Compress image for email
Email caps you at 25MB. Drop an image in and it comes back underneath that ceiling, at the best quality that fits.
The limit you actually have to beat
Gmail caps attachments at 25MB and Outlook at 20MB, but those are limits on the whole message after encoding, not on one file. Base64 encoding adds roughly a third, so a 20MB image can push a message over a 25MB ceiling on its own.
Keep individual images under 5MB when emailing several at once, and well under 1MB if the recipient may be reading on a metered mobile connection.
Why compress image for email at all
Because the 25MB ceiling is enforced, not advisory. An upload that exceeds it fails outright, usually without telling you which file was the problem. Working backwards from the number — rather than nudging a quality slider and re-testing — is the difference between one pass and five.
Picking a target below 25MB
Aim a little under the stated ceiling rather than exactly at it. Limits are usually enforced on the encoded upload rather than on the file as it sits on your disk, and a few percent of overhead is common. Setting a target around ninety percent of the published number costs you almost nothing visually and avoids a rejected upload.
The other habit worth forming is to compress image for email from the original rather than from something you already shrank. Every lossy re-encode compounds, and an image that has been through three rounds of "make it smaller" looks markedly worse than one that went from camera output to its final size in a single pass — even when both end up at the same number of bytes.
How the target is reached
Most compressors give you a quality slider and let you find out afterwards how big the file turned out. That is the wrong way round when you have a hard ceiling. This tool works backwards from the number: you ask it to compress image for email, and it searches for the encoder setting that lands just underneath.
The search is a binary search over the JPEG or WebP quality parameter. It encodes at the midpoint of the remaining range, checks the byte count against 25MB, and moves the range accordingly. Nine passes narrow the setting far finer than the eye can resolve, and every pass keeps the best result that fit — so what comes back is the highest quality version that still fits, not the first one that happened to work. Nine passes is also fast enough that you can compress image for email, look at the result, change the number and run it again without ever waiting on a progress bar.
When quality alone cannot get there, the tool reduces pixel dimensions in steps and searches again. That order matters: dropping quality first preserves your framing, while shrinking first throws away detail no quality setting can recover. Final dimensions are listed next to the file whenever a resize was needed, so an attempt to compress image for email never quietly returns something smaller than you asked for without saying what it gave up to get there.
Nothing is uploaded
Nothing you drop onto this page leaves your device. The image is decoded, re-encoded and handed back entirely inside the browser tab. There is no upload, no queue, and no temporary copy sitting on someone else's disk waiting for a retention policy to delete it.
That matters more than it sounds. The files people most often need to shrink are the ones they should be most careful with: passport scans, signatures, identity documents, medical forms. Handing those to an unknown server in exchange for a smaller file is a poor trade. Because the work is local, you can compress image for email with the network disconnected and get the same result.
It also means there is no queue to wait in and no daily allowance to run out of. Server-side compressors have to ration free use because every file costs them CPU time; here the CPU is yours, so you can compress image for email as many times as you like, on as many files as you like, without an account.