First, check the size
A real .xd file is a ZIP package holding every artboard, the shared components and styles, and the embedded pictures, so even a small design is usually tens of kilobytes and a typical one is several megabytes. If the file you were sent is a few hundred bytes or a couple of kilobytes, it almost certainly isn’t the design: it’s a pointer, a link or a placeholder. If it is 0 bytes, it never finished downloading. Your computer shows the size in File Explorer’s details view or in the Finder’s Get Info window.
It’s a cloud document pointer
Since 2019 Adobe XD saves to Adobe’s cloud by default. A cloud document lives in the designer’s Creative Cloud account, and what sometimes gets copied or attached is a tiny file that only refers to it. It has no artboards inside, so nothing can draw it, not even XD on a computer signed in to a different account. The fix is on the sender’s side: ask them to open the design in XD, choose File › Save As and save it as a local document on their computer, then send you that .xd. If they only want you to look, an xd.adobe.com share link opens in any browser, but only as a web preview without the file.
It’s a link, not a file
Dragging a web address to the desktop makes a shortcut: an .url file on Windows or a .webloc file on a Mac. Renamed, or saved from a chat, it can end up called something.xd. It holds just the address. When Afterboard finds one it shows the address it points to, so you can open it in your browser. If that’s an Adobe share page, it’s a preview; ask for the .xd itself for layers, specs and exports.
It’s empty (0 bytes)
Cloud drives keep “online-only” placeholders on your computer that look like files but hold nothing until they download: OneDrive’s Files On-Demand, iCloud Drive with “Optimise Mac storage”, Dropbox online-only files and Creative Cloud Files. Make the file available offline (in OneDrive, right-click › Always keep on this device; in iCloud, click the download icon), wait for the cloud icon to go, and open it again. If it came by email, save the attachment again.
It’s cut short
A ZIP package keeps its table of contents at the very end, so a file that stopped downloading part-way can’t be read at all, even though it looks the right size at a glance. This happens with interrupted downloads, email systems that trim large attachments, and copies made while a cloud drive was still syncing. Download it again, or ask the sender to share it another way, such as a shared drive or a transfer service, or zipped.
It’s damaged
If the package opens but part of the design inside is unreadable, the file was changed or corrupted on the way. Ask for a fresh copy. If an older version exists, in a backup, a cloud drive’s version history or an earlier email, try that too.
It isn’t an XD file at all
Files get renamed. Afterboard looks at what is really inside and tells you if the “.xd” is actually a PDF (any PDF reader opens it), a PNG or JPEG picture (probably an exported artboard), a Photoshop .psd, or a RAR or 7-Zip archive that needs unpacking first. If a mail program or a download turned the design into a .zip, there’s nothing to do: drop the ZIP as it is and the .xd inside opens.
It asks for a password
XD itself never puts a password on a file, so the design was zipped with one afterwards. Ask the sender for the password, or for the file without it.
It opens but there’s nothing in it
An XD file can be valid and still empty: a new document that was saved before anything was drawn, or one saved while it was still syncing from the cloud. If only some artboards are missing, the page says how many the file lists but doesn’t contain. Either way, ask the designer to open the design in XD, check it looks complete, and save a local copy again.
When it does open
You get every artboard in a grid, a zoomable view with layers and an inspector, the document’s colours, text styles and fonts, and free SVG and PNG export one artboard at a time. A one-time £9 unlock exports everything at once as a PDF or a ZIP, with a handoff sheet. The file is read in your browser and isn’t uploaded, which also means none of the problems above is caused by a server: what you see is what is in the file.