Why email rejects your photo
Every email provider sets a hard maximum size on attachments. If your file is bigger than the limit, the email simply refuses to send — usually with an error like "Attachment too large" or "Message size exceeds maximum permitted". The exact threshold depends on the provider:
| Email provider | Attachment limit | Safe target size |
|---|---|---|
| Gmail | 25 MB | ≤ 18 MB |
| Outlook / Microsoft 365 | 20 MB | ≤ 15 MB |
| iCloud Mail | 20 MB | ≤ 15 MB |
| Yahoo Mail | 25 MB | ≤ 18 MB |
| ProtonMail | 25 MB | ≤ 18 MB |
| Most corporate servers | 10–15 MB | ≤ 8 MB |
Notice the "safe target" is always smaller than the stated limit. That's because email attachments are MIME-encoded for transit, which inflates them by about 33%. A 25 MB file becomes roughly 33 MB on the wire — and many servers along the route enforce their own stricter limits. Compressing to the safe target guarantees the message gets through.
What "compression" actually does
Modern phones and cameras save photos at very high quality — typically 4–12 MB per photo, sometimes more. That's great for archiving and printing, but overkill for screen viewing. JPEG compression reduces the file size by storing the same image with slightly less precision in the colour values. At 75% quality, the file is typically 5–10× smaller, and almost nobody can tell the difference on a screen.
This is the same technique Apple and Google use when they "optimize" the photos you upload to iCloud or Google Photos. You're not losing the picture — you're losing the parts of it that human eyes can't see anyway.
Step by step
- Open the compressor at unfuss.app. The page loads, then runs entirely on your device. Nothing is uploaded.
- Drop your photo (or multiple photos) onto the drop zone. JPG, PNG, and WebP files are all supported. HEIC files from iPhone need to be converted first — use unfuss.app/heic-to-jpg.
- Leave the quality slider at 75%. That's the sweet spot for email attachments — fast compression, no visible quality loss.
- Watch the output. Each photo's new file size is shown. A typical 8 MB iPhone photo will compress to 1–2 MB.
- Download the compressed file (or all of them as a ZIP) and attach to your email. Done.
Sending multiple photos
If you're emailing a folder of vacation photos, compress them all in one batch instead of one at a time. The
compressor takes any number of files at once, runs them in parallel, and lets you download the whole set as a single
.zip archive. Your recipient then unzips on their end. This is much faster than attaching twenty
individual files and almost always slimmer than the raw originals.
If even the compressed batch is over your provider's limit, switch to a file-sharing link instead — Google Drive, Dropbox, or WeTransfer all give you a shareable URL for any size of upload, which you paste into the email body instead of attaching the file.
Frequently asked
What is the maximum email attachment size?
Gmail and Yahoo cap at 25 MB per email. Outlook and iCloud Mail cap at 20 MB. Many corporate email servers enforce even lower limits — 5 to 15 MB. If your provider rejects an attachment, the file is over the limit. Compress and try again.
Why does my email say "too large" when the file is under the limit?
Email attachments are MIME-encoded for transit, which inflates them by about 33%. A 25 MB file becomes roughly 33 MB on the wire. Combine that with stricter limits on intermediate mail servers and you can hit "too large" well before the stated cap. Always compress to a safe target — 18 MB or less for Gmail, 15 MB or less for Outlook.
Will compression hurt my photo's quality?
At 75% quality, the file shrinks dramatically with no quality loss visible on a screen. For photos meant for large prints, stay at 90% or higher. For email — which the recipient will view on a screen — 75% is the right balance.
Can I compress multiple photos at once?
Yes. Drop all of them onto the compressor at the same time. Each photo is processed in parallel and you can download them individually or as a single ZIP. This is much faster than compressing one at a time.
Is the photo uploaded anywhere?
No. The compressor runs entirely in your browser using JavaScript. Your photo never leaves your device. You can verify this by opening your browser's developer tools, switching to the Network tab, and dropping a photo — no upload requests appear.
What's the best file format for email photos?
JPEG (.jpg) is the universal standard. It compresses photographs efficiently and every email client and operating system can open it. If you have HEIC files from an iPhone, convert them to JPEG first at unfuss.app/heic-to-jpg — otherwise the recipient may not be able to open them.
What if the file is still too large after compressing?
Switch to a file-sharing link instead of an attachment. Upload to Google Drive, Dropbox, OneDrive, or WeTransfer (free, no account needed) and paste the share link into your email. The recipient clicks it to download. This works for any file size.