Split exports
Snapchat sent me several ZIP files. Which one do I use?
Updated
All of them, together. Snapchat splits a large archive into numbered parts (mydata~1786724342212.zip, then -2, -3 and so on), and only the first one contains the json folder with your dates and locations in it. The rest are nothing but media. Feed a tool a single part and you'll get exactly what you'd expect: a pile of files with no metadata to put back.
How to tell what you've got
Open the unnumbered one. It should hold four things: html, index.html, json and memories. The numbered parts hold only memories. If your first part has no json folder, then Export JSON Files wasn't ticked when you made the request, and no amount of combining parts will help. That one needs requesting again.
Don't unzip and merge them by hand
It's tempting, and it mostly works, but every part contains a folder called memories, so unzipping them side by side gives you memories, memories 2, memories 3 and so on rather than one merged folder. Merging those manually is where files get missed. Better to hand every ZIP over at once and let something else do the pooling.
Watch the count
It's normal for the JSON to list more memories than there are files. In one real export, 3,792 entries came with 3,639 media files behind them: about 4% that Snapchat listed and didn't ship. Those aren't recoverable by any tool; the files simply aren't in the archive. Worth knowing so you don't spend an evening hunting for them.
Give it all of them
This site takes every part at once and pools them, so the JSON from part one is applied to the media in parts two through seven. It runs in your browser and nothing is uploaded. The first 500 files are free.