Gmail does not block MOV files. Google publishes the complete list of file types Gmail refuses to attach — spelled out extension by extension — and not a single video or audio format appears on it. So when a .mov won't go out, the cause is size, storage, or an upload that never finished. It is not the format.
That distinction decides what you do next. A file blocked for its type needs converting; a file that is too big needs shrinking, or needs to stop being an attachment at all.
What Gmail actually blocks
Google's "File types blocked in Gmail" page states the rule directly: "To protect your account from potential viruses and harmful software, Gmail doesn't allow you to attach:" — and then names three things: "Certain types of files, including their compressed form (like .gz or .bz2 files) or when found within archives (like .zip or .tgz files)", "Documents with malicious macros", and "Password-protected archives with archived content".
The extension list is published in full:
.ade, .adp, .apk, .appx, .appxbundle, .bat, .cab, .chm, .cmd, .com, .cpl,
.diagcab, .diagcfg, .diagpkg, .dll, .dmg, .ex, .ex_, .exe, .hta, .img, .ins,
.iso, .isp, .jar, .jnlp, .js, .jse, .lib, .lnk, .mde, .mjs, .msc, .msi, .msix,
.msixbundle, .msp, .mst, .nsh, .pif, .ps1, .scr, .sct, .shb, .sys, .vb, .vbe,
.vbs, .vhd, .vxd, .wsc, .wsf, .wsh, .xll,Read it end to end: no .mov, no .mp4, no .mkv, no .mp3, no .wav. Gmail's own attachment help page makes the same point from the other side — the category it names is executables: "To prevent viruses, Gmail doesn't let you attach executable files, like files ending in .exe."
Two things on that list still matter to anyone moving footage around:
.imgand.isoare on it. Footage handed over as a disc image genuinely will not attach, and no amount of shrinking fixes that one.- The list moves. Google says so: "Gmail often updates the types of files not allowed to keep up with harmful software that is constantly changing." Treat the official page as the live copy, not this one.
The fastest fix: deal with the file before Gmail does
Since the format is not the gate, the file itself is what you have leverage over. Gmail's attachment page opens by naming this exact situation: "Add attachments, like files or photos, to your emails. To send large files over the size limit, like videos, use Google Drive."
Converting a QuickTime MOV to MP4 is the cheapest first move, because re-encoding is the step where you get any say over the output size. Drive's playback list treats the two as equals anyway — "MPEG4, 3GPP, and MOV files (h264 and MPEG4 video codecs; AAC audio codec)" — so the conversion costs you nothing if the file ends up as a Drive link.
Try it right here
Runs in your browser. Your file is not uploaded anywhere.
This runs inside your browser tab: the file is read from disk, re-encoded locally, and handed back, with nothing uploaded anywhere. If the result is still heavier than you want, compress it before attaching rather than after.
Other causes, in order of likelihood
1. The 25 MB cap is a total, not a per-file number
The limit itself is plain: "For personal Gmail accounts, the limit is 25 MB." What trips people up is what gets measured. Google's wording is "your total attachment size":
"If your total attachment size is greater than the limit, Gmail automatically removes the attachment and adds it as a Google Drive link in the email."
So a single clip well under 25 MB can still push a message over once there are three of them, or one clip plus a batch of photos. Each file passes on its own inspection; the message they share is what gets weighed. Chat apps do not all measure it this way, which is why the same file behaves differently in each place; see why Discord rejects a MOV for a contrast.
Note also what Google says happens at the limit: the attachment is removed and replaced with a Drive link, automatically. That is documented behaviour, not a failure. If your message flatly refuses to send instead, look at the next two causes.
2. Your Google storage is full
This one is badly underrated, because nothing about the error points at it. Gmail's help page is explicit:
"Attachments count toward your Google storage. Storage is shared across Drive, Photos, and Gmail. If you reach your storage limit, you can't send or receive attachments."
Drive's storage page says the same thing in wider terms: "When your account reaches its storage limit, you won't be able to upload or create files in Drive, send or receive emails in Gmail, or back up photos or videos to Google Photos." And the pool is shared — "Your Google Account comes with up to 15 GB of cloud storage at no charge", split across Drive, Gmail and Google Photos. A Drive full of old exports can be the reason a 6 MB MOV won't send.
3. It's a work or school account, so the number isn't yours
For personal accounts the 25 MB figure is Google's. For managed ones it isn't: "For work and school accounts, your Google Workspace administrator sets the attachment sending limits and attachment receiving limits."
The Workspace admin documentation lists sending limits of 25 MB for Business and Education editions, and for Enterprise: "Up to 50 MB** for Enterprise Plus and 25 MB for Enterprise Standard." Two footnotes on that table are not optional reading — the 50 MB figure is marked "Available only on the web version of Gmail", and all of those values are "the limits on the total size of the message content and attachments before encoding".
4. The upload simply hasn't finished
Gmail's troubleshooting section covers this case first: "If you upload files from another device, wait until the upload completes. Then send the attachments in your current message." For attachments that won't upload on desktop, the official steps are short:
Make sure you're using a supported browser.
Try adding the attachment in another browser.
If you've set up a web browser proxy, try disabling it.There is one network-level cause listed too: "Your network administrator or Internet provider probably blocked "mail-attachment.googleusercontent.com," the domain Google uses to host attachments." On a locked-down office or campus network, that is worth checking before you blame the file.
5. It sent — but the recipient can't open it
Once Gmail swaps your video for a Drive link, access stops being an email question and becomes a sharing-permission one. Google describes the check: "When you attach a Google Drive file to a message, Gmail checks to see if your recipients have access to the file. If they don't, you'll be prompted to change the sharing settings of the file before you send your message." If you keep the file private, "recipients won't be able to see it if" they have no Google Account, the address you used isn't a Google account, or they got the message through a mailing list.
How to tell it worked
Check the size on disk of everything you are attaching, added together — that total is the number Gmail reads. If the attachment shows up as a Drive link rather than a paperclip file, that is the documented over-limit behaviour and the message is fine. If sending still fails at any size, storage is the next thing to look at, not the file.
One thing worth knowing about what Google does not say: none of Gmail's attachment pages state that Gmail compresses or transcodes what you attach. Do not plan around it shrinking anything for you.
FAQ
Does Gmail block MOV files?
No. Google's published list of blocked extensions contains no video or audio formats — no .mov, .mp4, .mkv, .mp3 or .wav. It does include .img and .iso. Google notes the list is updated often, so check the official page for the current version.
Why does Gmail say my file is too large when it's under 25 MB? Because the limit is measured on "your total attachment size", not per file. Several clips, or a clip plus photos, add up into one number against the 25 MB cap for personal Gmail accounts.
What's the attachment limit on a work Gmail account? Your administrator sets it. Google's Workspace admin documentation lists 25 MB for Business and Education, and for Enterprise "Up to 50 MB** for Enterprise Plus and 25 MB for Enterprise Standard" — with the 50 MB tier available only on the web version of Gmail, and all values measured before encoding.
Does Gmail compress my video attachment? Google's official documentation doesn't state this anywhere. What it does document is that over the limit Gmail "automatically removes the attachment and adds it as a Google Drive link in the email." Convert or compress the file yourself first.
My MOV went out as a Drive link and the recipient can't open it. That's a Drive sharing-permission issue, not a Gmail one. Gmail checks recipient access before sending and prompts you to change the sharing settings; a file kept private stays unreadable to anyone without a Google Account, anyone whose address isn't a Google account, and anyone who received it via a mailing list.
Start with MOV to MP4, which runs entirely in your browser, and browse all Clapr tools or the rest of the fix guides if the file still won't cooperate.
Attachment and storage rules cited from Google's Gmail and Drive help pages, checked 16 September 2026. Google changes these without notice — verify against the official documentation before relying on them.
