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For me it has always been a part of the query parameter http://endpoint/item?format=json http://endpoint/item?format=json or ?type=json I never ever had a pro

For me it has always been a part of the query parameter http://endpoint/item?format=json http://endpoint/item?format=json or ?type=json I never ever had a problem with that. The only reason to use a file extension would be if the request would take no query parameters. It would never occur to me to use header information for this.

dgb23 3y ago
Both file extensions and query parameters are functionally very similar. What I don’t necessarily like about query params for this, is that their usage implies filtering. It’s a cultural assumption but it’s there. Another point: you might actually have a literal file at a similar path that you serve, typically when you cache responses (managed cache or straight from your app server). Using file extensions gives you a bit more natural affordances. It’s just overal less clunky.