A wedding hashtag used to be the standard way to gather guest photos. A QR code on the tables is the newer one. They solve different problems, and many couples use both.
How a wedding hashtag works
You pick a unique tag, print it on your signs, and guests add it when they post. Afterwards you search the hashtag to find the photos.
Where hashtags fall short
Posts from private accounts don't appear in hashtag search, so many of your friends' photos never show up. Guests tag only what they choose to post publicly, usually a few favorites rather than everything they took. Many forget the tag. And you see the photos inside the app; you don't get the original files to print or keep.
How a QR code works
Guests scan the code with their phone camera and upload straight to your gallery, whether or not they post anywhere. You get every photo and video they choose to share, in original quality, without asking anyone to post online.
Hashtag or QR code?
Use a hashtag if you want public posts and a bit of buzz on social media.
Use a QR code if you want the photos themselves: every guest's shots, private ones included, in one place you can download.
Using both
Put both on one sign: the QR code for sharing photos with you, and the hashtag for anyone posting publicly. Keep the instructions short so the sign stays easy to read.
Making the QR code work
Put a code on every table and at the bar, mention it once during the speeches, and play the live slideshow so guests see their photos appear. Those three steps make the biggest difference.