Email attachment size limits, provider by provider

The limits

These are the published caps for the major providers. They have barely moved in fifteen years, which is the root of the problem: Gmail's 25MB limit was set in 2009, when a phone camera produced files a fraction of today's size.

Why your 24MB file still bounces

This catches people out constantly. Email cannot carry raw binary data, so attachments are re-encoded into text using a scheme called base64 before sending. That encoding makes the file roughly 33 percent larger in transit.

A 24MB video therefore arrives at the server as about 32MB and is rejected by a 25MB limit, even though the file on your disk was comfortably under it. The practical consequence is a simple rule: keep attachments under about 18MB for a 25MB limit, and under about 15MB for a 20MB one.

It gets worse in one particular case. If you attach several files, the encoding overhead applies to all of them together, so four 5MB photographs total roughly 27MB in transit rather than 20MB.

The limit that actually applies is the smaller of two

Both the sending and receiving servers enforce their own caps, and the message has to satisfy both. You can send a 24MB file from Gmail perfectly happily and still have it rejected because the recipient's employer caps incoming mail at 10MB.

This is why a message sometimes vanishes without an obvious error, or produces a bounce hours later. If someone tells you they never received an attachment you definitely sent, the recipient's limit is the usual explanation.

What to do about it

Compress the file

Usually the fastest fix, and often the only one needed. A phone photograph at 4MB routinely drops below 500KB with no visible difference on screen. A scanned PDF frequently halves. Our image compressor lets you specify the exact size you need, and the PDF compressor does the same for documents.

Bundle several files into one

When the problem is a dozen attachments rather than one large one, a single ZIP is easier for everyone. The ZIP tool can also split the result into parts that each fit under a limit you choose, so a 60MB folder becomes three separate 20MB emails that the recipient can open independently.

Use a link instead of an attachment

Gmail offers this automatically above 25MB, uploading to Google Drive and inserting a link. It works, but be aware the file then lives in cloud storage with whatever sharing permissions you set, which is worth a moment's thought for anything confidential.

Reduce the resolution before compressing

For video especially, dropping from 4K to 720p cuts the file dramatically while looking identical on a phone screen. Quality settings alone rarely rescue a large video; resolution is the lever that matters.

File types that are commonly blocked entirely

Separate from size, most providers refuse certain attachments regardless of how small they are, because they can carry malicious code. Executables such as .exe, .bat, .cmd, .msi and .jar are almost universally blocked, as are .js files.

Renaming the extension does not help, since providers inspect the file contents. Putting it inside a ZIP sometimes works and sometimes does not, as many scanners look inside archives too. For genuinely legitimate cases, a file-sharing link is the reliable route.

A rough guide to what fits

Assuming a 25MB limit and allowing for encoding overhead, roughly 18MB of actual file:

• Photographs — around 30 compressed images, or 4 or 5 straight from a modern phone.
• Scanned documents — a 50-page scan compressed, or about 10 pages uncompressed.
• Video — roughly 2 minutes at 720p, or 20 seconds straight off a phone at 4K.
• Audio — about 40 minutes at 64 kbps mono, or 2 minutes of uncompressed WAV.

Those figures explain why video is the format that causes the most trouble. Everything else usually compresses into range without much thought.