I didn't dispute that. The key itself is fine. I'm just worried about using it for JSON retrieval! That part is undocumented as far as I can see, and therefore subject to change without notice
Huh. I thought that the Spreadsheet API was documented as an XML/JSON API, but it looks like only the XML is directly documented so ... poking around a bit more
The alt=json thing is a documented common feature of Google Data APIs, and the current Google Spreadsheets API is the target of the link in the list of Google Data APIs titled "Google Spreadsheets Data API". OTOH, the current v3 Spreadsheets API no longer has "Data" in the name, and there is a note on the Data APIs documentation that some Google Data APIs have been replaced with newer APIs that aren't Google Data APIs.
So, its at best an ambiguously-documented feature.
No, the key value for use in the API being the same that is displayed in the browser URL when working with the sheet is a documented feature:
https://developers.google.com/google-apps/spreadsheets/#retr...