7 MB for a 10 MB limit.
Video: how much actually fits in an email
Video is almost always the file that gets stuck. To give concrete orders of magnitude, we converted an 89-second smartphone video, shot in 1080p at 60 frames per second, with FileXvert's reduction levels. The full details of this measurement are in our guide to reducing video size; here they are translated into sendable duration.
| Version | Size per minute | Duration for 18 MB |
|---|---|---|
| Original (MOV) | ≈ 177 MB | ≈ 6 s |
| MP4, balanced reduction | ≈ 52 MB | ≈ 21 s |
| MP4, smallest size (720p) | ≈ 11 MB | ≈ 1 min 35 s |
Bottom line: a short clip gets through with balanced reduction, but beyond about twenty seconds only the smallest size level, which brings the video down to 720p, keeps you under the limit. For a video several minutes long, no reasonable setting will do: a sharing link (Google Drive, OneDrive, iCloud, WeTransfer) is then the right solution.
Photos: the format matters more than the compression
A photo from a recent smartphone weighs 2 to 10 MB as JPG or HEIC, but a screenshot or a photographed document saved as PNG can exceed 25 MB on its own. In our measurements, a photo of a letter weighing 29.5 MB as PNG dropped to 4.7 MB as JPG, and to 1.1 MB as balanced WebP, with no visible difference on screen.
For several photos, the maths is simple: divide the practical limit by the number of images. Ten photos to send in an 18 MB message must weigh less than 1.8 MB each, which a balanced JPG easily achieves for an ordinary-sized photo.
Audio: MP3 solves almost everything
A WAV recording weighs about 10 MB per minute in CD-quality stereo. The same sound as a 128 kbps MP3 weighs less than 1 MB per minute: a voice memo or a twenty-minute interview then fits in a single email. For speech, the smallest size level (96 kbps) is enough and cuts the size by another quarter.
The method, file by file
Before sending, ask yourself what the recipient will do with the file: watch it on a phone, print it, edit it, archive it? The answer determines the setting.
- Video to watch: MP4, balanced reduction; smallest size if the video is longer than about twenty seconds.
- Video to edit or archive: do not compress, use a sharing link.
- Photo or photographed document: JPG, or WebP if the recipient can open it easily.
- Image for large-format printing: keep the best quality, and use a link if necessary.
- Audio: MP3 at 128 kbps for music, 96 kbps for speech.
- A Word document sent for reading: a PDF is lighter and looks the same everywhere.
Privacy: shrinking without multiplying copies
An email leaves copies: in the sent folder, with the recipient, in both mail providers' backups, and sometimes with people it gets forwarded to. So check the content, the recipients and the file name before sending, and prefer a time-limited link for sensitive documents.
Converting with FileXvert does not add an extra copy: the file is processed in your browser, without going through a conversion server. That is one transmission step fewer, which adds to your other precautions without replacing them.