Written by the founder of BreezeConvert — a creative director working across set design, game 3D, Unreal/VFX and AI content pipelines. More about the author.
Almost everyone has hit it: you attach a file, click send, and the message bounces back with "attachment too large." It's always at the wrong moment. The fix is usually quick once you understand two things — what the real limits are, and why your file is bigger than it needs to be. Then it's just a matter of shrinking the right part.
The limits you're actually up against
Different systems draw the line in different places, and it's the recipient's limit as much as yours that matters. Gmail caps attachments at 25 MB. Outlook / Microsoft 365 is commonly 20–25 MB but many corporate setups tighten it to 10 MB. Plenty of business mail servers sit at 10 MB, and application portals or government upload forms are often the strictest at 5 MB or less. When in doubt, aim under 10 MB and you'll clear most inboxes.
One non-obvious trap: attachments inflate in transit. Email encodes attachments in a way (base64) that adds roughly a third to their size on the wire. So a file that reads 9.8 MB on disk can arrive as ~13 MB and bounce against a 10 MB limit. Always leave yourself headroom — target comfortably below the cap, not right at it.
First, figure out what kind of file it is
The right fix depends entirely on what's making the file big, so identify that first. Most oversized attachments fall into three buckets: a PDF (usually heavy because of high-resolution images or scanned pages), a photo or image (print-resolution data you don't need on a screen), or a video (big by nature). Each has its own tool, and using the wrong approach — say, zipping a PDF that's already compressed internally — barely helps.
Shrinking a PDF
PDFs are the most common culprit, and usually the easiest win. If the size comes from images or scanned pages, re-compressing them cuts the file dramatically. Our PDF compressor does this in your browser; start at the medium level, check the result, and step up only if you still need to. One caveat worth knowing: heavy compression rasterises pages, so the text stops being selectable — fine for a portfolio or a scan, but keep the original for anything that needs to stay searchable. The full PDF guide covers the trade-offs.
Shrinking a photo or image
A photo straight from a phone or camera carries far more resolution than any screen needs, so it compresses well with no visible loss. The image compressor handles this; you can often cut a multi-megabyte photo by 70–80% and still have it look perfect in an email. If the image is a HEIC from an iPhone, convert it to JPG first (see the HEIC guide), and if you're attaching several, shrinking each one is usually enough to clear the limit for the whole message.
Shrinking a video
Video is the hardest to fit in an email, because even a short clip is large. The video compressor re-encodes to a smaller MP4 and can drop the resolution, which often halves the size or better for a short clip. But be realistic: a long video won't fit in an email no matter what, and the honest answer there is a share link (upload it somewhere and send the link) rather than an attachment.
The fallback that always works
If a file simply won't shrink enough — a long video, a huge design file — stop fighting the attachment and send a link instead. Upload to any file-sharing service and paste the link into the email. It sidesteps the limit entirely, doesn't clog the recipient's inbox, and lets you send things far larger than any mail server allows.
A note on privacy while you're at it: the files people email are often the sensitive ones — contracts, medical scans, personal photos. Every compressor linked here runs entirely in your browser, so shrinking a file to fit doesn't mean uploading it to a stranger first. You can verify that yourself before trusting it with anything private.